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1.
Lipoxygenases (LOXs) are a class of non-heme iron-containing dioxygenases that catalyse oxidation of polyunsaturated fatty acids to produce hydroperoxidation that are in turn converted to oxylipins. Although multiple isoforms of LOXs have been detected in several plants, LOXs in oriental melon have not attracted much attention. Two full-length LOX cDNA clones, CmLOX10 and CmLOX13 which have been isolated from oriental melon (Cucumis melo var. makuwa Makino) cultivar “Yumeiren”, encode 902 and 906 amino acids, respectively. Bioinformatics analysis showed that CmLOX10 and CmLOX13 included all of the typical LOX domains and shared 58.11% identity at the amino acid level with each other. The phylogenetic analysis revealed that CmLOX10 and CmLOX13 were members of the type 2 13-LOX subgroup which are known to be involved in biotic and abiotic stress. Heterologous expression of the full-length CmLOX10 and truncated CmLOX13 in Escherichia coli revealed that the encoded exogenous proteins were identical to the predicted molecular weights and possessed the lipoxygenase activities. The purified CmLOX10 and CmLOX13 recombinant enzymes exhibited maximum activity at different temperature and pH and both had higher affinity for linoleic acid than linolenic acid. Chromatogram analysis of reaction products from the CmLOX10 and CmLOX13 enzyme reaction revealed that both enzymes produced 13S-hydroperoxides when linoleic acid was used as substrate. Furthermore, the subcellular localization analysis by transient expression of the two LOX fusion proteins in tobacco leaves showed that CmLOX10 and CmLOX13 proteins were located in plasma membrane and chloroplasts respectively. We propose that the two lipoxygenases may play different functions in oriental melon during plant growth and development. 相似文献
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Kristen A. Hadfield Jocelyn K.C. Rose Debbie S. Yaver Randy M. Berka Alan B. Bennett 《Plant physiology》1998,117(2):363-373
Ripening-associated pectin
disassembly in melon is characterized by a decrease in molecular mass
and an increase in the solubilization of polyuronide, modifications
that in other fruit have been attributed to the activity of
polygalacturonase (PG). Although it has been reported that PG activity
is absent during melon fruit ripening, a mechanism for PG-independent
pectin disassembly has not been positively identified. Here we provide
evidence that pectin disassembly in melon (Cucumis melo)
may be PG mediated. Three melon cDNA clones with significant homology
to other cloned PGs were isolated from the rapidly ripening cultivar
Charentais (C. melo cv Reticulatus F1 Alpha) and were
expressed at high levels during fruit ripening. The expression pattern
correlated temporally with an increase in pectin-degrading activity and
a decrease in the molecular mass of cell wall pectins, suggesting that
these genes encode functional PGs. MPG1 and MPG2 were closely related
to peach fruit and tomato abscission zone PGs, and MPG3 was closely
related to tomato fruit PG. MPG1, the most abundant melon PG mRNA, was
expressed in Aspergillus oryzae. The culture filtrate
exponentially decreased the viscosity of a pectin solution and
catalyzed the linear release of reducing groups, suggesting that MPG1
encodes an endo-PG with the potential to depolymerize melon fruit cell
wall pectin. Because MPG1 belongs to a group of PGs divergent from the
well-characterized tomato fruit PG, this supports the involvement
of a second class of PGs in fruit ripening-associated pectin
disassembly.Fruit ripening is a genetically programmed event that is
characterized by a number of biochemical and physiological processes
that alter fruit color, flavor, aroma, and texture (Brady, 1987).
Extensive cell wall modifications occur during ripening and are thought
to underlie processes such as fruit softening, tissue deterioration,
and pathogen susceptibility. These modifications are regulated at least
in part by the expression of genes that encode cell wall-modifying
enzymes (Fischer and Bennett, 1991). Pectins are a major class of cell
wall polysaccharides that are degraded during ripening, undergoing both
solubilization and depolymerization. In tomato the majority of
ripening-associated pectin degradation is attributable to the cell wall
hydrolase PG. Transgenic tomato plants with altered PG gene expression
indicated that PG-dependent pectin degradation is neither required nor
sufficient for tomato fruit softening to occur (Sheehy et al., 1988;
Smith et al., 1988; Giovannoni et al., 1989). However, data from
experiments using fruit of the same transgenic lines strongly suggested
that PG-mediated pectin degradation is important in the later,
deteriorative stages of ripening and in pathogen susceptibility of
tomato fruit (Schuch et al., 1991; Kramer et al., 1992).In melon (Cucumis melo) substantial amounts of pectin
depolymerization and solubilization take place during ripening
(McCollum et al., 1989; Ranwala et al., 1992; Rose et al., 1998),
implicating a role for PG in ripening-associated cell wall disassembly
in melons. However, melons have been reported to lack PG enzyme
activity (Hobson, 1962; Lester and Dunlap, 1985; McCollum et al., 1989;
Ranwala et al., 1992). The possibility exists that PG is present in
melon but that it does not conform to the expected enzymic properties
in terms of abundance and/or lability, a point illustrated by recent
reports in apple and strawberry, which were previously reported to lack
PG activity but that do in fact accumulate low amounts of protein
and/or measurable activity (Nogata et al., 1993; Wu et al., 1993). In
light of the unexplained discrepancy between ripening-associated pectin
depolymerization and undetectable PG activity in melons, we have
undertaken a study to reexamine the status of PG in melon using the
rapidly ripening cv Charentais (C. melo cv Reticulatus F1
Alpha).As reported for other cultivars, Charentais melons exhibit substantial
solubilization and a downshift in the molecular-mass profile of
water-soluble pectins, but this is associated with the later stages of
ripening, after softening is initiated (Rose et al., 1998). By
utilizing a molecular approach to analyze PG in melon, we have
attempted to overcome some of the potential limitations of biochemical
methods, such as low abundance of protein, reliance on other cell wall
components, and unknown cofactors for activity and/or lability during
extraction. In doing so, we have identified and characterized a
multigene family encoding putative PGs from Charentais melon, including
three PG homologs that are expressed abundantly during fruit ripening.
The pattern of PG gene expression correlates temporally with the
depolymerization of water-soluble pectins and an increase in
pectin-degrading enzyme activity. Three additional PG homologs were
also identified and shown to be expressed in mature anthers and
fruit-abscission zones, tissues that, similar to ripening fruit, are
undergoing cell separation. The most abundant ripening-associated
putative PG mRNA, MPG1, was expressed in the filamentous fungus
Aspergillus oryzae. The culture filtrate from the
transformed A. oryzae strain XMPG1 exhibited
endo-PG activity, further supporting a role for
endo-PG in ripening-associated pectin disassembly in
Charentais melon fruit. 相似文献
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Medieval History of the Duda’im Melon ( Cucumis melo , Cucurbitaceae). Melons, Cucumis melo, are a highly polymorphic species for fruit characteristics. The melons that are the most valued are the ones that turn sweet when ripe, including the muskmelons, cantaloupes, and casabas. Others, including the elongate adzhur, conomon, and snake melons, are consumed when immature, like cucumbers. The duda’im melons, Cucumis melo Duda’im Group, are special, as their small, spherical, thin-fleshed, insipid but beautifully maroon, dark-orange, or brown-and-yellow striped ripe fruits are valued for ornament and especially for their lush fragrance. The distinctive properties of duda’im melons are matched with special names given to them in several languages and geographical areas, which have made possible tracing of the history of these melons to mid-9th century Persia. From that region, duda’im melons diffused westward, likely facilitated by Islamic conquests, reaching North Africa and Andalusia in the 10th century. 相似文献
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Hector G. Nuñez-Palenius Miguel Gomez-Lim Neftali Ochoa-Alejo Rebecca Grumet Gene Lester Daniel J. Cantliffe 《Critical reviews in biotechnology》2013,33(1):13-55
Among Cucurbitaceae, Cucumis melo is one of the most important cultivated cucurbits. They are grown primarily for their fruit, which generally have a sweet aromatic flavor, with great diversity and size (50 g to 15 kg), flesh color (orange, green, white, and pink), rind color (green, yellow, white, orange, red, and gray), form (round, flat, and elongated), and dimension (4 to 200 cm). C. melo can be broken down into seven distinct types based on the previously discussed variations in the species. The melon fruits can be either climacteric or nonclimacteric, and as such, fruit can adhere to the stem or have an abscission layer where they will fall from the plant naturally at maturity. Traditional plant breeding of melons has been done for 100 years wherein plants were primarily developed as open-pollinated cultivars. More recently, in the past 30 years, melon improvement has been done by more traditional hybridization techniques. An improvement in germplasm is relatively slow and is limited by a restricted gene pool. Strong sexual incompatibility at the interspecific and intergeneric levels has restricted rapid development of new cultivars with high levels of disease resistance, insect resistance, flavor, and sweetness. In order to increase the rate and diversity of new traits in melon it would be advantageous to introduce new genes needed to enhance both melon productivity and melon fruit quality. This requires plant tissue and plant transformation techniques to introduce new or foreign genes into C. melo germplasm. In order to achieve a successful commercial application from biotechnology, a competent plant regeneration system of in vitro cultures for melon is required. More than 40 in vitro melon regeneration programs have been reported; however, regeneration of the various melon types has been highly variable and in some cases impossible. The reasons for this are still unknown, but this plays a heavy negative role on trying to use plant transformation technology to improve melon germplasm. In vitro manipulation of melon is difficult; genotypic responses to the culture method (i.e., organogenesis, somatic embryogenesis, etc.) as well as conditions for environmental and hormonal requirements for plant growth and regeneration continue to be poorly understood for developing simple in vitro procedures to culture and transform all C. melo genotypes. In many cases, this has to be done on an individual line basis. The present paper describes the various research findings related to successful approaches to plant regeneration and transgenic transformation of C. melo. It also describes potential improvement of melon to improve fruit quality characteristics and postharvest handling. Despite more than 140 transgenic melon field trials in the United States in 1996, there are still no commercial transgenic melon cultivars on the market. This may be a combination of technical or performance factors, intellectual property rights concerns, and, most likely, a lack of public acceptance. Regardless, the future for improvement of melon germplasm is bright when considering the knowledge base for both techniques and gene pools potentially useable for melon improvement. 相似文献
6.
Manríquez D El-Sharkawy I Flores FB El-Yahyaoui F Regad F Bouzayen M Latché A Pech JC 《Plant molecular biology》2006,61(4-5):675-685
Alcohol dehydrogenases (ADH) participate in the biosynthetic pathway of aroma volatiles in fruit by interconverting aldehydes
to alcohols and providing substrates for the formation of esters. Two highly divergent ADH genes (15% identity at the amino acid level) of Cantaloupe Charentais melon (Cucumis melo var. Cantalupensis) have been isolated. Cm-ADH1 belongs to the medium-chain zinc-binding type of ADHs and is highly similar to all ADH genes expressed in fruit isolated so far. Cm-ADH2 belongs to the short-chain type of ADHs. The two encoded proteins are enzymatically active upon expression in yeast. Cm-ADH1
has strong preference for NAPDH as a co-factor, whereas Cm-ADH2 preferentially uses NADH. Both Cm-ADH proteins are much more
active as reductases with K
ms 10–20 times lower for the conversion of aldehydes to alcohols than for the dehydrogenation of alcohols to aldehydes. They
both show strong preference for aliphatic aldehydes but Cm-ADH1 is capable of reducing branched aldehydes such as 3-methylbutyraldehyde,
whereas Cm-ADH2 cannot. Both Cm-ADH genes are expressed specifically in fruit and up-regulated during ripening. Gene expression as well as total ADH activity
are strongly inhibited in antisense ACC oxidase melons and in melon fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive
regulation by ethylene. These data suggest that each of the Cm-ADH protein plays a specific role in the regulation of aroma
biosynthesis in melon fruit.
Daniel Manríquez and Islam El-Sharkawy contributed equally to the work.
Accession numbers for Cm-ADH1 (ABC02081), and Cm-ADH2 (ABC02082). 相似文献
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Peter H. Adler Tatiana Kúdelová Matú? Kúdela Gunther Seitz Aleksandra Ignjatovi?-?upina 《PloS one》2016,11(1)
The European black fly Simulium (Simulium) colombaschense (Scopoli), once responsible for as many as 22,000 livestock deaths per year, is chromosomally mapped, permitting its evolutionary relationships and pest drivers to be inferred. The species is 12 fixed inversions removed from the standard sequence of the subgenus Simulium. Three of these fixed inversions, 38 autosomal polymorphisms, and a complex set of 12 X and 6 Y chromosomes in 29 zygotic combinations uniquely characterize S. colombaschense and reveal 5 cytoforms: ‘A’ in the Danube watershed, ‘B’ in Italy’s Adige River, ‘C’ in the Aliakmonas River of Greece, ‘D’ in the Aoös drainage in Greece, and ‘E’ in the Belá River of Slovakia. ‘C’ and ‘D’ are reproductively isolated from one another, and ‘B’ is considered a cytotype of ‘A,’ the probable name bearer of colombaschense. The species status of ‘E’ cannot be determined without additional collections. Three derived polytene sequences, based on outgroup comparisons, place S. colombaschense in a clade of species composed of the S. jenningsi, S. malyschevi, and S. reptans species groups. Only cytoforms ‘A’ and ‘B’ are pests. Within the Simuliidae, pest status is reached through one of two principal pathways, both of which promote the production of large populations of blood-seeking flies: (1) colonization of the world’s largest rivers (habitat specialization) or (2) colonization of multiple habitat types (habitat generalization). Evolutionary acquisition of the ability to colonize large rivers by an ancestor of the S. jenningsi-malyschevi-reptans clade set the scene for the pest status of S. colombaschense and other big-river members of the clade. In an ironic twist, the macrogenome of S. colombaschense reveals that the name associated with history’s worst simuliid pest represents a complex of species, two or more of which are nonpests potentially vulnerable to loss of their limited habitat. 相似文献
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Yong-Joon Cho Hana Yi Jongsik Chun Sang-Nae Cho Charles L. Daley Won-Jung Koh Sung Jae Shin 《PloS one》2013,8(11)
Members of the Mycobacterium abscessus complex are rapidly growing mycobacteria that are emerging as human pathogens. The M. abscessus complex was previously composed of three species, namely M. abscessus
sensu stricto, ‘M. massiliense’, and ‘M. bolletii’. In 2011, ‘M. massiliense’ and ‘M. bolletii’ were united and reclassified as a single subspecies within M. abscessus: M. abscessus subsp. bolletii. However, the placement of ‘M. massiliense’ within the boundary of M. abscessus subsp. bolletii remains highly controversial with regard to clinical aspects. In this study, we revisited the taxonomic status of members of the M. abscessus complex based on comparative analysis of the whole-genome sequences of 53 strains. The genome sequence of the previous type strain of ‘Mycobacterium massiliense’ (CIP 108297) was determined using next-generation sequencing. The genome tree based on average nucleotide identity (ANI) values supported the differentiation of ‘M. bolletii’ and ‘M. massiliense’ at the subspecies level. The genome tree also clearly illustrated that ‘M. bolletii’ and ‘M. massiliense’ form a distinct phylogenetic clade within the radiation of the M. abscessus complex. The genomic distances observed in this study suggest that the current M. abscessus subsp. bolletii taxon should be divided into two subspecies, M. abscessus subsp. massiliense subsp. nov. and M. abscessus subsp. bolletii, to correspondingly accommodate the previously known ‘M. massiliense’ and ‘M. bolletii’ strains. 相似文献
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Cynthia Palmieri-Thiers Stéphane Canaan Virginie Brunini Vannina Lorenzi Félix Tomi Jean-Luc Desseyn Ulrike Garscha Ernst H. Oliw Liliane Berti Jacques Maury 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2009,1791(5):339-346
Plant lipoxygenases (LOXs) are a class of widespread dioxygenases catalysing the hydroperoxidation of polyunsaturated fatty acids. Although multiple isoforms of LOX have been detected in a wide range of plants, their physiological roles remain to be clarified. With the aim to clarify the occurrence of LOXs in olives and their contribution to the elaboration of the olive oil aroma, we cloned and characterized the first cDNA of the LOX isoform which is expressed during olive development. The open reading frame encodes a polypeptide of 864 amino acids. This olive LOX is a type-1 LOX which shows a high degree of identity at the peptide level towards hazelnut (77.3%), tobacco (76.3%) and almond (75.5%) LOXs. The recombinant enzyme shows a dual positional specificity, as it forms both 9- and 13-hydroperoxide of linoleic acid in a 2:1 ratio, and would be defined as 9/13-LOX. Although a LOX activity was detected throughout the olive development, the 9/13-LOX is mainly expressed at late developmental stages. Our data suggest that there are at least two Lox genes expressed in black olives, and that the 9/13-LOX is associated with the ripening and senescence processes. However, due to its dual positional specificity and its expression pattern, its contribution to the elaboration of the olive oil aroma might be considered. 相似文献
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Ekaterina Papadopoulou Holly Ann Little Sue Ann Hammar Rebecca Grumet 《Sexual plant reproduction》2005,18(3):131-142
Members of the Cucurbitaceae family display a range of sexual phenotypes including various combinations of male, female, or
bisexual flowers. Ethylene appears to be a key hormone regulating the sex determination process. Application of ethylene,
or inhibition of ethylene action, increases or decreases the number of pistil-bearing buds, respectively. Elevated levels
of ethylene production and expression of genes for ethylene biosynthesis, have been correlated with pistillate flower production.
In this study, we sought to determine the effect of modified endogenous ethylene production on sex expression by constitutively
expressing ACS (1-aminocyclopropane-1-carboxylate synthase), the first committed enzyme for ethylene biosynthesis, in transgenic melons
(Cucumis melo L.). Most melon genotypes are andromonoecious, where an initial phase of male flowers is followed by a mixture of bisexual
and male flowers. ACS melon plants showed increased ethylene production by leaves and flower buds, and increased femaleness as measured by earlier
and increased number of bisexual buds. ACS melons also had earlier and increased number of bisexual buds that matured to anthesis, suggesting that ethylene is important
not only for sex determination, but also for development of the bisexual bud to maturity. Field studies showed that ACS melons had earlier mature bisexual flowers, earlier fruit set, and increased number of fruit set on closely spaced nodes
on the main stem. These results provide a direct demonstration of the importance of endogenous ethylene production for female
reproductive processes in melon. 相似文献
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Qiong Lin Shaojia Li Wencheng Dong Chao Feng Xueren Yin Changjie Xu Chongde Sun Kunsong Chen 《PloS one》2015,10(3)
Citrate is the predominant organic acid associated with taste in citrus fruit. Although citrate metabolism has been widely studied in recent years, the potential contributions of transport proteins to citrate content remain unclear. In the present study, high-acid citrus fruit Gaocheng (‘GC’, Citrus sp.) and low-acid citrus fruit Satsuma mandarin (‘SM’, Citrus unshiu Marc.) were selected for study, and the degradation of citrate was deduced to be the main cause of the difference in acidity in fully mature fruits. RNA-seq analysis was carried out on ‘GC’ and ‘SM’ fruit samples over the same time course, and the results indicated that citrate degradation occurred mainly through the glutamine pathway, catalyzed by CitAco3-CitGS2-CitGDU1, and also two transport-related genes, CitCHX and CitDIC, were shown to be associated with citrate degradation. These results were confirmed by real-time PCR. In postharvest ‘GC’ fruit, the expressions of these two transport-related genes were induced by 2-fold under hot air treatment, accompanied by a reduction of 7%-9% in total acid degradation. Transient expression of CitCHX and CitDIC in tobacco leaves was performed, and the citrate content was reduced by 62%, 75% and 78% following CitCHX, CitDIC and CitCHX plus CitDIC treatments, respectively, as compared with expression of an empty vector. Overall, these data indicated that two transport proteins, CitCHX and CitDIC, are not only involved in citrate degradation during fruit development, but also involved in postharvest hot air triggered citrate reduction. 相似文献
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Ismail Bezirganoglu Shaw-Yhi Hwang Tony J. Fang Jei-Fu Shaw 《Plant Cell, Tissue and Organ Culture》2013,112(2):227-237
The oriental melon (Cucumis melo L. var. makuwa cv. ‘Silver Light’) is an important fruit crop in the tropical and subtropical regions. However, oriental melon production is severely decreased by fungal diseases. In this study, antifungal protein (AFP) and chitinase (CHI) fusion genes were introduced into oriental melons to control fungal diseases caused by Rhizoctonia solani and Fusarium oxysporum. Transformation of oriental melon (Cucumis melo L. var. makuwa cv. ‘Silver Light’) with Agrobacterium tumefaciens strain LBA4404 containing antifungal protein (AFP) and chitinase (CHI) fusion genes under the control of the cauliflower mosaic virus (CaMV) 35S promoter and neomycin phosphotransferase (nptII) gene as a selectable marker was performed. Cotyledon explants of oriental melon were inoculated by Agrobacterium suspensions with pBI121–AFP–CHI and cultured in a regeneration medium. After regeneration, genomic DNA polymerase chain reaction (PCR) was conducted to confirm the presence of putative transgenic shoots. Southern blot analysis confirmed that the AFP–CHI fusion gene was incorporated into the genomic DNA of the PCR-positive lines. RT-PCR analysis showed that the AFP–CHI fusion gene was expressed in the individual transgenic lines. Western blot analysis revealed the accumulation of CHI protein in leaves. A segregation analysis of the T1 generation confirmed the inheritance of the transgene. Our results demonstrated that the AFP–CHI fusion gene was effective in protecting the transgenic melon plants against fungal disease caused by Rhizoctonia solani and Fusarium oxysporum. 相似文献
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Teresa Delgado-Goñi Sonia Campo Juana Martín-Sitjar Miquel E. Cabañas Blanca San Segundo Carles Arús 《Planta》2013,238(2):397-413
In most plants, sucrose is the primary product of photosynthesis, the transport form of assimilated carbon, and also one of the main factors determining sweetness in fresh fruits. Traditional methods for sugar quantification (mainly sucrose, glucose and fructose) require obtaining crude plant extracts, which sometimes involve substantial sample manipulation, making the process time-consuming and increasing the risk of sample degradation. Here, we describe and validate a fast method to determine sugar content in intact plant tissue by using high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). The HR-MAS NMR method was used for quantifying sucrose, glucose and fructose in mesocarp tissues from melon fruits (Cucumis melo var. reticulatus and Cucumis melo var. cantalupensis). The resulting sugar content varied among individual melons, ranging from 1.4 to 7.3 g of sucrose, 0.4–2.5 g of glucose; and 0.73–2.83 g of fructose (values per 100 g fw). These values were in agreement with those described in the literature for melon fruit tissue, and no significant differences were found when comparing them with those obtained using the traditional, enzymatic procedure, on melon tissue extracts. The HR-MAS NMR method offers a fast (usually <30 min) and sensitive method for sugar quantification in intact plant tissues, it requires a small amount of tissue (typically 50 mg fw) and avoids the interferences and risks associated with obtaining plant extracts. Furthermore, this method might also allow the quantification of additional metabolites detectable in the plant tissue NMR spectrum. 相似文献
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Navot Galpaz Itay Gonda Doron Shem‐Tov Omer Barad Galil Tzuri Shery Lev Zhangjun Fei Yimin Xu Linyong Mao Chen Jiao Rotem Harel‐Beja Adi Doron‐Faigenboim Oren Tzfadia Einat Bar Ayala Meir Uzi Sa'ar Aaron Fait Eran Halperin Merav Kenigswald Elazar Fallik Nadia Lombardi Guy Kol Gil Ronen Yosef Burger Amit Gur Ya'akov Tadmor Vitaly Portnoy Arthur A. Schaffer Efraim Lewinsohn James J. Giovannoni Nurit Katzir 《The Plant journal : for cell and molecular biology》2018,94(1):169-191
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Citrus greening (huanglongbing) is the most destructive citrus disease worldwide. The disease is associated with three species of ‘Candidatus Liberibacter’ among which ‘Ca. Liberibacter asiaticus’ has the widest distribution. ‘Ca. L. asiaticus’ is commonly transmitted by a phloem-feeding insect vector, the Asian citrus psyllid Diaphorina citri. A previous study showed that isolates of ‘Ca. L. asiaticus’ were clearly differentiated by variable number of tandem repeat (VNTR) profiles at four loci in the genome. In this study, the VNTR analysis was further validated by assessing the stability of these repeats after multiplication of the pathogen upon host-to-host transmission using a ‘Ca. L. asiaticus’ strain from Japan. The results showed that some tandem repeats showed detectable changes after insect transmission. To our knowledge, this is the first report to demonstrate that the repeat numbers VNTR 002 and 077 of ‘Ca. L. asiaticus’ change through psyllid transmission. VNTRs in the recipient plant were apparently unrelated to the growing phase of the vector. In contrast, changes in the number of tandem repeats increased with longer acquisition and inoculation access periods, whereas changes were not observed through psyllid transmission after relatively short acquisition and inoculation access periods, up to 20 and 19 days, respectively. 相似文献
20.
Little is known about the effects of NaCl stress on perennial ryegrass (Lolium perenne L.) photosynthesis and carbohydrate flux. The objective of this study was to understand the carbohydrate metabolism and identify the gene expression affected by salinity stress. Seventy-four days old seedlings of two perennial ryegrass accessions (salt-sensitive ‘PI 538976’ and salt-tolerant ‘Overdrive’) were subjected to three levels of salinity stress for 5 days. Turf quality in all tissues (leaves, stems and roots) of both grass accessions negatively and significantly correlated with GFS (Glu+Fru+Suc) content, except for ‘Overdrive’ stems. Relative growth rate (RGR) in leaves negatively and significantly correlated with GFS content in ‘Overdrive’ (P<0.01) and ‘PI 538976’ (P<0.05) under salt stress. ‘Overdrive’ had higher CO2 assimilation and Fv/Fm than ‘PI 538976’. Intercellular CO2 concentration, however, was higher in ‘PI 538976’ treated with 400 mM NaCl relative to that with 200 mM NaCl. GFS content negatively and significantly correlated with RGR in ‘Overdrive’ and ‘PI 538976’ leaves and in ‘PI 538976’ stems and roots under salt stress. In leaves, carbohydrate allocation negatively and significantly correlated with RGR (r2 = 0.83, P<0.01) and turf quality (r2 = 0.88, P<0.01) in salt-tolerant ‘Overdrive’, however, the opposite trend for salt-sensitive ‘PI 538976’ (r2 = 0.71, P<0.05 for RGR; r2 = 0.62, P>0.05 for turf quality). A greater up-regulation in the expression of SPS, SS, SI, 6-SFT gene was observed in ‘Overdrive’ than ‘PI 538976’. A higher level of SPS and SS expression in leaves was found in ‘PI 538976’ relative to ‘Overdrive’. Accumulation of hexoses in roots, stems and leaves can induce a feedback repression to photosynthesis in salt-stressed perennial ryegrass and the salt tolerance may be changed with the carbohydrate allocation in leaves and stems. 相似文献