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1.
Recombination of strain O segments to HCpro‐encoding sequence of strain N of Potato virus Y modulates necrosis induced in tobacco and in potatoes carrying resistance genes Ny or Nc
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Hypersensitive resistance (HR) to strains O and C of Potato virus Y (PVY, genus Potyvirus) is conferred by potato genes Nytbr and Nctbr, respectively; however, PVY N strains overcome these resistance genes. The viral helper component proteinases (HCpro, 456 amino acids) from PVYN and PVYO are distinguished by an eight‐amino‐acid signature sequence, causing HCpro to fold into alternative conformations. Substitution of only two residues (K269R and R270K) of the eight‐amino‐acid signature in PVYN HCpro was needed to convert the three‐dimensional (3D) model of PVYN HCpro to a PVYO‐like conformation and render PVYN avirulent in the presence of Nytbr, whereas four amino acid substitutions were necessary to change PVYO HCpro to a PVYN‐like conformation. Hence, the HCpro conformation rather than other features ascribed to the sequence were essential for recognition by Nytbr. The 3D model of PVYC HCpro closely resembled PVYO, but differed from PVYN HCpro. HCpro of all strains was structurally similar to β‐catenin. Sixteen PVYN605‐based chimeras were inoculated to potato cv. Pentland Crown (Nytbr), King Edward (Nctbr) and Pentland Ivory (Nytbr/Nctbr). Eleven chimeras induced necrotic local lesions and caused no systemic infection, and thus differed from both parental viruses that infected King Edward systemically, and from PVYN605 that infected Pentland Crown and Pentland Ivory systemically. These 11 chimeras triggered both Nytbr and Nctbr and, in addition, six induced veinal necrosis in tobacco. Further, specific amino acid residues were found to have an additive impact on necrosis. These results shed new light on the causes of PVY‐related necrotic symptoms in potato. 相似文献
2.
After SO2 fumigation, Quercus acutissima and Pinus densiflora maintained high net photosynthetic rate (P
N) and did not show visible symptoms of damage. In contrast, Populus alba×glandulosa and Acanthopanax sessiliflorus had significantly reduced P
N and showed visible necrosis.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
The results of the first detailed screening of a resistance to Bremia lactucae in naturally growing populations of Lactuca saligna are presented here. In total, 146 accessions from 25 populations of L. saligna originating in Israel (N = 136), France (N = 8), Jordan (N = 1) and Turkey (N = 1) were tested at seedling stage for their resistance to 10 highly virulent isolates (races) of B. lactucae from Lactuca sativa (DEG2, Bl:5, Bl:15, Bl:16, Bl:17, Bl:18, Bl:21, Bl:22, Bl:24 and Bl:25). Our study strongly supports the suggestion that L. saligna is indeed generally highly resistant to B. lactucae. However, our results provide evidence that at least at a seedling stage L. saligna may not be a non‐host plant for B. lactucae, as was hypothesised for approximately the last 30 years. Some accessions expressed a differential (i.e. race‐specific) response, which accords with other recently published data for this Lactuca species. Furthermore, some geographical differences in race‐specific resistance were observed, too. Tests performed at an adult‐plant stage, however, did not prove race‐specificity of the respective accessions. To summarise, what is behind the race‐specific character of the responses observed at a seedling stage is still uncertain, as is its comparability with the race‐specific resistance of some other Lactuca species such as L. sativa or L. serriola. The presence of plant stage‐dependent resistance, governed by a combined effect of different quantitative trait loci in young and adult plants of L. saligna, is discussed. 相似文献
4.
Thirty-nine Brassica coenospecies grown in pot cultures during 1993 and 1994 were screened for variability in photosynthetic rate (P
N
) and leaf characters. There were significant differences among the species in P
N
per unit leaf area, chlorophyll (Chl) content, specific leaf mass (SLM), stomatal resistance (r
s
) and individual leaf size. The interactions species x year and species x date of measurement were small compared to the species
effect. There was a significant negative correlation between P
N
and r
s
and a
significant positive one between P
N
and both Chl content and SLM.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Mengjie Liu Ya-Jie Li Yu-Xiu Zhu Yang Sun Guan-Feng Wang 《Molecular Plant Pathology》2021,22(5):564-579
Most plant intracellular immune receptors belong to nucleotide-binding, leucine-rich repeat (NLR) proteins. The recognition between NLRs and their corresponding pathogen effectors often triggers a hypersensitive response (HR) at the pathogen infection sites. The nicotinate N-methyltransferase (NANMT) is responsible for the conversion of nicotinate to trigonelline in plants. However, the role of NANMT in plant defence response is unknown. In this study, we demonstrated that the maize ZmNANMT, but not its close homolog ZmCOMT, an enzyme in the lignin biosynthesis pathway, suppresses the HR mediated by the autoactive NLR protein Rp1-D21 and its N-terminal coiled-coil signalling domain (CCD21). ZmNANMT, but not ZmCOMT, interacts with CCD21, and they form a complex with HCT1806 and CCoAOMT2, two key enzymes in lignin biosynthesis, which can also suppress the autoactive HR mediated by Rp1-D21. ZmNANMT is mainly localized in the cytoplasm and nucleus, and either localization is important for suppressing the HR phenotype. These results lay the foundation for further elucidating the molecular mechanism of NANMTs in plant disease resistance. 相似文献
6.
Antonella Pannocchia Silvia Revelli Giacomo Tamponi Angelica Giorgianni Roberta Todde Amalia Bosia Dario Ghigo 《Cell biochemistry and function》1996,14(1):11-18
Although multidrug resistance (mdr) may arise through a variety of mechanisms, the most widely studied and accepted form is associated with an increased concentration of P-glycoprotein (P-gp), a 170kd protein found in the membrane fraction of a number of mammalian cells. Since mdr seems to be related to the ability of resistant cells to extrude drugs and the circumvention of mdr is supposed to be due to the restored ability to accumulate drugs, membrane has been regarded as the crucial site for such a regulation and an important role for membrane ion exchangers has been suggested. The aim of this work was to elucidate whether the Na+/H+ antiporter is involved in the mechanism of regulation and circumvention of mdr and if 5-(N-ethyl-N-isopropyl) amiloride (EIPA), a selective inhibitor of the Na+/H+ exchanger, can modulate the functional expression of the mdr phenotype. The effect of EIPA on doxorubicin (DX) resistant cells (LoVo/DX) obtained from a human colon adenocarcinoma cell line (LoVo) was studied. EIPA at concentrations ranging from 10 to 50 μM was able to increase the antibiotic cytotoxicity in the resistant Lovo/DX cells. The reversal of DX resistance paralleled an increase of the ability of the cells to accumulate the drug. Both drug loading and sensitivity to the inhibitory effect of DX on cell proliferation were restored by EIPA in a dose-dependent way. These results suggest a new mechanism of mdr reversal and indicate that amiloride and its derivatives may be useful in reversing DX resistance and in enhancing the clinical effectiveness of chemotherapeutics. 相似文献
7.
Xiaoke Gu Mingyu Guan Chunyu Jiang Qinghua Song Xin Li Nan Sun Jing Chen Jingying Qiu 《化学与生物多样性》2021,18(2):e2000775
P-Glycoprotein (P-gp) overexpression is considered to be the leading cause of multidrug resistance (MDR) and failure of chemotherapy for leukemia. In this study, seventeen thiosemicarbazone-containing compounds were prepared and evaluated as potential antileukemia agents against drug resistant K562/A02 cell overexpressing P-gp. Among them, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide could significantly inhibit K562/A02 cells proliferation with an IC50 value of 0.96 μM. Interestingly, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide could dose-dependently increase ROS levels of drug resistant K562/A02 cells, thus displaying a potential collateral sensitivity (CS)-inducing effect and selectively killing K562/A02 cells. Furthermore, N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide possessed potent inhibitory effect on HDAC1 and HDAC6, and could promote K562/A02 cells apoptosis via dose-dependently increasing Bax expression, reducing Bcl-2 protein level, and inducing the cleavage of PARP and caspase3. These present findings suggest that N-hydroxy-6-({(2E)-2-[(3-nitrophenyl)methylidene]hydrazinecarbothioyl}amino)hexanamide might be a promising lead to discover novel antileukemia agents against P-gp overexpressing leukemic cells. 相似文献
8.
L. Garcia‐Gonzalez A. Rajkovic A.H. Geeraerd K. Elst L. Van Ginneken J.F. Van Impe F. Devlieghere 《Letters in applied microbiology》2010,50(6):653-656
Aims: The objective of this study was to investigate whether bacterial cells could develop resistance (as a part of their adaptation strategy) to high‐pressure CO2 (HPCD) inactivation. Methods and Results: Alternating cycles of exposure to pressurized CO2 (10·5 MPa, 35°C, 400 min?1, 70% working volume ratio during 10 min) and re‐growth of the surviving subpopulation were used to investigate possible increases in the resistance of Escherichia coli and Listeria monocytogenes to HPCD. The results show an increased resistance of both pathogens tested after seven cycles of inactivation. Increase in the resistance after 15 cycles resulted in a difference of 2·4 log CFU ml?1 in log N0/Ni when parental (N0) and treated cultures (Ni) of E. coli and L. monocytogenes were compared. Conclusions: Current findings indicate the ability of micro‐organisms to adapt to HPCD preservation technology. Significance and Impact of the Study: The occurrence of HPCD‐resistant micro‐organisms could pose a new hazard to the safety and stability of HPCD‐processed foods. 相似文献
9.
J P T VALKONEN 《The Annals of applied biology》1997,130(1):91-104
Novel potyvirus resistance specificities were found in eight tested wild potato species (clones): hypersensitive resistance (HR) to potato Y potyvirus (PVY) strain groups PVYO in Solanum megistacrolobum and S. polyadenium and PVYN in S. stoloniferum; HR to potato V potyvirus (PW) in S. maglia, S. polyadenium, S. stoloniferum, S. sparsipilum and S. sucrense, HR to potato A potyvirus (PVA) strain group 1 in S. sucrense, and extreme resistance (ER) to PVA in S. polyadenium. S. commersonii and S. stoloniferum expressed HR to tobacco etch potyvirus (TEV) which has not been reported previously in potato species. The studied clone of S. stoloniferum expressed HR to all potyviruses and potyvirus strains tested. The clone of S. stoloniferum (2n = 48; nuclear DNA content (2C) = 3.6 pg) and S. chacoense (2n = 24; 2C=1.9 pg) were crossed and one hybrid (2n = 36; 2C = 2.9 pg) was obtained. The hybrid expressed HR to all tested potyviruses except PVA, which indicated that HR to PVA was controlled by a gene which is different from the genes (or gene) controlling HR to PVYO, PVYN, PVV and TEV in S. stoloniferum. On the other hand, S. chacoense and the hybrid expressed ER to cucumber mosaic cucumovirus (CMV), whereas S. stoloniferum was susceptible to CMV. All tested wild species and the six tested potato cultivars (S. tuberosum subsp. tuberosum) expressed HR to PVV. Expression of HR following infection with PVYN induced systemic acquired resistance (SAR) in S. chacoense. HR to PVYN in S. sparsipilum and S. sucrense and to PVYO in potato cv. Pito was efficiently expressed at lower temperatures (16/18°C) indicated by the development of distinct necrotic lesions and/or vein necrosis in inoculated leaves, whereas the HR was rendered less effective at higher temperatures (19/24°C) which was indicated by the development of systemic infection with leaf-drop and mosaic symptoms. 相似文献
10.
A total of 59 Solanum tuberosum androgenetic plants have been obtained through anther culture, 47 of which derived from a tetraploid clone, seven from a
diploid hybrid, and five from an anther-derived clone. About two thirds of the anther-derived plants were dihaploids, a few
were monohaploids (5.08%) or aneuploids (6.78%), whereas the tetraploid genotype generated about a third of tetraploids. Seven
hundred twenty seven R1 plants arisen from tubers of the androgenetic potatoes were mechanically inoculated with the necrotic strain of the potato
Y potyvirus (PVYN) and grown in a glasshouse. Fifty days after inoculation, the presence of PVYN in R1 plants was detected by DAS-ELISA (Double Autibody Sandwich). Only three plants (0.4%) of genotype H2-258 exhibited local
necrotic symptoms (hypersensitivity reaction) suggesting the presence of the N
y gene, and this extreme resistance is epistatic to hypersensitive resistance. The immunity (R
y-gene) to PVYN was retained through anther culturing and present at all levels of ploidy. The pattern of segregation for immunity was differentiated
according to the ploidy level of the anther-derived plants. This changed segregation pattern may be due to a loss of resistance
during the culturing, when an endoreduplication has taken place or to the possible regeneration from Second-division restituted
unreduced microspores. Anyway, this segregation pattern must be taken into account when gametoclones are used in genetic studies.
Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 4, pp. 572–578.
The text was submitted by the authors in English. 相似文献
11.
Clinton R. Bruce Jong Sam Lee Bente Kiens John A. Hawley 《Obesity (Silver Spring, Md.)》2004,12(7):1158-1165
Objective: To determine the impact of insulin resistance and obesity on muscle triacylglycerol (IMTG) and glycogen metabolism during and after prolonged exercise. Research Methods and Procedures: Female lean (fa/?; N = 40, ZL) and obese insulin-resistant (fa/fa; N = 40, ZO) Zucker rats performed an acute bout of swimming exercise (8 times for 30 minutes) followed by 6 hours of carbohydrate supplementation (CHO) or fasting (FAST). IMTG and glycogen were measured in the extensor digitorum longus (EDL) and red vastus lateralis (RVL) muscles. Results: Despite resting IMTG content being 4-fold higher in ZO compared with ZL rats, IMTG levels were unchanged in either EDL or RVL muscles immediately after exercise. Resting glycogen concentration in EDL and RVL muscles was similar between genotypes, with exercise resulting in glycogen use in both muscles from ZL rats (∼85%, p < 0.05). However, in ZO rats, there was a much smaller decrease in postexercise glycogen content in both EDL and RVL muscles (∼30%). During postexercise recovery, there was a decrease in EDL muscle levels of IMTG in ZL rats supplemented with CHO after 30 and 360 minutes (p < 0.05). In contrast, IMTG content was increased above resting levels in RVL muscles of ZO rats fasted for 360 minutes. Six hours of CHO refeeding restored glycogen content to resting levels in both muscles in ZL rats. However, after 6 hours of FAST in ZO animals, RVL muscle glycogen content was still lower than resting levels (p < 0.05). At this time, IMTG levels were elevated above basal (p < 0.05). Discussion: In both healthy and insulin-resistant skeletal muscle, there was negligible net IMTG degradation after a single bout of prolonged exercise. However, during postexercise recovery, there was differential metabolism of IMTG between phenotypes. 相似文献
12.
Haining Huang Chongkun Zuo Yaqian Zhao Shen Huang Tongkai Wang Min Zhu Jia Li Xiaorong Tao 《Molecular Plant Pathology》2022,23(5):622-633
Sw-5b is an effective resistance gene used widely in tomato to control tomato spotted wilt virus (TSWV), which causes severe losses in crops worldwide. Sw-5b confers resistance by recognizing a 21-amino-acid peptide region of the viral movement protein NSm (NSm21, amino acids 115–135). However, C118Y or T120N mutation within this peptide region of NSm has given rise to field resistance-breaking (RB) TSWV isolates. To investigate the potential ability of TSWV to break Sw-5b-mediated resistance, we mutagenized each amino acid on NSm21 and determined which amino acid mutations would evade Sw-5b recognition. Among all alanine-scan mutants, NSmP119A, NSmW121A, NSmD122A, NSmR124A, and NSmQ126A failed to induce a hypersensitive response (HR) when coexpressed with Sw-5b in Nicotiana benthamiana leaves. TSWV with the NSmP119A, NSmW121A, or NSmQ126A mutation was defective in viral cell-to-cell movement and systemic infection, while TSWV carrying the NSmD122A or NSmR124A mutation was not only able to infect wild-type N. benthamiana plants systemically but also able to break Sw-5b-mediated resistance and establish systemic infection on Sw-5b-transgenic N. benthamiana plants. Two improved mutants, Sw-5bL33P/K319E/R927A and Sw-5bL33P/K319E/R927Q, which we recently engineered and which provide effective resistance against field RB isolates carrying NSmC118Y or NSmT120N mutations, recognized all NSm21 alanine-substitution mutants and conferred effective resistance against new experimental RB TSWV with the NSmD122A or NSmR124A mutation. Collectively, we determined the key residues of NSm for Sw-5b recognition, investigated their potential RB ability, and demonstrated that the improved Sw-5b mutants could provide effective resistance to both field and potential RB TSWV isolates. 相似文献
13.
Net photosynthetic (P
N) and dark respiration (R
D) rate, stomatal (rs′) and internal (ri′) resistances to carbon dioxide were measured by gas exchange methods on leaves of different ages, expressed in leaf plastochron
index units (LPI) for a fast growing poplar cultivar Unal 2. Although the optimal leaf age differs slightly for the different
gas exchange parameters, leaf ontogeny is reflected in the same way in these different parameters. MaximalP
N and minimalrs′ and ri′ values were found at LPI between 6 and 10. Chlorophyll concentrations were lowest at LPI lower than 10 although an
increase in two steps was found, when leaf age increases up to maturity. 相似文献
14.
G. W. Bates A. Zelcer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,83(8):981-986
Summary The hypersensitive response of tobacco to inoculation with tobacco mosaic virus (TMV) is controlled by a single dominant gene, the N gene. As a first step in localizing and transferring the N gene, we have prepared a line of tobacco plants in which the kanamycin-resistance (Kmr) gene is closely linked to the N gene. Nicotiana tabacum plants heterozygous for the N gene were transformed to Kmr by Agrobacterium carrying pMON200. Eighty-nine independent transformed clones were regenerated and were backcrossed with nontransformed, TMV-sensitive plants. Progeny from these crosses were screened first for Kmr; then the Kmr progeny were inoculated with TMV and scored for the hypersensitive response. Of the initial 89 clones, 68 appeared to have integrated a single functional Kmr gene. Initial tests for TMV resistance indicated possible linkage between Kmr and the N gene in 11 plants. With further testing, linkage has been established for two of these plant lines. In one of these lines, the two genes were 30–40 map units apart, and evidence of somatic instability in the linkage was obtained. However, in the second line, linkage between Kmr and the N gene was tight, and recombination between the genes in this case was only 5%. Southern hybridization revealed that this plant contained only a single copy of the Kmr gene. Linkage between Kmr and the N gene in this plant line has been verified in each of two additional backcross generations.Abbreviations
nptII
Neomycin phosphotransferase gene
- Kmr
kanamycin resistant
- Kms
kanamycin sensitive
- TMV
tobacco mosaic virus
- TMV-R
TMV resistant
- TMV-S
TMV sensitive 相似文献
15.
Henri Debray Danuta Dus Jean-Michel Wieruszeski Gérard Strecker Jean Montreuil 《Glycoconjugate journal》1991,8(1):29-37
Four bi-antennary glycan fractions of theN-acetyllactosamine-type, derived from a Lewis lung carcinoma (LL2) cell subline resistant to theAleuria aurantia agglutinin were studied by 400 MHz1H-NMR spectroscopy. By this method, their antennae were found to be terminated either by (2-3 or 6)-linkedN-acetylneuraminic acid or (1-3)-linked galactose residues. The primary structure of glycans of these four glycopeptide or derived oligosaccharide-alditols has been determined in full detail.Abbreviations NAc
N-acetyl group
- NGc
N-glycolyl group
- GlcNAc
N-acetylglucosamine
- NeuAc
N-acetylneuraminic acid
- NeuGc
N-glycolylneuraminic acid
- Man
mannose
- Gal
galactose
- Fuc
fucose
- Con A
concanavalin A
- LCA
Lens culinaris agglutinin
- AAA
Aleuria aurantia agglutinin
- WGA
Wheat germ agglutinin
- RCA II
Ricinus communis agglutinin II
- PBS
phosphate buffered saline, 0.01m Na2HPO4/0.14m NaCl, pH 7.2
- HPLC
high performance liquid chromatography
- EMEM
Eagle's Minimal Essential Medium
- LecR
lectin resistant
- MG
-methylglycoside 相似文献
16.
The cellular processing of three fluorescent N,N-bis(aminoalkyl)-1,4-diaminoanthraquinones (aminoalkyl=2-aminoethyl, 3-aminoprop-1-yl or 4-aminobut-1-yl) and their dinuclear platinum complexes in A2780 human ovarian carcinoma cells with acquired resistance to cisplatin has been monitored over time by time-lapse fluorescence microscopy. The results were compared with the previously reported observations in the parent A2780 cell line. The cellular distribution pattern for the free ligands is similar in sensitive and resistant cells, whereas significant differences in cellular distribution were observed in the case of the platinum complexes. In the cisplatin-resistant cell line the platinum complexes were found to be sequestrated in acidic vesicles in the cytosol from the very beginning of the incubation. This sequestration was not observed in the case of sensitive cells. Platinum accumulation in vesicles possibly presents a mechanism of resistance to platinum complexes. This mechanism appears to be unrelated to the mechanism of deactivation of platinum compounds by glutathione. Encapsulation of the dinuclear platinum complexes in lysosomal vesicles provides a plausible explanation for the decreased activity of these compounds in the resistant cell line, as compared to the sensitive cell line.Abbreviations AQ2 N,N-bis(2-aminoethyl)-1,4-diaminoanthracene-9,10-dione - AQ3 N,N-bis(3-aminoprop-1-yl)-1,4-diaminoanthracene-9,10-dione - AQ4 N,N-bis(4-aminobut-1-yl)-1,4-diaminoanthracene-9,10-dione - l-BSO l-buthionine-S,R-sulfoximine - dien diethylenetriamine - MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide - PAQ2 [{trans-PtCl(NH3)2}2(-AQ2)](NO3)2 - PAQ3 [{trans-PtCl(NH3)2}2(-AQ3)](NO3)2 - PAQ4 [{trans-PtCl(NH3)2}2(-AQ4)](NO3)2 - PAM [{Pt(dien)}2(-AQ2)](NO3)4 - PBS phosphate buffered saline 相似文献
17.
All known gene clusters for glycopeptide antibiotic biosynthesis contain a conserved gene supposed to encode an ABC-transporter.
In the balhimycin-producer Amycolatopsis balhimycina this gene (tba) is localised between the prephenate dehydrogenase gene pdh and the peptide synthetase gene bpsA. Inactivation of tba in A. balhimycina by gene replacement did not interfere with growth and did not affect balhimycin resistance. However, in the supernatant of
the tba mutant RM43 less balhimycin was accumulated compared to the wild type; and the intra-cellular balhimycin concentration was
ten times higher in the tba mutant RM43 than in the wild type. These data suggest that the ABC transporter encoded in the balhimycin biosynthesis gene
cluster is not involved in resistance but is required for the efficient export of the antibiotic. To elucidate the activity
of Tba it was heterologously expressed in Escherichia coli with an N-terminal His-tag and purified by nickel chromatography. A photometric assay revealed that His6-Tba solubilised in dodecylmaltoside possesses ATPase activity, characteristic for ABC-transporters. 相似文献
18.
The N-acetoxy and N-hydroxy derivatives of trans-4-acetylamino-stilbene (AAS) were demonstrated to induce gene mutations at the hgprt locus and to be cytotoxic in V79 cells. These cells deacetylated AAS. Paraoxon inhibited the deacetylation of AAS by more than 99% and reduced the mutagenicicity and cytotoxicity of N-hydroxy-ASS and N-acetoxy-AAS to about one-tenth. Hence, deacetylated metabolites, formed by the target cells, were important for the observed biological effects.Abbreviations AAF
2-acetylaminofluorene
- AAS
trans-4-acetylaminostilbene
- AS
trans-4-aminostilbene 相似文献
19.
R. Hehl E. Faurie J. Hesselbach F. Salamini S. Whitham B. Baker C. Gebhardt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):379-386
The fungus Synchytrium endobioticum, the causal agent of potato wart disease, is subject to world-wide quarKantine regulations due to the production of persistent
resting spores and lack of effective chemical control measures. The selection of Synchytrium-resistant potato cultivars may be facilitated by using markers closely linked with a resistance gene or by transferring a
cloned gene for resistance into susceptible cultivars. Sen1, a gene for resistance to Synchytrium endobioticum race 1, was localized on potato chromosome XI in a genomic region which is related to the tobacco genome segment harbouring
the N gene for resistance to TMV. Using N as probe, we isolated homologous cDNA clones from a Synchytrium-resistant potato line. The N-homologous sequences of potato identified by RFLP mapping a family of resistance gene-like sequences closely linked with
the Sen1 locus. Sequence analysis of two full-length N-homologous cDNA clones revealed the presence of structural domains associated with resistance gene function. One clone (Nl-25)
encodes a polypeptide of 61 kDa and harbours a Toll-interleukin like region (TIR) and a putative nucleotide binding site (NBS).
The other clone (Nl-27) encodes a polypeptide of 95 kDa and harbours besides the TIR and NBS domains five imperfect leucine-rich
repeats (LRRs). Both clones have at their amino terminus a conserved stretch of serine residues that was also found in the
N gene, the RPP5 gene from Arabidopsis thaliana and several other resistance gene homologues, suggesting a function in the resistance response. Cloning of the disease resistance
locus based on map position and the establishment of PCR-based marker assays to assist selection of wart resistant potato
genotypes are discussed.
Received: 4 August 1998 / Accepted: 14 August 1998 相似文献
20.
Aim: To develop an inactivation kinetic model to describe ultraviolet (UV) dose‐response behaviour for micro‐organisms that exhibit tailing using two commonly referenced causes for tailing: physical shielding of micro‐organisms and phenotypic persistence. Methods and Results: Dose‐response data for Escherichia coli, Mycobacterium terrae and Bacillus subtilis spores exposed to UV radiation were fit to the phenotypic persistence and external shielding (PPES) model. The fraction of persistent micro‐organisms in the original population (Npersistent/Ntotal) that exhibited reduced sensitivity to UV radiation was estimated by the PPES model as approx. 10?7, 10?5 and 10?4 for E. coli, B. subtilis spores and Myco. terrae, respectively. Particle shielding effects were evaluated for Myco. terrae and resulted in additional reduction in UV sensitivity. Conclusions: Tailing occurred in laboratory experiments even when clumping and shielding were eliminated as major factors in UV resistance, suggesting that phenotypic persistence in addition to shielding may be important to consider when evaluating dose‐response curves for disinfection applications. Significance and Impact of the Study: The PPES model provides a mechanistically plausible tool for estimating the dose–response behaviour for micro‐organisms that exhibit tailing in dispersed and aggregated settings. Accurate dose‐response behaviour (including the tailing region) is critical to the analysis and validation of all UV disinfection systems. 相似文献