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1.
Many plant species can be induced to flower by responding to stress factors. The short-day plants Pharbitis nil and Perilla frutescens var. crispa flower under long days in response to the stress of poor nutrition or low-intensity light. Grafting experiments using two varieties of P. nil revealed that a transmissible flowering stimulus is involved in stress-induced flowering. The P. nil and P. frutescens plants that were induced to flower by stress reached anthesis, fruited and produced seeds. These seeds germinated, and the progeny of the stressed plants developed normally. Phenylalanine ammonialyase inhibitors inhibited this stress-induced flowering, and the inhibition was overcome by salicylic acid (SA), suggesting that there is an involvement of SA in stress-induced flowering. PnFT2, a P. nil ortholog of the flowering gene FLOWERING LOCUS T (FT) of Arabidopsis thaliana, was expressed when the P. nil plants were induced to flower under poor-nutrition stress conditions, but expression of PnFT1, another ortholog of FT, was not induced, suggesting that PnFT2 is involved in stress-induced flowering.Key words: flowering, stress, phenylalanine ammonia-lyase, salicylic acid, FLOWERING LOCUS T, Pharbitis nil, Perilla frutescensFlowering in many plant species is regulated by environmental factors, such as night-length in photoperiodic flowering and temperature in vernalization. On the other hand, a short-day (SD) plant such as Pharbitis nil (synonym Ipomoea nil) can be induced to flower under long days (LD) when grown under poor-nutrition, low-temperature or high-intensity light conditions.19 The flowering induced by these conditions is accompanied by an increase in phenylalanine ammonia-lyase (PAL) activity.10 Taken together, these facts suggest that the flowering induced by these conditions might be regulated by a common mechanism. Poor nutrition, low temperature and high-intensity light can be regarded as stress factors, and PAL activity increases under these stress conditions.11 Accordingly, we assumed that such LD flowering in P. nil might be induced by stress. Non-photoperiodic flowering has also been sporadically reported in several plant species other than P. nil, and a review of these studies suggested that most of the factors responsible for flowering could be regarded as stress. Some examples of these factors are summarized in 1214

Table 1

Some cases of stress-induced flowering
Stress factorSpeciesFlowering responseReference
high-intensity lightPharbitis nilinduction5
low-intensity lightLemna paucicostatainduction29
Perilla frutescens var. crispainduction14
ultraviolet CArabidopsis thalianainduction23
droughtDouglas-firinduction30
tropical pasture Legumesinduction31
lemoninduction3235
Ipomoea batataspromotion36
poor nutritionPharbitis nilinduction3, 4, 13
Macroptilium atropurpureumpromotion37
Cyclamen persicumpromotion38
Ipomoea batataspromotion36
Arabidopsis thalianainduction39
poor nitrogenLemna paucicostatainduction40
poor oxygenPharbitis nilinduction41
low temperaturePharbitis nilinduction9, 12
high conc. GA4/7Douglas-firpromotion42
girdlingDouglas-firinduction43
root pruningCitrus sp.induction44
Pharbitis nilinduction45
mechanical stimulationAnanas comosusinduction46
suppression of root elongationPharbitis nilinduction7
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2.
3.
4.
The enzymes called lipoxygenases (LOXs) can dioxygenate unsaturated fatty acids, which leads to lipoperoxidation of biological membranes. This process causes synthesis of signaling molecules and also leads to changes in cellular metabolism. LOXs are known to be involved in apoptotic (programmed cell death) pathway, and biotic and abiotic stress responses in plants. Here, the members of LOX gene family in Arabidopsis and rice are identified. The Arabidopsis and rice genomes encode 6 and 14 LOX proteins, respectively, and interestingly, with more LOX genes in rice. The rice LOXs are validated based on protein alignment studies. This is the first report wherein LOXs are identified in rice which may allow better understanding the initiation, progression and effects of apoptosis, and responses to bitoic and abiotic stresses and signaling cascades in plants.Key words: apoptosis, biotic and abiotic stresses, genomics, jasmonic acid, lipidsLipoxygenases (linoleate:oxygen oxidoreductase, EC 1.13.11.-; LOXs) catalyze the conversion of polyunsaturated fatty acids (lipids) into conjugated hydroperoxides. This process is called hydroperoxidation of lipids. LOXs are monomeric, non-heme and non-sulfur, but iron-containing dioxygenases widely expressed in fungi, animal and plant cells, and are known to be absent in prokaryotes. However, a recent finding suggests the existence of LOX-related genomic sequences in bacteria but not in archaea.1 The inflammatory conditions in mammals like bronchial asthama, psoriasis and arthritis are a result of LOXs reactions.2 Further, several clinical conditions like HIV-1 infection,3 disease of kidneys due to the activation of 5-lipoxygenase,4,5 aging of the brain due to neuronal 5-lipoxygenase6 and atherosclerosis7 are mediated by LOXs. In plants, LOXs are involved in response to biotic and abiotic stresses.8 They are involved in germination9 and also in traumatin and jasmonic acid biochemical pathways.10,11 Studies on LOX in rice are conducted to develop novel strategies against insect pests12 in response to wounding and insect attack,13 and on rice bran extracts as functional foods and dietary supplements for control of inflammation and joint health.14 In Arabidopsis, LOXs are studied in response to natural and stress-induced senescence,15 transition to flowering,16 regulation of lateral root development and defense response.17The arachidonic, linoleic and linolenic acids can act as substrates for different LOX isozymes. A hydroperoxy group is added at carbons 5, 12 or 15, when arachidonic acid is the substrate, and so the LOXs are designated as 5-, 12- or 15-lipoxygenases. Sequences are available in the database for plant lipoxygenases (EC:1.13.11.12), mammalian arachidonate 5-lipoxygenase (EC:1.13.11.34), mammalian arachidonate 12-lipoxygenase (EC:1.13.11.31) and mammalian erythroid cell-specific 15-lipoxygenase (EC:1.13.11.33). The prototype member for LOX family, LOX-1 of Glycine max L. (soybean) is a 15-lipoxygenase. The LOX isoforms of soybean (LOX-1, LOX-2, LOX-3a and LOX-3b) are the most characterized of plant LOXs.18 In addition, five vegetative LOXs (VLX-A, -B, -C, -D, -E) are detected in soybean leaves.19 The 3-dimensional structure of soybean LOX-1 has been determined.20,21 LOX-1 was shown to be made of two domains, the N-terminal domain-I which forms a β-barrel of 146 residues, and a C-terminal domain-II of bundle of helices of 693 residues21 (Fig. 1). The iron atom was shown to be at the centre of domain-II bound by four coordinating ligands, of which three are histidine residues.22Open in a separate windowFigure 1Three-dimensional structure of soybean lipoxygenase L-1. The domain I (N-terminal) and domain II (C-terminal) are indicated. The catalytic iron atom is embedded in domain II (PDB ID-1YGE).21This article describes identification of LOX genes in Arabidopsis and rice. The Arabidopsis genome encodes for six LOX proteins23 (www.arabidopsis.org) (
LocusAnnotationNomenclatureA*B*C*
AT1G55020lipoxygenase 1 (LOX1)LOX185998044.45.2049
AT1G17420lipoxygenase 3 (LOX3)LOX3919103725.18.0117
AT1G67560lipoxygenase family proteinLOX4917104514.68.0035
AT1G72520lipoxygenase, putativeLOX6926104813.17.5213
AT3G22400lipoxygenase 5 (LOX5)LOX5886101058.86.6033
AT3G45140lipoxygenase 2 (LOX2)LOX2896102044.75.3177
Open in a separate window*A, amino acids; B, molecular weight; C, isoelectric point.Interestingly, the rice genome (rice.plantbiology.msu.edu) encodes for 14 LOX proteins as compared to six in Arabidopsis (and22). Of these, majority of them are composed of ∼790–950 aa with the exception for loci, LOC_Os06g04420 (126 aa), LOC_Os02g19790 (297 aa) and LOC_Os12g37320 (359 aa) (Fig. 2).Open in a separate windowFigure 2Protein alignment of rice LOXs and vegetative lipoxygenase, VLX-B,28 a soybean LOX (AA B67732). The 14 rice LOCs are indicated on left and sequence position on right. Gaps are included to improve alignment accuracy. Figure was generated using ClustalX program.

Table 2

Genes encoding lipoxygenases in rice
ChromosomeLocus IdPutative functionA*B*C*
2LOC_Os02g10120lipoxygenase, putative, expressed9271035856.0054
2LOC_Os02g19790lipoxygenase 4, putative29733031.910.4799
3LOC_Os03g08220lipoxygenase protein, putative, expressed9191019597.4252
3LOC_Os03g49260lipoxygenase, putative, expressed86897984.56.8832
3LOC_Os03g49380lipoxygenase, putative, expressed87898697.57.3416
3LOC_Os03g52860lipoxygenase, putative, expressed87197183.56.5956
4LOC_Os04g37430lipoxygenase protein, putative, expressed79889304.610.5125
5LOC_Os05g23880lipoxygenase, putative, expressed84895342.97.6352
6LOC_Os06g04420lipoxygenase 4, putative12614054.76.3516
8LOC_Os08g39840lipoxygenase, chloroplast precursor, putative, expressed9251028196.2564
8LOC_Os08g39850lipoxygenase, chloroplast precursor, putative, expressed9421044947.0056
11LOC_Os11g36719lipoxygenase, putative, expressed86998325.45.3574
12LOC_Os12g37260lipoxygenase 2.1, chloroplast precursor, putative, expressed9231046876.2242
12LOC_Os12g37320lipoxygenase 2.2, chloroplast precursor, putative, expressed35940772.78.5633
Open in a separate window*A, amino acids; B, molecular weight; C, isoelectric point.

Table 3

Percent homology of rice lipoxygenases against Arabidopsis
Loci (Os)Homolog (At)Identity/similarity (%)No. of aa compared
LOC_Os02g10120LOX260/76534
LOC_Os02g19790LOX554/65159
LOC_Os03g08220LOX366/79892
LOC_Os03g49260LOX556/73860
LOC_Os03g49380LOX560/75861
LOC_Os03g52860LOX156/72877
LOC_Os04g37430LOX361/75631
LOC_Os05g23880LOX549/66810
LOC_Os06g04420LOX549/62114
LOC_Os08g39840LOX249/67915
LOC_Os08g39850LOX253/70808
LOC_Os11g36719LOX552/67837
LOC_Os12g37260LOX253/67608
LOC_Os12g37320LOX248/60160
Open in a separate windowOs, Oryza sativa L.; At, Arabidopsis thaliana L.; aa, amino acids.In plants, programmed cell death (PCD) has been linked to different stages of development and senescence, germination and response to cold and salt stresses.24,25 To conclude, this study indicates that rice genome encodes for more LOX proteins as compared to Arabidopsis. The LOX members are not been thoroughly investigated in rice. The more advanced knowledge on LOXs function might spread light on the significant role of LOXs in PCD, biotic and abiotic stress responses in rice.  相似文献   

5.
Allelic frequency and genotypes of prion protein at codon 136 and 171 in Iranian Ghezel sheep breeds     
Siamak Salami  Reza Ashrafi Zadeh  Mir Davood Omrani  Fatemeh Ramezani  Amir Amniattalab 《朊病毒》2011,5(3):228-231
PrP genotypes at codons 136 and 171 in 120 Iranian Ghezel sheep breeds were studied using allele-specific PCR amplification and compared with the well-known sheep breeds in North America, the United States and Europe. The frequency of V allele and VV genotype at codon 136 of Ghezel sheep breed was significantly lower than AA and AV. At codon 171, the frequency of allele H was significantly lower than Q and R. Despite the similarities of PrP genotypes at codons 136 and 171 between Iranian Ghezel sheep breeds and some of the studied breeds, significant differences were found with others. Planning of effective breeding control and successful eradication of susceptible genotypes in Iranian Ghezel sheep breeds will not be possible unless the susceptibility of various genotypes in Ghezel sheep breeds to natural or experimental scrapie has been elucidated.Key words: scrapie, Ghezel sheep breed, PrP genotyping, allele specific amplification, codon 136, codon 171Scrapie was first described in England in 1732,1 and it is an infectious neurodegenerative fatal disease of sheep and goats belonging to the group of transmissible subacute spongiform encephalopathies (TSEs), along with bovine spongiform encephalopathy (BSE), chronic wasting disease and Creutzfeldt-Jakob disease.2,3 The term prion, proteinaceous infectious particles, coined by Stanley B. Prusiner, was introduced, and he presents the idea that the causal agent is a protein.4 Prion proteins are discovered in two forms, the wild-type form (PrPc) and the mutant form (PrPSc).5 Although scrapie is an infectious disease, the susceptibility of sheep is influenced by genotypes of the prion protein (PrP) gene.2,6 Researchers have found that the PrP allelic variant alanine/arginine/arginine (ARR) at codons 136, 154 and 171 is associated with resistance to scrapie in several breeds.714 Most of the sheep populations in the Near East and North African Region (84% of the total population of 255 million) are raised in Iran, Turkey, Pakistan, Sudan, Algeria, Morocco, Afghanistan, Syria and Somalia.15 In 2003, the Iranian sheep population was estimated at 54,000,000 head. The Ghezel sheep breed, which also is known as Kizil-Karaman, Mor-Karaman, Dugli, Erzurum, Chacra, Chagra, Chakra, Gesel, Gezel, Kazil, Khezel, Khizel, Kizil, Qezel, Qizil and Turkish Brown, originated in northwestern Iran and northeastern Turkey. By considering sheep breeds as one of the main sources of meat, dairy products and related products, a global screening attempt is started in different areas. In compliance with European Union Decision 2003/100/EC, each member state has introduced a breeding program to select for resistance to TSEs in sheep populations to increase the frequency of the ARR allele. A similar breeding program is established in United States and Canada. The Near East and North African Region still needs additional programs to help the global plan of eradication of scrapie-susceptible genotypes. The current study was the first to assess the geographical and molecular variation of codons 136 and 171 polymorphism between Iranian Ghezel sheep breed and well-known sheep breeds.Polymorphism at codon 136 is associated with susceptibility to scrapie in both experimental and natural models.10,11,13,16 17 and Austrian Carynthian sheep.18 Swiss White Alpine showed higher frequency of allele V at position 136 than Swiss Oxford Down, Swiss Black-Brown Mountain and Valais Blacknose.19 Comparison of polymorphism at codon 136 in the current study with some of other breeds (20 some flock of Hampshire sheep21 with current study, but the frequency of it is higher than that of some other breeds.

Table 1

Comparison of PrP allelic and genotype frequencies at codon 136 in different breeds
BreedA (%)V (%)AA (%)AV (%)VV (%)Reference
Iranian Ghezel breeds (n = 120)77.5022.565.0025.0010.00Current study
Oklahoma sheep (n = 334)De Silva, et al.27
Suffolk99.240.7698.481.520.00
Hampshire1000.001000.000.00
Dorset92.67.9487.309.523.17
Montadale77.6622.3459.5736.174.26
Hampshire (n = 48)93.756.2588.0012.000.00Youngs, et al.21
German Sheep Breeds (n = 660)92.897.1187.8010.471.73Kutzer, et al.28
Bleu du Maine83.4716.5369.5627.832.61
Friesian Milk S.1000.001000.000.00
Nolana90.139.8785.908.465.64
Suffolk1000.001000.000.00
Texel90.879.1382.1617.410.43
Swiss Sheep (n = 200)92.57.5Gmur, et al.19
Swiss Oxford Down93.007.00---
Swiss Black-Brown M.99.001.00---
Valais Blacknose1000.00---
Swiss White Alpine88.0022.00---
Austrian Sheep (n = 112)98.951.0598.950.001.05Sipos, et al.18
Tyrolean mountain sheep1000.001000.000.00
Forest sheep1000.001000.000.00
Tyrolean stone sheep1000.001000.000.00
Carynthian sheep95.804.2095.800.004.20
Open in a separate windowIt has been found that a polymorphism at codon 171 also is associated with susceptibility to experimental scrapie in Cheviot sheep16 and natural scrapie in Suffolk sheep.22 As shown in 23 They also found that different breeds show different predominant genotypes in ewes and rams.23 Different PrP genotypes were found at codon 171 in Austrian sheep breeds, but QQ has higher frequency than others.18 In some kinds of Swiss breeds, allelic frequencies of allele Q was higher than R.19 Distribution of prion protein codon 171 genotypes in Hampshire sheep revealed that different flocks shows different patterns.21 The frequency of PrP genotypes at codon 171 in Iranian Ghezel breeds was similar to some sheep breeds, like the Suffolk breed of Oklahoma sheep, but it was completely different from others (PrP genotypes at codon 172BreedAllelic frequencyGenotypesReferenceQRHRRQRQQQHRHHHIranian Iranian Ghezel breeds (n = 120)55.0043.331.6723.3336.6736.670.003.330.00Current studyOklahoma sheep (n = 334)De Silva, et al.20Suffolk40.9559.050.0037.0743.9718.970.000.000.00Hampshire51.8948.110.0021.7052.8325.470.000.000.00Dorset67.7531.250.007.9546.5945.450.000.000.00Montadale62.9637.040.0014.8144.4440.740.000.000.00Hampshire (n = 201)72.1426.601.265.0042.0050.002.001.000.00Youngs, et al.21German Sheep Breeds (n = 660)Kutzer, et al.28Bleu du Maine37.862.20.0046.9630.4422.60.000.000.00Friesian Milk S.90.458.90.651.2715.382.80.000.000.64Nolana42.357.80.0036.6242.2621.130.000.000.00Suffolk68.427.64.016.121.8455.174.61.151.15Texel55.3529.714.912.5626.8336.3611.257.365.63Swiss Sheep (n = 200)Gmur, et al.19Swiss Oxford Down32.0068.00-------Swiss Black-Brown M.70.0030.00-------Valais Blacknose85.0015.00-------Swiss White Alpine27.0073.00-------Austrian Sheep (n = 112)Sipos, et al.18Tyrolean mountain sheep74.3025.800.002.9045.7051.400.000.000.00Forest sheep77.0019.203.8011.5015.4069.200.000.003.80Tyrolean stone sheep81.5014.803.700.0029.6062.907.400.000.00Carynthian sheep72.8023.004.204.2041.7013.008.400.000.00Open in a separate windowThe association between scrapie susceptibility and polymorphism at codon154 is unclear, and fewer evidences were found that support it.24,25 So the frequency of different genotypes at codon 154 in Iranian Sheep breeds has not been included in the current study.In addition to difference in number of included animals and methodology of genotyping, the apparent discrepancies among reported allelic frequency might be caused by the difference in geographical dissemination of sheep breeds and related purity.26 The deviations from Hardy-Weinberg equilibrium, which were assumed in the current study, were checked using Pearson''s chi-squared test or Fisher''s exact test. Although the number of animals in this study is acceptable, a population study is still suggested. In conclusion, fairly different patterns of PrP genotypes in this common Near eastern sheep breed are an evidence for geographical variation of molecular susceptibility to scrapie. Because other report from Turkey also has shown a prevalence of genotypes, which is different from western countries,26 and no reports have been published yet to show which of the genotypes in that breed are actually resistant or susceptible to natural or experimental scrapie, our results is an authentic platform to motivate further studies. Actually, extrapolation of the existing general pattern of susceptibility or resistance for all breeds and current plan of elimination would not be successful unless the susceptible genotypes in the Near East with numerous breeds will be identified. Hence, the current study could be used as an important pilot study for further investigation.Genomic DNA was isolated from fresh EDTA-treated blood of 120 healthy, randomly chosen sheep of Iranian Ghezel sheep breeds using a mammalian blood DNA isolation kit (Bioflux, Japan). The allelic frequencies of prion protein codons 171 and 136 were determined by allele-specific PCR amplifications using scrapie susceptibility test kit (Elchrom Scientific AG). Primer sets were designed by manufacturer to amplify specific gene targets according to possible genotypes of positions 136 and 171.The amplification reactions were performed using iCycler™ (BioRad Inc.,), and PCR products (PositionGenotypeFragment size136A133136V139171H170171Q247171R155Open in a separate window  相似文献   

6.
Gene silencing to investigate the roles of receptor-like proteins in Arabidopsis     
Ursula Ellendorff  Zhao Zhang  Bart PHJ Thomma 《Plant signaling & behavior》2008,3(10):893-896
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7.
Multiple roles for cytokinin receptors and cross-talk of signaling pathways     
Teodoro Coba de la Pe?a  Claudia B Cárcamo  M Mercedes Lucas  José J Pueyo 《Plant signaling & behavior》2008,3(10):791-794
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8.
Tomato BRI1 and systemin wound signalling     
Nicholas Holton  Kate Harrison  Takao Yokota  Gerard J Bishop 《Plant signaling & behavior》2008,3(1):54-55
Brassinosteroids (BRs) are perceived by Brassinosteroid Insensitive 1 (BRI1), that encodes a leucine-rich repeat receptor kinase. Tomato BRI1 has previously been implicated in both systemin and BR signalling. The role of tomato BRI1 in BR signalling was confirmed, however it was found not to be essential for systemin/wound signalling. Tomato roots were shown to respond to systemin but this response varied according to the species and growth conditions. Overall the data indicates that mutants defective in tomato BRI1 are not defective in systemin-induced wound signalling and that systemin perception can occur via a non-BRI1 mechanism.Key words: tomato BRI1, brassinosteroids, systemin, wound signallingBrassinosteroids (BRs) are steroid hormones that are essential for normal plant growth. The most important BR receptor in Arabidopsis is BRASSINOSTERIOD INSENSITIVE 1 (BRI1), a serine/threonine kinase with a predicted extracellular domain of ∼24 leucine-rich repeats (LRRs).1,2 BRs bind to BRI1 via a steroid-binding domain that includes LRR 21 and a so-called “island” domain.2,3 In tomato a BRI1 orthologue has been identified that when mutated, as in the curl3 (cu3) mutation, results in BR-insensitive dwarf plants.4 Tomato BRI1 has also been purified as a systemin-binding protein.5 Systemin is an eighteen amino acid peptide, which is produced by post-translational cleavage of prosystemin. Systemin has been implicated in wound signalling and is able to induce the production of jasmonate, protease inhibitors (PIN) and rapid alkalinization of cell suspensions (reviewed in ref. 6).To clarify whether tomato BRI1 was indeed a dual receptor it was important to first confirm its role in BR signalling. Initially this was carried out by genetic complementation of the cu3 mutant phenotype.7 Overexpression of tomato BRI1 restored the dwarf phenotype and BR sensitivity and normalized BR levels (35S:TomatoBRI1 complemented lineWt*cu3*6-deoxocathasterone5669646766-deoxoteasteronend47483-dehydro-6-deoxoteasterone8762696-deoxotyphasterolnd5884226-deoxocastasterone1,7556,24726,210castasterone25563717,428brassinolidendndndOpen in a separate windowBR content ng/kg fw.*Montoya et al.4 nd, not detected.To show the role of tomato BRI1 in systemin signalling tomato BR mutants and the complemented line were tested for their systemin response. Tomato cu3 mutants were shown not to be defective in systemin-induced proteinase inhibitor (PIN) gene induction, nor were they defective in PIN gene induction in response to wounding. Cell suspensions made from cu3 mutant tissue exhibited an alkalinization of culture medium similar to wild-type cell suspension. These data taken together indicated that BRI1 was not essential for systemin signalling. However, Scheer et al.8 demonstrated that the overexpression of tomato BRI1 in tobacco suspension cultures results in an alkalinization in response to systemin, which was not observed in untransformed cultures. This suggests that BRI1 is capable of eliciting systemin responsiveness and that in tomato BRI1 mutants another mechanism is functioning to enable systemin signalling.Root elongation is a sensitive bioassay for BR action with BRs inhibiting root growth. Solanum pimpinellifolium roots elongate in response to systemin, in a BRI1-dependent fashion. In Solanum lycopersicum root length was reduced in response to systemin and BR and jasmonate synthesis mutants indicated that the inhibition did not require jasmonates or BRs. Normal ethylene signalling was required for the root response to systemin. When a tobacco, Nicotiana benthamiana, BRI1 orthologue was transformed into cu3 both the dwarfism and systemin-induced root elongation was restored to that of wild type. Tobacco plants however do not respond to systemin. This is puzzling as the introduction of tomato BRI1 into tobacco enabled systemin responsiveness.8 Further investigation as to how tomato BRI1 elicits this response is therefore required.Systemin has been demonstrated to bind to two tomato proteins BRI1/SR1605 and SBP50.9 The data presented by Holton et al.7 indicates that tomato BRI1 is not essential for systemin-induced wound responses and that a non-BRI1 pathway is present that is able to facilitate a systemin response. Whether this is via a related LRR receptor kinase or by another protein remains to be elucidated.  相似文献   

9.
Nooks and Crannies in Type VI Secretion Regulation     
Christophe S. Bernard  Yannick R. Brunet  Erwan Gueguen  Eric Cascales 《Journal of bacteriology》2010,192(15):3850-3860
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10.
De novo mammalian prion synthesis     
Federico Benetti  Giuseppe Legname 《朊病毒》2009,3(4):213-219
Prions are responsible for a heterogeneous group of fatal neurodegenerative diseases. They can be sporadic, genetic, or infectious disorders involving post-translational modifications of the cellular prion protein (PrPC). Prions (PrPSc) are characterized by their infectious property and intrinsic ability to convert the physiological PrPC into the pathological form, acting as a template. The “protein-only” hypothesis, postulated by Stanley B. Prusiner, implies the possibility to generate de novo prions in vivo and in vitro. Here we describe major milestones towards proving this hypothesis, taking into account physiological environment/s, biochemical properties and interactors of the PrPC.Key words: prion protein (PrP), prions, amyloid, recombinant prion protein, transgenic mouse, protein misfolding cyclic amplification (PMCA), synthethic prionPrions are responsible for a heterogeneous group of fatal neurodegenerative diseases (1 They can be sporadic, genetic or infectious disorders involving post-translational modifications of the cellular prion protein (PrPC).2 Prions are characterized by their infectious properties and by their intrinsic ability to encipher distinct biochemical properties through their secondary, tertiary and quaternary protein structures. In particular, the transmission of the disease is due to the ability of a prion to convert the physiological PrPC into the pathological form (PrPSc), acting as a template.3 The two isoforms of PrP appear to be different in terms of protein structures, as revealed by optical spectroscopy experiments such as Fourier-transform infrared and circular dichroism.4 PrPC contains 40% α-helix and 3% β-sheet, while the pathological isoform, PrPSc, presents approximately 30% α-helix and 45% β-sheet.4,5 PrPSc differs from PrPC because of its altered physical-chemical properties such as insolubility in non-denaturing detergents and proteinases resistance.2,6,7

Table 1

The prion diseases
Prion diseaseHostMechanism
iCJDhumansinfection
vCJDhumansinfection
fCJDhumansgenetic: octarepeat insertion, D178N-129V, V180I, T183A, T188K, T188R-129V, E196K, E200K, V203I, R208H, V210I, E211Q, M232R
sCJDhumans?
GSShumansgenetic: octarepeat insertion, P102L-129M, P105-129M, A117V-129V, G131V-129M, Y145*-129M, H197R-129V, F198S-129V, D202N-129V, Q212P, Q217R-129M, M232T
FFIhumansgenetic: D178-129M
Kurufore peopleinfection
sFIhumans?
Scrapiesheepinfection
BSEcattleinfection
TMEminkinfection
CWDmule deer, elkcontaminated soils?
FSEcatsinfection
Exotic ungulate encephalopathygreater kudu, nyala, oryxinfection
Open in a separate windowi, infective form; v, variant; f, familial; s, sporadic; CJD, Creutzfeldt-Jakob disease; GSS, Gerstmann-Straüssler-Sheinker disease; FFI, fatal familial insomnia; sFI, sporadic fatal insomnia; BSE, bovine spongiform encephalopathy; TME, transmissible mink encephalopathy; CWD, chronic wasting disease; FSE, feline spongiform encephalopathy.73,78The prion conversion occurring in prion diseases seems to involve only conformational changes instead of covalent modifications. However, Mehlhorn et al. demonstrated the importance of a disulfide bond between the two cysteine residues at position 179 and 214 (human (Hu) PrP numbering) to preserve PrP into its physiological form. In the presence of reducing conditions and pH higher than 7, recombinant (rec) PrP tends to assume high β-sheet content and relatively low solubility like PrPSc.8  相似文献   

11.
Towards elucidating the differential regulation of floral and extrafloral nectar secretion     
Venkatesan Radhika  Christian Kost  Wilhelm Boland  Martin Heil 《Plant signaling & behavior》2010,5(7):924-926
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12.
Aluminum induced proteome changes in tomato cotyledons     
Suping Zhou  Roger Sauve  Theodore W Thannhauser 《Plant signaling & behavior》2009,4(8):769-772
Cotyledons of tomato seedlings that germinated in a 20 µM AlK(SO4)2 solution remained chlorotic while those germinated in an aluminum free medium were normal (green) in color. Previously, we have reported the effect of aluminum toxicity on root proteome in tomato seedlings (Zhou et al.1). Two dimensional DIGE protein analysis demonstrated that Al stress affected three major processes in the chlorotic cotyledons: antioxidant and detoxification metabolism (induced), glyoxylate and glycolytic processes (enhanced), and the photosynthetic and carbon fixation machinery (suppressed).Key words: aluminum, cotyledons, proteome, tomatoDifferent biochemical processes occur depending on the developmental stages of cotyledons. During early seed germination, before the greening of the cotyledons, glyoxysomes enzymes are very active. Fatty acids are converted to glucose via the gluconeogenesis pathway.2,3 In greening cotyledons, chloroplast proteins for photosynthesis and leaf peroxisomal enzymes in the glycolate pathway for photorespiration are metabolized.24 Enzymes involved in regulatory mechanisms such as protein kinases, protein phosphatases, and mitochondrial enzymes are highly expressed.3,5,6The chlorotic cotyledons are similar to other chlorotic counterparts in that both contains lower levels of chlorophyll, thus the photosynthetic activities are not as active. In order to understand the impact of Al on tomato cotyledon development, a comparative proteome analysis was performed using 2D-DIGE following the as previously described procedure.1 Some proteins accumulated differentially in Al-treated (chlorotic) and untreated cotyledons (Fig. 1). Mass spectrometry of tryptic digestion fragments of the proteins followed by database search has identified some of the differentially expressed proteins (Open in a separate windowFigure 1Image of protein spots generated by Samspot analysis of Al treated and untreated tomato cotyledons proteomes separated on 2D-DIGE.

Table 1

Proteins identified from tomato cotyledons of seeds germinating in Al-solution
Spot No.Fold (treated/ctr)ANOVA (p value)AnnotationSGN accession
12.340.00137412S seed storages protein (CRA1)SGN-U314355
22.130.003651unidentified
32.00.006353lipase class 3 familySGN-U312972
41.960.002351large subunit of RUBISCOSGN-U346314
51.952.66E-05arginine-tRNA ligaseSGN-U316216
61.950.003343unidentified
71.780.009219Monodehydroascorbate reductase (NADH)SGN-U315877
81.780.000343unidentified
91.754.67E-05unidentified
121.700.002093unidentified
131.680.004522unidentified
151.660.019437Glutamate dehydrogenase 1SGN-U312368
161.660.027183unidentified
171.622.01E-08Major latex protein-related, pathogenesis-relatedSGN-U312368
18−1.610.009019RUBisCo activaseSGN-U312543
191.610.003876Cupin family proteinSGN-U312537
201.600.000376unidentified
221.590.037216unidentified
0.003147unidentified
29−1.560.001267RUBisCo activaseSGN-U312543
351.520.001955unidentified
401.470.007025unidentified
411.470.009446unidentified
451.450.001134unidentified
59−1.405.91E-0512 S seed storage proteinSGN-U314355
611.391.96E-05MD-2-related lipid recognition domain containing proteinSGN-U312452
651.370.000608triosephosphate isomerase, cytosolicSGN-U312988
681.360.004225unidentified
811.320.001128unidentified
82−1.310.00140833 kDa precursor protein of oxygen-evolving complexSGN-U312530
871.300.002306unidentified
89−1.30.000765unidentified
921.290.000125superoxide dismutaseSGN-U314405
981.280.000246triosephosphate isomerase, cytosolicSGN-U312988
Open in a separate window  相似文献   

13.
Expression,localization and interaction of SNARE proteins in Arabidopsis are selectively altered by the dark     
Naohiro Kato  Huancan Bai 《Plant signaling & behavior》2010,5(11):1470-1472
  相似文献   

14.
Genome-wide analysis of thioredoxin fold superfamily peroxiredoxins in Arabidopsis and rice     
Pavan Umate 《Plant signaling & behavior》2010,5(12):1543-1546
A broad range of peroxides generated in subcellular compartments, including chloroplasts, are detoxified with peroxidases called peroxiredoxins (Prx). The Prx are ubiquitously distributed in all organisms including bacteria, fungi, animals and also in cyanobacteria and plants. Recently, the Prx have emerged as new molecules in antioxidant defense in plants. Here, the members which belong to Prx gene family in Arabidopsis and rice are been identified. Overall, the Prx members constitute a small family with 10 and 11 genes in Arabidopsis and rice respectively. The prx genes from rice are assigned to their functional groups based on homology search against Arabidopsis protein database. Deciphering the Prx functions in rice will add novel information to the mechanism of antioxidant defense in plants. Further, the Prx also forms the part of redox signaling cascade. Here, the Prx gene family has been described for rice.Key words: antioxidant defense, chloroplast, gene family, oxidative stress, reactive oxygen speciesThe formation of free radicals and reactive oxygen species (ROS) occur in several enzymatic and non-enzymatic reactions during cellular metabolism. The accumulation of these reactive and deleterious intermediates is suppressed by antioxidant defense mechanism comprised of low molecular weight antioxidants and enzymes. In photosynthetic organisms, the defense against the damage from free radicals and oxidative stress is crucial. For instance, the ROS production occurs in photosystem II with generation of singlet oxygen (1O2) and hydrogen peroxide (H2O2),1,2 photosystem I from superoxide anion radicals (O2),3 and during photorespiration with generation of H2O2.4 ROS production may exceed under environmental stress conditions like excess light, low temperature and drought.5The antioxidant defense mechanism is activated by antioxidant metabolities and enzymes which detoxify ROS and lipid peroxides. The detoxification of ROS can occur in various cellular compartments such as chloroplasts, mitochondria, peroxisomes and cytosol.6 The enzymes like ascorbate peroxidase, catalase, glutathione peroxidase and superoxide dismutase are prominent antioxidant enzymes.6 The peroxiredoxins (Prx) emerged as new components in the antioxidant defense network of barley.7,8 Later, Prx were studied in other plants.914Prx can be classified into four different functional groups, PrxQ, 1-Cys Prx, 2-Cys Prx and Type-2 Prx.15,16 They are members of the thioredoxin fold superfamily.17,18 In this study, the prx genes found in Arabidopsis and rice genomes are been identified. The Arabidopsis genome encodes 10 prx genes classified into four functional categories, 1-Cys Prx, 2-Cys Prx, PrxQ and Type-2 Prx.13 Of these, one each of 1-Cys Prx and PrxQ, two of 2-Cys Prx (2-Cys PrxA and 2-Cys PrxB) and six Type-2 Prx (PrxA–F) are identified13 (LocusAnnotationSynonymA*B*C*AT1G481301-Cysteine peroxiredoxin 1 (ATPER1)1-Cys Prx21624081.36.603AT1G60740Peroxiredoxin type 2Type-2 PrxD16217471.95.2297AT1G65970Thioredoxin-dependent peroxidase 2 (TPX2)Type-2 PrxC16217413.95.2297AT1G65980Thioredoxin-dependent peroxidase 1 (TPX1)Type-2 PrxB16217427.84.9977AT1G65990Type 2 peroxiredoxin-relatedType-2 PrxA55362653.66.4368AT3G06050Peroxiredoxin IIF (PRXIIF)Type-2 PrxF20121445.29.3905AT3G116302-Cys Peroxiredoxin A (2CPA, 2-Cys PrxA)2-Cys PrxA26629091.77.5686AT3G26060ATPRX Q, periredoxin QPrxQ21623677.810.0565AT3G52960Peroxiredoxin type 2Type-2 PrxE23424684.09.572AT5G062902-Cysteine Peroxiredoxin B (2CPB, 2-Cys PrxB)2-Cys PrxB27329779.55.414Open in a separate window*A, amino acids; B, molecular weight; C, isoelectric point.In rice (rice.plantbiology.msu.edu/), there are 11 genomic loci which encode for Prx proteins (and33). Interestingly, a new prx gene (LOC_Os07g15670) annotated as “peroxiredoxin, putative, expressed” is identified making the tally of prx genes to eleven in rice as compared to ten in Arabidopsis (and22). The BLAST search has identified its counterpart in Arabidopsis which has been annotated as “antioxidant/oxidoreductase” (AT1G21350) in the TAIR database (www.arabidopsis.org). The rice LOC_Os07g15670 and Arabidopsis AT1G21350 share protein homology %68/78 for 236 amino acids (ChromosomeLocus IdPutative function/AnnotationA*B*C*1LOC_Os01g16152peroxiredoxin, putative, expressed19920873.68.22091LOC_Os01g24740peroxiredoxin-2E-1, chloroplast precursor, putative10711591.56.79061LOC_Os01g48420peroxiredoxin, putative, expressed16317290.85.68282LOC_Os02g09940peroxiredoxin, putative, expressed22623179.56.5352LOC_Os02g33450peroxiredoxin, putative, expressed26228096.95.77094LOC_Os04g339702-Cys peroxiredoxin BAS1, chloroplast precursor, putative, expressed12213410.24.37056LOC_Os06g09610peroxiredoxin, putative, expressed2662892610.50976LOC_Os06g42000peroxiredoxin, putative, expressed23323688.39.20597LOC_Os07g15670peroxiredoxin, putative, expressed25327684.69.85457LOC_Os07g44440peroxiredoxin, putative, expressed22124232.65.36187LOC_Os07g44430peroxiredoxin, putative25627785.36.8544Open in a separate window*A, amino acids; B, molecular weight; C, isoelectric point.

Table 3

Identification of rice homologs of peroxiredoxins in A. thaliana
Locus Id (Os*)Homolog (At*)NomenclatureIdentitity/Similarity (%)No. of aa* compared
LOC_Os01g16152AT3G06050Type-2 PrxF73/84201
LOC_Os01g24740AT1G65980Type-2 PrxB42/5977
LOC_Os01g48420AT1G65970Type-2 PrxC74/86162
LOC_Os02g09940AT1G60740Type-2 PrxD56/72166
LOC_Os02g33450AT5G062902-Cys Prx B74/82272
LOC_Os04g33970AT3G116302-Cys PrxA92/9688
LOC_Os06g09610AT3G26060PrxQ78/89159
LOC_Os06g42000AT3G52960Type-2 PrxE61/74240
LOC_Os07g15670AT1G21350Antioxidant68/78236
LOC_Os07g44440AT1G65990Type-2 PrxA27/4483
LOC_Os07g44430AT1G481301-Cys Prx69/83221
Open in a separate window*Os, Oryza sativa L.; At, Arabidopsis thaliana L.; aa, amino acids.The protein alignment study of Prx members in rice with the canonical Prx2-B and Prx2-E of Arabidopsis is shown in Figure 1. The Type-2 Prx proteins are characterized by the presence of catalytic cysteine (Cys) residues (Fig. 1). The alignment of rice Prx proteins shows that the Cys residue is well conserved in members like LOC_Os02g09940 (Type-2 PrxD), LOC_Os06g42000 (Type-2 Prx E), LOC_Os01g48420 (Type-2 Prx C), LOC_Os01g16152 (Type-2 Prx F), LOC_Os02g33450 (2-Cys Prx B), LOC_Os07g44440 (Type-2 Prx A), LOC_Os07g44430 (1-Cys Prx) and LOC_Os06g09610 (PrxQ) (Fig. 1). However, LOC_Os01g24740 (Type-2 PrxB) and LOC_Os04g33970 (2-Cys PrxA) which contain a chloroplast precursor do not have the catalytic Cys residues (Fig. 1). The newly identified LOC_Os07g15670 and AT1G21350 with annotations “peroxiredoxin, putative, expressed” and “antioxidant/oxidoreductase” respectively do not have catalytic Cys residues as well (Fig. 1).Open in a separate windowFigure 1Amino acid alignment of peroxiredoxins (Prx) in rice. The rice proteins are aligned with the canonical Arabidopsis Prx2-B and Prx2-E. The conserved cysteine residues are indicated by arrows on top of the alignment. Note the sequence conservation between the newly identified LOC_Os07g15670 and AT1G21350. The rice locus Ids are identified on left and amino acid positions on right. The alignment was made with ClustalX.Taken together, the results demonstrate that like Arabidopsis, the Prx constitute a small gene family in rice. However, the functional role of Prx in rice is not clearly understood.  相似文献   

15.
Are loline alkaloid levels regulated in grass endophytes by gene expression or substrate availability?     
Dong-Xiu Zhang  Padmaja Nagabhyru  Jimmy D Blankenship  Christopher L Schardl 《Plant signaling & behavior》2010,5(11):1419-1422
  相似文献   

16.
Sources of floral scent variation: Can environment define floral scent phenotype?     
Cassie J Majetic  Robert A Raguso  Tia-Lynn Ashman 《Plant signaling & behavior》2009,4(2):129-131
Studies of floral scent generally assume that genetic adaptation due to pollinator-mediated natural selection explains a significant amount of phenotypic variance, ignoring the potential for phenotypic plasticity in this trait. In this paper, we assess this latter possibility, looking first at previous studies of floral scent variation in relation to abiotic environmental factors. We then present data from our own research that suggests among-population floral scent variation is determined, in part, by environmental conditions and thus displays phenotypic plasticity. Such an outcome has strong ramifications for the study of floral scent variation; we conclude by presenting some fundamental questions that should lead to greater insight into our understanding of the evolution of this trait, which is important to plant-animal interactions.Key words: abiotic factors, aromatics, floral scent, GxE interaction, phenotypic plasticity, pollination, terpenoids, volatilesFloral scent is thought to function as a major non-visual attractive cue for many pollinators in a large number of plant systems1,2 and therefore most research on this plant trait has proceeded in the context of pollination ecology. Such studies have revealed the physiological and behavioral responses of pollinators to various floral volatiles (reviewed in refs. 3 and 4), convergent evolution of odor phenotypes attractive to specific pollinator classes (reviewed in refs. 5 and 6), reproductive isolation of plant species due to differences in pollinator attraction by scent,7 and instances of deception in which flowers mimic insect pheromones to effect pollination.8 Together, this body of evidence suggests that specific floral scent profiles can have important implications for the reproductive potential of many plant species.This pollinator-centered viewpoint has carried through to research on floral scent variation, including our most recent work on the insect-pollinated species Hesperis matronalis (Brassicaceae).9 Such studies usually suggest that the floral scent variation commonly found within and among individuals, populations and species (reviewed in ref. 2) is due to genetic differentiation as a result of selection by pollinators over time (reviewed in ref. 10). But an organism''s genes are only one factor determining phenotype. Both biotic (living) and abiotic (non-living) environmental conditions can profoundly affect phenotype expression, leading to significant variation. For plants, abiotic factors such as climate and soil chemistry can have particularly strong effects on phenotypes. When these environmental conditions cause changes in phenotype, we would say that a trait displays phenotypic plasticity.1113 A number of studies have uncovered phenotypic plasticity for many different plant traits.12 However, while phenotypic variation in floral scent has been well-documented1,2 and correlated with variation in biotic factors like pollinator behavior,1417 these studies were decidedly focused on natural selection, rather than phenotypic plasticity, as an organizational framework.However, in examining the scientific literature on floral scent, we found four studies in which the effects of naturally variable abiotic factors on floral scent profiles were examined, three of which were performed by the same research group (1821 (21). Moreover, these studies are decidedly not analyzed and interpreted using standard protocols for phenotypic plasticity studies.13

Table 1

A survey of previous studies examining changes in floral scent phenotype due to abiotic factors
StudySpeciesEnvironmental characteristicPlant materialStudy locationChange in volatile emissions?Direction of change
Loper and Berdel 1978Medicago sativa L.IrrigationClonesExperimental farmNon/a
CuttingClonesExperimental farmNon/a
Hansted et al. 1994Ribes nigrumTemperatureTwo varietiesGrowth chamberYes+ temperature, + ER*
Jakobsen and Olsen 1994Trifolium repens L.TemperatureCultivarGrowth chamberYes+ temperature, + ER
IrradianceCultivarGrowth chamberYes+ irradiance, + ER
Air HumidityCultivarGrowth chamberYes+ humidity, − ER
Nielsen et al. 1995Hesperis matronalis L.TemperatureWild seedsGrowth chamberYes+ temperature,
+ monoterpene ER
This study, 2009Hesperis matronalisGrowingWild plantsWild vs.YesWild—different ER,
EnvironmentCommon GardenSC between populations;
Garden—similar ER,
SC between populations
Open in a separate window*Plus signs indicate a numerical increase, minus signs indicate a decrease; ER = floral scent emission rate, SC = scent composition.Research we have conducted in conjunction with our recently published work on the floral scent of H. matronalis9 suggests that some of the natural variation in the odor of this species may be attributable to phenotypic plasticity. We reared potted H. matronalis rosettes from two populations (PA1 and PA2) in northwestern Pennsylvania in a common garden environment and upon flowering, collected scent from these individuals using dynamic headspace extractions (reviewed in ref. 9). We then compared floral scent composition and emission rates of potted plants with each other (between populations in a common garden), as well as with the floral scent profiles of plants reared in their source population (i.e., between individuals from the same population reared in different environments). The results were striking. Analysis of scent composition using non-metric multidimensional scaling and analysis of similarity (NMDS and ANOSIM, respectively: reviewed in ref. 9) suggested that the scent composition of plant populations reared in their native environments differ significantly from each other in terms of two major biosynthetic classes of volatiles—aromatics and terpenoids (Fig. 1, filled symbols only). This was especially true for the aromatic eugenol and derivatives of the terpenoid linalool (furanoid linalool oxides and linalool epoxide). In contrast, common-garden reared plants from different populations did not differ in floral scent composition, regardless of their original source population. Perhaps even more interestingly, while both populations showed changes due to rearing environment, the degree of change differed: in only one population (PA1) did scent composition change significantly between native and garden reared plants (Fig. 1).Open in a separate windowFigure 1NMDS (non-metric multidimensional scaling) plots of scent composition for purple morphs from two populations of Hesperis matronalis—(A) Aromatics and (B) Terpenoids. Filled symbols represent scent from home environment in situ plants, which are significantly different from one another as determined by analysis of similarity (ANOSIM: aromatics—p = 0.03, R = 0.22; terpenoids—p = 0.01, R = 0.25). Open symbols represent scent from plants reared in a common environment. Population PA1 is represented by triangles and population PA2 is represented by squares. Arrows indicate the direction of shift from home environment to common garden floral scent composition; black arrows represent a significant difference between groups determined by ANOSIM (Aromatics—p = 0.01, R = 0.30; Terpenoids—p = 0.06; R = 0.20) and gray arrows represent a non-significant difference.Floral scent emission rate also showed environmentally induced differences. While wild plants from our two populations differed significantly in the amount of scent emitted in situ, with PA1 emitting more total scent, total aromatics and total terpenoids,9 we found that rearing plants from these sites in a common garden environment either significantly reverses the direction of differences in emission rates seen between natural populations, with PA2 now emitting more aromatic scent (Analysis of Variance: F = 4.09; p = 0.05; Fig. 2A), or homogenizes the quantity of scent emitted (i.e., no significant differences in emission rates between populations; Fig. 2B and C).Open in a separate windowFigure 2Box plots of scent emission rates for purple Hesperis matronalis plants grown in common garden environments in terms of (A) Aromatics, (B) Terpenoids and (C) Total Scent. The edges of each box represent the range of data between the 25th percentile and the 75th percentile, while the horizontal bar indicates the median for each population. The error bars on each box extend to the 5th and 95th percentile of the data range respectively. To the right of each box plot, the mean is presented as a horizontal line, with standard error bars. Mean values not sharing letters are significantly different as determined by analysis of variance (ANOVA).Together, these results suggest that rearing environment can have a profound effect on floral scent composition and emission rate, such that plants from the same maternal environment can have radically different floral scent phenotypes in response to differential growing conditions. If our work effectively incorporates a random genetic sample from each population into each growing environment, then at least some of the phenotypic variation we describe here could be interpreted as phenotypic plasticity. This experiment does not allow us to pinpoint the exact environmental conditions associated with phenotypic differences in floral scent (although variation in nutrient or water availability between wild and common-garden settings is likely), nor does it completely conform to the traditional “reactionnorm” studies associated with plasticity research which would allow detection of genetic variation in scent plastiticy.12,13 However, our results suggest that floral scent of plants grown in wild populations may be plastic, which provides some additional insight into our recently published work uncovering significant among-population variation in floral scent.9 For researchers that study phenotypic plasticity, such an outcome is probably not a surprise, nor is our finding that populations respond differently to environmental conditions (i.e., potential GxE interaction, reflecting genetic variability in plasticity).However, if floral scent can be plastic, this raises a number of biologically relevant questions that should be addressed in floral scent research, including: (1) Is there truly a canonical floral scent blend that can be attributed to a given plant species, as is normally supposed by those studying floral scent from an evolutionary perspective? (2) Which environmental conditions exert the strongest influence on floral scent profiles in a species? (3) How do such conditions interact with genetic variation in the factors responsible for scent biosynthesis and emission? (4) Are floral scent profiles plastic within a single flowering period; if so, what impact does this have on pollinator behavior and therefore plant fitness? (5) At what scale do biotic agents such as pollinators and herbivores respond to quantitative and qualitative variation in floral scent? Studies that address these questions should lead us to a more mature understanding of the causes and consequences of natural variation in floral scent.  相似文献   

17.
Natural Infection of Burkholderia pseudomallei in an Imported Pigtail Macaque (Macaca nemestrina) and Management of the Exposed Colony     
Crystal H Johnson  Brianna L Skinner  Sharon M Dietz  David Blaney  Robyn M Engel  George W Lathrop  Alex R Hoffmaster  Jay E Gee  Mindy G Elrod  Nathaniel Powell  Henry Walke 《Comparative medicine》2013,63(6):528-535
Identification of the select agent Burkholderia pseudomallei in macaques imported into the United States is rare. A purpose-bred, 4.5-y-old pigtail macaque (Macaca nemestrina) imported from Southeast Asia was received from a commercial vendor at our facility in March 2012. After the initial acclimation period of 5 to 7 d, physical examination of the macaque revealed a subcutaneous abscess that surrounded the right stifle joint. The wound was treated and resolved over 3 mo. In August 2012, 2 mo after the stifle joint wound resolved, the macaque exhibited neurologic clinical signs. Postmortem microbiologic analysis revealed that the macaque was infected with B. pseudomallei. This case report describes the clinical evaluation of a B. pseudomallei-infected macaque, management and care of the potentially exposed colony of animals, and protocols established for the animal care staff that worked with the infected macaque and potentially exposed colony. This article also provides relevant information on addressing matters related to regulatory issues and risk management of potentially exposed animals and animal care staff.Abbreviations: CDC, Centers for Disease Control and Prevention; IHA, indirect hemagglutination assay; PEP, postexposure prophylacticBurkholderia pseudomallei, formerly known as Pseudomonas pseudomallei, is a gram-negative, aerobic, bipolar, motile, rod-shaped bacterium. B. pseudomallei infections (melioidosis) can be severe and even fatal in both humans and animals. This environmental saprophyte is endemic to Southeast Asia and northern Australia, but it has also been found in other tropical and subtropical areas of the world.7,22,32,42 The bacterium is usually found in soil and water in endemic areas and is transmitted to humans and animals primarily through percutaneous inoculation, ingestion, or inhalation of a contaminated source.8, 22,28,32,42 Human-to-human, animal-to-animal, and animal-to-human spread are rare.8,32 In December 2012, the National Select Agent Registry designated B. pseudomallei as a Tier 1 overlap select agent.39 Organisms classified as Tier 1 agents present the highest risk of deliberate misuse, with the most significant potential for mass casualties or devastating effects to the economy, critical infrastructure, or public confidence. Select agents with this status have the potential to pose a severe threat to human and animal health or safety or the ability to be used as a biologic weapon.39Melioidosis in humans can be challenging to diagnose and treat because the organism can remain latent for years and is resistant to many antibiotics.12,37,41 B. pseudomallei can survive in phagocytic cells, a phenomenon that may be associated with latent infections.19,38 The incubation period in naturally infected animals ranges from 1 d to many years, but symptoms typically appear 2 to 4 wk after exposure.13,17,35,38 Disease generally presents in 1 of 2 forms: localized infection or septicemia.22 Multiple methods are used to diagnose melioidosis, including immunofluorescence, serology, and PCR analysis, but isolation of the bacteria from blood, urine, sputum, throat swabs, abscesses, skin, or tissue lesions remains the ‘gold standard.’9,22,40,42 The prognosis varies based on presentation, time to diagnosis, initiation of appropriate antimicrobial treatment, and underlying comorbidities.7,28,42 Currently, there is no licensed vaccine to prevent melioidosis.There are several published reports of naturally occurring melioidosis in a variety of nonhuman primates (NHP; 2,10,13,17,25,30,31,35 The first reported case of melioidosis in monkeys was recorded in 1932, and the first published case in a macaque species was in 1966.30 In the United States, there have only been 7 documented cases of NHP with B. pseudomallei infection.2,13,17 All of these cases occurred prior to the classification of B. pseudomallei as a select agent. Clinical signs in NHP range from subclinical or subacute illness to acute septicemia, localized infection, and chronic infection. NHP with melioidosis can be asymptomatic or exhibit clinical signs such as anorexia, wasting, purulent drainage, subcutaneous abscesses, and other soft tissue lesions. Lymphadenitis, lameness, osteomyelitis, paralysis and other CNS signs have also been reported.2,7,10,22,28,32 In comparison, human''s clinical signs range from abscesses, skin ulceration, fever, headache, joint pain, and muscle tenderness to abdominal pain, anorexia, respiratory distress, seizures, and septicemia.7,9,21,22

Table 1.

Summary of reported cases of naturally occurring Burkholderia pseudomalleiinfections in nonhuman primates
CountryaImported fromDate reportedSpeciesReference
AustraliaBorneo1963Pongo sp.36
BruneiUnknown1982Orangutan (Pongo pygmaeus)33
France1976Hamlyn monkey (Cercopithecus hamlyni) Patas monkey (Erythrocebus patas)11
Great BritainPhilippines and Indonesia1992Cynomolgus monkey (Macaca fascicularis)10
38
MalaysiaUnknown1966Macaca spp.30
Unknown1968Spider monkey (Brachytelis arachnoides) Lar gibbon (Hylobates lar)20
Unknown1969Pig-tailed macaque (Macaca nemestrina)35
Unknown1984Banded leaf monkey (Presbytis melalophos)25
SingaporeUnknown1995Gorillas, gibbon, mandrill, chimpanzee43
ThailandUnknown2012Monkey19
United StatesThailand1970Stump-tailed macaque (Macaca arctoides)17
IndiaPig-tailed macaque (Macaca nemestrina)
AfricaRhesus macaque (Macaca mulatta) Chimpanzee (Pan troglodytes)
Unknown1971Chimpanzee (Pan troglodytes)3
Malaysia1981Pig-tailed macaque (Macaca nemestrina)2
Wild-caught, unknown1986Rhesus macaque (Macaca mulatta)13
Indonesia2013Pig-tailed macaque (Macaca nemestrina)Current article
Open in a separate windowaCountry reflects the location where the animal was housed at the time of diagosis.Here we describe a case of melioidosis diagnosed in a pigtail macaque (Macaca nemestrina) imported into the United States from Indonesia and the implications of the detection of a select agent identified in a laboratory research colony. We also discuss the management and care of the exposed colony, zoonotic concerns regarding the animal care staff that worked with the shipment of macaques, effects on research studies, and the procedures involved in reporting a select agent incident.  相似文献   

18.
Snail: More than EMT     
Yadi Wu  Binhua P. Zhou 《Cell Adhesion & Migration》2010,4(2):199-203
  相似文献   

19.
Prion interference with multiple prion isolates     
Charles R Schutt  Jason C Bartz 《朊病毒》2008,2(2):61-63
Co-inoculation of prion strains into the same host can result in interference, where replication of one strain hinders the ability of another strain to cause disease. The drowsy (DY) strain of hamster-adapted transmissible mink encephalopathy (TME) extends the incubation period or completely blocks the hyper (HY) strain of TME following intracerebral, intraperitoneal or sciatic nerve routes of inoculation. However, it is not known if the interfering effect of the DY TME agent is exclusive to the HY TME agent by these experimental routes of infection. To address this issue, we show that the DY TME agent can block hamster-adapted chronic wasting disease (HaCWD) and the 263K scrapie agent from causing disease following sciatic nerve inoculation. Additionally, per os inoculation of DY TME agent slightly extends the incubation period of per os superinfected HY TME agent. These studies suggest that prion strain interference can occur by a natural route of infection and may be a more generalized phenomenon of prion strains.Key words: prion diseases, prion interference, prion strainsPrion diseases are fatal neurodegenerative diseases that are caused by an abnormal isoform of the prion protein, PrPSc.1 Prion strains are hypothesized to be encoded by strain-specific conformations of PrPSc resulting in strain-specific differences in clinical signs, incubation periods and neuropathology.27 However, a universally agreed upon definition of prion strains does not exist. Interspecies transmission and adaptation of prions to a new host species leads to the emergence of a dominant prion strain, which can be due to selection of strains from a mixture present in the inoculum, or produced upon interspecies transmission.8,9 Prion strains, when present in the same host, can interfere with each other.Prion interference was first described in mice where a long incubation period strain 22C extended the incubation period of a short incubation period strain 22A following intracerebral inoculation.10 Interference between other prion strains has been described in mice and hamsters using rodent-adapted strains of scrapie, TME, Creutzfeldt-Jacob disease and Gerstmannn-Sträussler-Scheinker syndrome following intracerebral, intraperitoneal, intravenous and sciatic nerve routes of inoculation.1015 We previously demonstrated the detection of PrPSc from the long incubation period DY TME agent correlated with its ability to extend the incubation period or completely block the superinfecting short incubation period HY TME agent from causing disease and results in a reduction of HY PrPSc levels following sciatic nerve inoculation.12 However, it is not known if a single long incubation period agent (e.g., DY TME) can interfere with more than one short incubation period agent or if interference can occur by a natural route of infection.To examine the question if one long incubation period agent can extend the incubation period of additional short incubation period agents, hamsters were first inoculated in the sciatic nerve with the DY TME agent 120 days prior to superinfection with the short-incubation period agents HY TME, 263K scrapie and HaCWD.1618 The HY TME and 263K scrapie agents have been biologically cloned and have distinct PrPSc properties.19,20 The HaCWD agent used in this study is seventh hamster passage that has not been biologically cloned and therefore will be referred to as a prion isolate. Sciatic nerve inoculations were performed as previously described.11,12 Briefly, hamsters were inoculated with 103.0 i.c. LD50 of the DY TME agent or equal volume (2 µl of a 1% w/v brain homogenate) of uninfected brain homogenate 120 days prior to superinfection of the same sciatic nerve with either 104.6 i.c. LD50 of the HY TME agent, 105.2 i.c. LD50 of the HaCWD agent or 104.6 i.c. LD50/g 263K scrapie agent (Bartz J, unpublished data).16,18,21 Animals were observed three times per week for the onset of clinical signs of HY TME, 263K and HaCWD based on the presence of ataxia and hyperexcitability, while the clinical diagnosis of DY TME was based on the appearance of progressive lethargy.1618 The incubation period was calculated as the number of days between the onset of clinical signs of the agent strain that caused disease and the inoculation of that strain. The Student''s t-test was used to compare incubation periods.12 We found that sciatic nerve inoculation of both the HaCWD agent and 263K scrapie agent caused disease with a similar incubation period to animals infected with the HY TME agent (12 In hamsters inoculated with the DY TME agent 120 days prior to superinfection with the HaCWD or 263K agents, the animals developed clinical signs of DY TME with an incubation period that was not different from the DY TME agent control group (12 The PrPSc migration properties were consistent with the clinical diagnosis and all co-infected animals had PrPSc that migrated similar to PrPSc from the DY TME agent infected control animal (Fig. 1, lanes 1–10). This data indicates that the DY TME agent can interfere with more than one isolate and that interference in the CNS may be a more generalized phenomenon of prion strains.Open in a separate windowFigure 1The strain-specific properties of PrPSc correspond to the clinical diagnosis of disease. Western blot analysis of 250 µg brain equivalents of proteinase K digested brain homogenate from prion-infected hamsters following intracerebral (i.c.), sciatic nerve (i.sc.) or per os inoculation with either the HY TME (HY), DY TME (DY), 263K scrapie (263K), hamster-adapted CWD (CWD) agents or mock-infected (UN). The unglycoyslated PrPSc glycoform of HY TME, 263K scrapie and hamster-adapted CWD migrates at 21 kDa. The unglycosylated PrPSc glycoform of DY PrPSc migrates at 19 kDa. Migration of 19 and 21 kDa PrPSc are indicated by the arrows on the left of the figure. n.a., not applicable.

Table 1

Clinical signs and incubation periods of hamsters inoculated in the sciatic nerve with either the HY TME, HaCWD or 263K scrapie agents, or co-infected with the DY TME agent 120 days prior to superinfection of hamsters with the HY TME, HaCWD or 263K agents
Onset of clinical signs
First inoculationInterval between inoculationsSecond inoculationClinical signsPrP-res migrationA/IaAfter 1st inoculationAfter 2nd inoculation
Mock120 daysHY TMEHY TME21 kDa5/5n.a.72 ± 3b
Mock120 daysHaCWDHaCWD21 kDa5/5n.a.73 ± 3
Mock120 days263K263K21 kDa5/5n.a.72 ± 3
DY TME120 daysMockDY TME19 kDa4/4224 ± 2n.a.
DY TME120 daysHY TMEDY TME19 kDa5/5222 ± 2c102 ± 2
DY TME120 daysHaCWDDY TME19 kDa5/5223 ± 3c103 ± 3
DY TME120 days263KDY TME19 kDa5/5222 ± 2c102 ± 2
Open in a separate windowaNumber affected/number inoculated;bAverage days postinfection ± standard deviation;cIncubation period similar compared to control animals inoculated with the DY TME agent alone (p > 0.05). n.a., not applicable.To examine the question if prion interference can occur following a natural route of infection, hamsters were first inoculated per os with the DY TME agent and then superinfected per os with the HY TME agent at various time points post DY TME agent infection. Hamsters were per os inoculated by drying the inoculum on a food pellet and feeding this pellet to an individual animal as described previously.22 For the per os interference experiment, 105.7 i.c. LD50 of the DY TME agent or an equal volume of uninfected brain homogenate (100 µl of a 10% w/v brain homogenate) was inoculated 60, 90 or 120 days prior to per os superinfection of hamsters with 107.3 i.c. LD50 of the HY TME agent. A 60 or 90 day interval between DY TME agent infection and HY TME agent superinfection resulted in all of the animals developing clinical signs of HY TME with incubation periods that are similar to control hamsters inoculated with the HY TME agent alone (Fig. 1, lanes 11–16). The eight-day extension in the incubation period of HY TME in the 120 day interval co-infected group is consistent with a 1 log reduction in titer.21 This is the first report of prion interference by the per os route of infection, a likely route of prion infection in natural prion disease and provides further evidence that prion strain interference could occur in natural prion disease.2325

Table 2

Clinical signs and incubation periods of hamsters per os inoculated with either the HY TME or DY TME agent, or per os co-infected with the DY TME agent 60, 90 or 120 days prior to superinfection of hamsters with the HY TME agent
Onset of clinical signs
First inoculationInterval between inoculationsSecond inoculationClinical signsPrP-res migrationA/IaAfter 1st inoculationAfter 2nd inoculation
Mock120 daysHY TMEHY TME21 kDa5/5n.a.140 ± 5b
DY TME60 daysHY TMEHY TME21 kDa5/5195 ± 6135 ± 6
DY TME90 daysHY TMEHY TME21 kDa5/5230 ± 5140 ± 5
DY TME120 daysHY TMEHY TME21 kDa5/5269 ± 3149 ± 3c
Open in a separate windowaNumber affected/number inoculated;bAverage days postinfection ± standard deviation;cIncubation period extended compared to control animals inoculated with the HY TME agent alone (p < 0.01); n.a., not applicable.The capacity of the DY TME agent to replicate modulates its ability to interfere with the HY TME agent. TME interference, following sciatic nerve inoculation, occurs in the lumbar spinal cord and DY PrPSc abundance in this structure correlates with the ability of the DY TME agent to interfere with the HY TME agent.12 Following extraneural routes of infection, DY TME agent replication and PrPSc deposition are not detected in spleen or lymph nodes, which is the major site of extraneural HY TME agent replication.11,21,26 The DY TME agent can interfere with the HY TME agent following intraperitoneal and per os infection, suggesting that the DY TME agent is replicating in other locations that are involved in HY TME agent neuroinvasion (11  相似文献   

20.
Transcriptional and Functional Classification of the GOLVEN/ROOT GROWTH FACTOR/CLE-Like Signaling Peptides Reveals Their Role in Lateral Root and Hair Formation     
Ana Fernandez  Andrzej Drozdzecki  Kurt Hoogewijs  Anh Nguyen  Tom Beeckman  Annemieke Madder  Pierre Hilson 《Plant physiology》2013,161(2):954-970
  相似文献   

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