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At least 541 records · Page 30Linked to original sources
PubMed2003

Laminarin elicits defense responses in grapevine and induces protection against Botrytis cinerea and Plasmopara viticola.

Grapevine (Vitis vinifera L.) is susceptible to many pathogens, such as Botrytis cinerea, Plasmopara viticola, Uncinula necator, and Eutypa lata. Phytochemicals are used intensively in vineyards to limit pathogen infections, but the appearance of pesticide-resistant pathogen strains and a desire to protect the environment require that alternative strategies be found. In the present study, the beta-1,3-glucan laminarin derived from the brown algae Laminaria digitata was shown both to be an efficient elicitor of defense responses in grapevine cells and plants and to effectively reduce B. cinerea and P. viticola development on infected grapevine plants. Defense reactions elicited by laminarin in grapevine cells include calcium influx, alkalinization of the extracellular medium, an oxidative burst, activation of two mitogen-activated protein kinases, expression of 10 defense-related genes with different kinetics and intensities, increases in chitinase and beta-1,3-glucanase activities, and the production of two phytoalexins (resveratrol and epsilon-viniferin). Several of these effects were checked and confirmed in whole plants. Laminarin did not induce cell death. When applied to grapevine plants, laminarin reduced infection by B. cinerea and P. viticola by approximately 55 and 75%, respectively. Our data describing a large set of defense reactions in grapevine indicate that the activation of defense responses using elicitors could be a valuable strategy to protect plants against pathogens.

Base Sequence↗
PubMed2003

The endopolygalacturonase 1 from Botrytis cinerea activates grapevine defense reactions unrelated to its enzymatic activity.

A purified glycoprotein from Botrytis cinerea (strain T4), identified as endopolygalacturonase 1 (T4BcPG1) by mass spectrometry analysis, has been shown to activate defense reactions in grapevine (Vitis vinifera cv. Gamay). These reactions include calcium influx, production of active oxygen species, activation of two mitogen-activated protein kinases, defense gene transcript accumulation, and phytoalexin production. Most of these defense reactions were also activated in grapevine in response to purified oligogalacturonides (OGA) with a degree of polymerization of 9 to 20. In vivo, these active OGA might be a part of the released products resulting from endopolygalacturonase activity on plant cell walls. Nevertheless, the intensity and kinetics of events triggered by OGA were very different when compared with T4BcPG1 effects. Moreover, chemical treatments of T4BcPG1 and desensitization assays have allowed us to discriminate enzymatic and elicitor activities, indicating that elicitor activity was not due to released oligogalacturonides. Thus, BcPG1 should be considered as both an avirulence and a virulence factor. The role of the secreted BcPG1 in the pathogenicity of Botrytis cinerea is discussed.

Amino Acid Sequence↗
PubMed2004

Killer toxin of Pichia membranifaciens and its possible use as a biocontrol agent against grey mould disease of grapevine.

The use of Pichia membranifaciens CYC 1106 killer toxin against Botrytis cinerea was investigated. This strain exerted a broad-specificity killing action against other yeasts and fungi. At pH 4, optimal killer activity was observed at temperatures up to 20 degrees C. At 25 degrees C the toxic effect was reduced to 70%. The killer activity was higher in acidic medium. Above about pH 4.5 activity decreased sharply and was barely noticeable at pH 6. The killer toxin protein from P. membranifaciens CYC 1106 was purified to electrophoretic homogeneity. SDS-PAGE of the purified killer protein indicated an apparent molecular mass of 18 kDa. Killer toxin production was stimulated in the presence of non-ionic detergents. The toxin concentrations present in the supernatant during optimal production conditions exerted a fungicidal effect on a strain of B. cinerea. The symptoms of infection and grey mould observed in Vitis vinifera plants treated with B. cinerea were prevented in the presence of purified P. membranifaciens killer toxin. The results obtained suggest that P. membranifaciens CYC 1106 killer toxin is of potential use in the biocontrol of B. cinerea.

Botrytis↗
PubMed2005

Complete genome sequences of two new variants of Grapevine rupestris stem pitting-associated virus and comparative analyses.

Grapevine rupestris stem pitting-associated virus (GRSPaV), a member of the genus Foveavirus within the family Flexiviridae, is the putative causal agent of the disease Rupestris stem pitting (RSP) of grapevines. GRSPaV comprises a family of variants whose pathological characteristics have not been determined. Recently, many of the indicator "St George" plants (Vitis rupestris) used throughout the world to index RSP tested positive for GRSPaV. This finding questions the validity of past biological indexing results. In this work, a representative genomic region of GRSPaV was first sequenced from ten "St George" plants from two sources and it was demonstrated that nine of them carried a new variant, GRSPaV-SG1. The genomes of GRSPaV-SG1 and GRSPaV-BS from "Bertille Seyve 5563" plants were sequenced, revealing a genome structure identical to that of GRSPaV-1. It was demonstrated experimentally that infection of "St George" plants with GRSPaV-SG1 is asymptomatic and thus it is proposed that GRSPaV-SG1 infection should not have interfered with the outcome of past indicator indexing. This represents the first attempt to link a GRSPaV variant with pathological properties.

Amino Acid Sequence↗
PubMed2002

VFL, the grapevine FLORICAULA/LEAFY ortholog, is expressed in meristematic regions independently of their fate.

The flowering process in grapevine (Vitis vinifera) takes place in buds and extends for two consecutive growing seasons. To understand the genetic and molecular mechanisms underlying this process, we have characterized grapevine bud development, cloned the grapevine FLORICAULA/LEAFY (FLO/LFY) ortholog, VFL, and analyzed its expression patterns during vegetative and reproductive development. Flowering induction takes place during the first season. Upon induction, the shoot apical meristem begins to produce lateral meristems that will give rise to either inflorescences or tendrils. During the second season, after a winter dormancy period, buds reactivate and inflorescence meristems give rise to flower meristems. VFL is expressed in lateral meristems that give rise to inflorescence and flower meristems, consistent with a role in reproductive development. Furthermore, VFL is also detected in other meristematic regions such as the vegetative shoot apical meristem and the lateral meristems that will give rise to tendrils. VFL is also expressed in leaf primordia and in growing leaf margins until later stages of development. Accumulation of VFL transcripts in cell-proliferating regions suggests a role for VFL not only in flower meristem specification, but also in the maintenance of indeterminacy before the differentiation of derivatives of the apical meristem: flowers, leaves, or tendrils.

Amino Acid Sequence↗
PubMed2003

Sugar-regulated expression of a putative hexose transport gene in grape.

Different lengths of the promoter of grape (Vitis vinifera) VvHT1 (Hexose Transporter 1) gene, which encodes a putative hexose transporter expressed during the ripening of grape, have been transcriptionally fused to the beta-glucuronidase reporter gene. In transgenic tobacco (Nicotiana tabacum) transformed with these constructs, VvHT1 promoters were clearly responsible for the sink organ preferential expression. The potential sugar effectors of VvHT1 promoter were studied in tobacco cv Bright-Yellow 2 cells transformed with chimeric constructs. Glucose (56 mM), sucrose (Suc; 58 mM), and the non-transported Suc isomer palatinose doubled the beta-glucuronidase activity conferred by the VvHT1 promoter, whereas fructose did not affect it. These effects were the strongest with the 2.4-kb promoter, which contains all putative sugar-responsive elements (activating and repressing), but they were also significant with the 0.3-kb promoter, which contains only activating sugar boxes. The induction of VvHT1 expression by both Suc and palatinose was confirmed in the homologous grape berry cell culture. The data provide the first example of a putative sugar transporter, which is induced by both glucose and Suc in higher plants. Although induction of VvHT1 expression by Suc does not require transport, the presence of glucosyl moiety is necessary for Suc sensing. These results provide new insights into sugar sensing and signaling in plants.

Carbohydrates↗
PubMed2003

trans-Resveratrol and grape disease resistance. A dynamical study by high-resolution laser-based techniques.

Two modern laser-based techniques were synchronously applied to study the dynamics of the trans-resveratrol activity in Botrytis cinerea-infected grapes. Direct analysis of trans-resveratrol in both infected and noninfected grapes (Vitis vinifera, Aledo variety) was performed by using an analytical technique incorporating laser desorption coupled with laser resonant ionization and time-of-flight mass spectrometry. On the other hand, one of the most sensitive on-line methods for trace gas detection, laser photoacoustic spectroscopy, was used to investigate the involvement of the plant hormone ethylene (C(2)H(4)) in the B. cinerea grapes interaction and its temporal relationship with the trans-resveratrol content upon infection. The trans-resveratrol content and the ethylene released by noninfected grapes showed an opposite behavior. In this case, a high trans-resveratrol content corresponds to a low ethylene emission. For the B. cinerea-infected grapes, ethylene emission rises up after 48 h when the analogous content of trans-resveratrol started to decrease irreversibly. Moreover, the activity of trans-resveratrol as natural pesticide has been investigated by exogenous application on grapes. A short submerge (5 s) of the grapes in 1.6 x 10(-4) M solution of trans-resveratrol delays the increase of C(2)H(4) emission with about 48 h and produces a decrease of the C(2)H(4) concentration and its emission rate. The treatment has positive effects on fruit conservation during storage; it doubled the normal shelf-life of grapes at room temperature, maintaining their post-harvest quality within 10 d.

Botrytis↗
PubMed2002

A grapevine gene encoding a guard cell K(+) channel displays developmental regulation in the grapevine berry.

SIRK is a K(+) channel identified in grapevine (Vitis vinifera), belonging to the so-called Shaker family. The highest sequence similarities it shares with the members of this family are found with channels of the KAT type, although SIRK displays a small ankyrin domain. This atypical feature provides a key to understand the evolution of the plant Shaker family. Expression in Xenopus laevis oocytes indicated that SIRK is an inwardly rectifying channel displaying functional properties very similar to those of KAT2. The activity of SIRK promoter region fused to the GUS reporter gene was analyzed in both grapevine and Arabidopsis. Like other KAT-like channels, SIRK is expressed in guard cells. In Arabidopsis, the construct is also expressed in xylem parenchyma. Semiquantitative reverse transcriptase-polymerase chain reaction experiments indicated that SIRK transcript was present at low levels in the berry, during the first stages of berry growth. After veraison, the period of berry development that corresponds to the inception of ripening and that is associated with large biochemical and structural modifications, such as evolution of stomata in nonfunctional lenticels and degeneration of xylem vasculature, the transcript was no longer detected. The whole set of data suggests that in the berries SIRK is expressed in guard cells and, possibly, in xylem tissues. The encoded channel polypeptide could therefore play a role in the regulation of transpiration and water fluxes in grapevine fruits.

Agrobacterium tumefaciens↗
PubMed2005

Proanthocyanidin synthesis and expression of genes encoding leucoanthocyanidin reductase and anthocyanidin reductase in developing grape berries and grapevine leaves.

Proanthocyanidins (PAs), also called condensed tannins, can protect plants against herbivores and are important quality components of many fruits. Two enzymes, leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR), can produce the flavan-3-ol monomers required for formation of PA polymers. We isolated and functionally characterized genes encoding both enzymes from grapevine (Vitis vinifera L. cv Shiraz). ANR was encoded by a single gene, but we found two highly related genes encoding LAR. We measured PA content and expression of genes encoding ANR, LAR, and leucoanthocyanidin dioxygenase in grape berries during development and in grapevine leaves, which accumulated PA throughout leaf expansion. Grape flowers had high levels of PA, and accumulation continued in skin and seeds from fruit set until the onset of ripening. VvANR was expressed throughout early flower and berry development, with expression increasing after fertilization. It was expressed in berry skin and seeds until the onset of ripening, and in expanding leaves. The genes encoding LAR were expressed in developing fruit, particularly in seeds, but had low expression in leaves. The two LAR genes had different patterns of expression in skin and seeds. During grape ripening, PA levels decreased in both skin and seeds, and expression of genes encoding ANR and LAR were no longer detected. The results indicate that PA accumulation occurs early in grape development and is completed when ripening starts. Both ANR and LAR contribute to PA synthesis in fruit, and the tissue and temporal-specific regulation of the genes encoding ANR and LAR determines PA accumulation and composition during grape berry development.

Base Sequence↗
PubMed2005

Characterization of a grapevine R2R3-MYB transcription factor that regulates the phenylpropanoid pathway.

The ripening of grape (Vitis vinifera) berry is characterized by dramatic changes in gene expression, enzymatic activities, and metabolism that lead to the production of compounds essential for berry quality. The phenylpropanoid metabolic pathway is one of the components involved in these changes. In this study, we describe the cloning and functional characterization of VvMYB5a, a cDNA isolated from a grape L. cv Cabernet Sauvignon berry library. VvMYB5a encodes a protein belonging to a small subfamily of R2R3-MYB transcription factors. Expression studies in grapevine indicate that the VvMYB5a gene is mainly expressed during the early steps of berry development in skin, flesh, and seeds. Overexpression of VvMYB5a in tobacco (Nicotiana tabacum) affects the expression of structural genes controlling the synthesis of phenylpropanoid and impacts on the metabolism of anthocyanins, flavonols, tannins, and lignins. Overexpressing VvMYB5a induces a strong accumulation of several phenolic compounds, including keracyanin (cyanidin-3-rhamnoglucoside) and quercetin-3-rhamnoglucoside, which are the main anthocyanin and flavonol compounds in tobacco. In addition, VvMYB5a overexpression increases the biosynthesis of condensed tannins and alters lignin metabolism. These findings suggest that VvMYB5a may be involved in the control of different branches of the phenylpropanoid pathway in grapevine.

Catechin↗
PubMed2005

The grapevine fleshless berry mutation. A unique genotype to investigate differences between fleshy and nonfleshy fruit.

In flowering plants, fruit morphogenesis is a distinct process following fertilization resulting in the formation of a specialized organ associated with seeds. Despite large variations in types and shapes among species, fleshy fruits share common characteristics to promote seed dispersal by animals such as organ growth and metabolite accumulation to attract animal feeding. The molecular biology of fruit ripening has received considerable attention, but little is known about the determinism of early fruit morphogenesis and why some fruits are fleshy while others lack flesh. We have identified in grapevine (Vitis vinifera) a mutation we have named fleshless berry (flb) that reduces by 20 times the weight of the pericarp at ripening without any effect on fertility or seed size and number. The flb mutation strongly impaired division and differentiation of the most vacuolated cells in the inner mesocarp. The timing of ripening was not altered by the mutation although the accumulation of malic acid in the green stage was noticeably reduced while sucrose content (instead of hexoses) increased during ripening. The mutation segregates as a single dominant locus. These results indicate that the Flb- mutant is suitable material to advance our understanding of the genetic and developmental processes involved in the differentiation of an ovary into a fruit.

Cell Differentiation↗
PubMed2005

Grapes on steroids. Brassinosteroids are involved in grape berry ripening.

Fruit ripening is a unique plant developmental process with direct implications for our food supply, nutrition, and health. In contrast to climacteric fruit, where ethylene is pivotal, the hormonal control of ripening in nonclimacteric fruit, such as grape (Vitis vinifera), is poorly understood. Brassinosteroids (BRs) are steroidal hormones, essential for normal plant growth and development but not previously implicated in the ripening of nonclimacteric fruit. Here we show that increases in endogenous BR levels, but not indole-3-acetic acid (IAA) or GA levels, are associated with ripening in grapes. Putative grape homologs of genes encoding BR biosynthesis enzymes (BRASSINOSTEROID-6-OXIDASE and DWARF1) and the BR receptor (BRASSINOSTEROID INSENSITIVE 1) were isolated, and the function of the grape BRASSINOSTEROID-6-OXIDASE gene was confirmed by transgenic complementation of the tomato (Lycopersicon esculentum) extreme dwarf (dx/dx) mutant. Expression analysis of these genes during berry development revealed transcript accumulation patterns that were consistent with a dramatic increase in endogenous BR levels observed at the onset of fruit ripening. Furthermore, we show that application of BRs to grape berries significantly promoted ripening, while brassinazole, an inhibitor of BR biosynthesis, significantly delayed fruit ripening. These results provide evidence that changes in endogenous BR levels influence this key developmental process. This may provide a significant insight into the mechanism controlling ripening in grapes, which has direct implications for the logistics of grape production and down-stream processing.

Cloning, Molecular↗
PubMed2005

Identification of the flavonoid hydroxylases from grapevine and their regulation during fruit development.

Flavonoids are important secondary metabolites in many fruits, and their hydroxylation pattern determines their color, stability, and antioxidant capacity. Hydroxylation of the B-ring of flavonoids is catalyzed by flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3'5'H), and may also require cytochrome b5. We report the identification of genes encoding F3'H, F3'5'H, and a putative cytochrome b5 from grapevine (Vitis vinifera L. cv Shiraz) and their transcriptional regulation in fruit. Functionality of the genes VvF3'H and VvF3'5'H1 was demonstrated by ectopic expression in petunia (Petunia hybrida), which altered flower color and flavonoid composition as expected. VvF3'H was expressed in grapes before flowering, when 3'-hydroxylated flavonols are made, and all three genes were expressed after flowering, when proanthocyanidins (PAs) are synthesized. In berry skin, expression of all three genes was low at the onset of ripening (véraison) but increased after véraison concomitant with the accumulation of 3'- and 3',5'-hydroxylated anthocyanins. VvF3'H and VvCytoB5 were expressed in seeds but not VvF3'5'H1, consistent with the accumulation of 3'-hydroxylated PAs in this tissue. VvCytoB5 expression was correlated with expression of both VvF3'H and VvF3'5'H1 in the different grape tissues. In contrast to red grapes, where VvF3'H, VvF3'5'H1, and VvCytoB5 were highly expressed during ripening, the expression of VvF3'5'H1 and VvCytoB5 in white grapes during ripening was extremely low, suggesting a difference in transcriptional regulation. Our results show that temporal and tissue-specific expression of VvF3'H, VvF3'5'H1, and VvCytoB5 in grapes is coordinated with the accumulation of the respective hydroxylated flavonols and PAs, as well as anthocyanins. Understanding the regulation of flavonoid hydroxylases could be used to modify flavonoid composition of fruits.

Amino Acid Sequence↗
PubMed2006

Xylella fastidiosa infection and ethylene exposure result in xylem and water movement disruption in grapevine shoots.

It is conventionally thought that multiplication of the xylem-limited bacterium Xylella fastidiosa (Xf) within xylem vessels is the sole factor responsible for the blockage of water movement in grapevines (Vitis vinifera) affected by Pierce's disease. However, results from our studies have provided substantial support for the idea that vessel obstructions, and likely other aspects of the Pierce's disease syndrome, result from the grapevine's active responses to the presence of Xf, rather than to the direct action of the bacterium. The use of magnetic resonance imaging (MRI) to observe the distribution of water within the xylem has allowed us to follow nondestructively the development of vascular system obstructions subsequent to inoculation of grapevines with Xf. Because we have hypothesized a role for ethylene produced in vines following infection, the impact of vine ethylene exposure on obstruction development was also followed using MRI. In both infected and ethylene-exposed plants, MRI shows that an important proportion of the xylem vessels become progressively air embolized after the treatments. The loss of xylem water-transporting function, assessed by MRI, has been also correlated with a decrease in stem-specific hydraulic conductivity (K(S)) and the presence of tyloses in the lumens of obstructed water conduits. We have observed that the ethylene production of leaves from infected grapevines is greater than that from healthy vines and, therefore, propose that ethylene may be involved in a series of cellular events that coordinates the vine's response to the pathogen.

Ethylenes↗
PubMed2007

The grapevine transcription factor VvMYBPA1 regulates proanthocyanidin synthesis during fruit development.

Proanthocyanidins (PAs; or condensed tannins) can protect plants against herbivores, contribute to the taste of many fruits, and act as dietary antioxidants beneficial for human health. We have previously shown that in grapevine (Vitis vinifera) PA synthesis involves both leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR). Here we report the characterization of a grapevine MYB transcription factor VvMYBPA1, which controls expression of PA pathway genes including both LAR and ANR. Expression of VvMYBPA1 in grape berries correlated with PA accumulation during early berry development and in seeds. In a transient assay, VvMYBPA1 activated the promoters of LAR and ANR, as well as the promoters of several of the general flavonoid pathway genes. VvMYBPA1 did not activate the promoter of VvUFGT, which encodes the anthocyanin-specific enzyme UDP-glucose:flavonoid-3-O-glucosyltransferase, suggesting VvMYBPA1 is specific to regulation of PA biosynthesis in grapes. The Arabidopsis (Arabidopsis thaliana) MYB transcription factor TRANSPARENT TESTA2 (TT2) regulates PA synthesis in the seed coat of Arabidopsis. By complementing the PA-deficient seed phenotype of the Arabidopsis tt2 mutant with VvMYBPA1, we confirmed the function of VvMYBPA1 as a transcriptional regulator of PA synthesis. In contrast to ectopic expression of TT2 in Arabidopsis, constitutive expression of VvMYBPA1 resulted in accumulation of PAs in cotyledons, vegetative meristems, leaf hairs, and roots in some of the transgenic seedlings. To our knowledge, this is the first report of a MYB factor that controls genes of the PA pathway in fruit, including both LAR and ANR, and this single MYB factor can induce ectopic PA accumulation in Arabidopsis.

Amino Acid Sequence↗
PubMed2006

Isolation and characterization of rhizosphere bacteria with potential for biological control of weeds in vineyards.

AIMS: Deleterious rhizosphere inhabiting bacteria (DRB) have potential to suppress plant growth. This project focuses on the isolation of DRB with potential for development as commercial products for weed control. METHODS AND RESULTS: Bacteria were isolated from the rhizosphere, rhizoplane, and endorhizosphere of seedlings and mature plants of wild radish (Raphanus raphanistrum), annual ryegrass (Lolium rigidum) and capeweed (Arctotheca calendula) growing in vineyards in the Swan Valley, Western Australia. A majority (81.5%) of the 442 strains was obtained from either rhizospheres or rhizoplanes. Rapid screening techniques were developed to evaluate in the laboratory and glasshouse the effects of bacteria on plants. Strains were screened in the glasshouse for deleterious effects on annual ryegrass, wild radish, grapevine rootlings (Vitis vinifera) and the legume cover crop subterranean clover (Trifolium subterraneum). Three strains were identified using the Biolog system and 16S rRNA gene sequencing as two strains of Pseudomonas fluorescens (WSM3455 and WSM3456) and one strain of Alcaligenes xylosoxidans (WSM3457). One of the P. fluorescens (WSM3455) strain produced hydrogen cyanide, an inhibitor of plant roots and a broad-spectrum antimicrobial compound. CONCLUSIONS: Three strains specifically inhibited wild radish but had no significant deleterious effects on either grapevine rootlings or subterranean clover. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggested manipulation of the weed seedling rhizosphere using identified DRB as a potential biocontrol agent for wild radish.

Bacteria↗
PubMed2006

Isolation of an ethanol-tolerant endospore-forming Gram-negative Brevibacillus sp. as a covert contaminant in grape tissue cultures.

AIMS: To characterize the alcohol-surviving bacterial isolate ARBG1 from in vitro grapes (Vitis vinifera). METHODS AND RESULTS: Two bacterial strains that survived in covert form in grape cultures were isolated from the spent alcohol used for disinfecting the tools of which one (ARBG2) was characterized earlier. The present study describes characterization of the second isolate, ARBG1. Nutrient agar (NA)-derived colonies of ARBG1 displayed consistently Gram-negative staining rods (2-4x0.5-0.6 micro) substantiated by KOH mucoid thread test. Older cultures (3-7 days) showed emergence of Gram-negative staining, oblong, phase-refractile cells with ellipsoidal spores. The growth and sporulation were modified by growth medium and incubation temperature with the optimum around 37 degrees C. Identification attempts involving microscopic, biochemical, Biolog or fatty acid profiling approaches brought in mixed and inconclusive results. PCR amplification of 16S rDNA was not successful with the standard primers 27F and 1492R but with 27F and a modified primer ARBG1-RP1. The identity of the isolate was established as Brevibacillus sp. based on partial 16S rDNA sequence data from eight single colonies with Gram-positive Brevibacillus choshinensis as the closest match (99.5%). Spotting tests on NA employing spore suspension in aqueous ethanol (0%, 25%, 50%, 60%, 70%, 80% or 90%, v/v) indicated unhindered bacterial-survival in alcohol for 1 month, and that at 2 or 4 months revealed 90% ethanol as more sporicidal than lower levels, corroborated by plating results. Grape microcuttings inoculated with ARBG1 showed substantial general colonization of shoots, roots and medium but low endophytic colonization. CONCLUSIONS: The rare type of spore-producing consistently Gram-negative bacterial isolate ARBG1 was identified as Brevibacillus sp. based on 16S rDNA sequence similarity. The alcohol-defying organism was nonpathogenic and survived in covert form in grape cultures. Aqueous 90% ethanol appeared more sporicidal than lower levels. SIGNIFICANCE AND IMPACT OF THE STUDY: Characterization of an unusual endospore-forming Gram-negative bacterium, observation that some bacteria may fall outside the purview of standard 16S rDNA primers, elucidation of the threats of covert bacteria in plant tissue cultures and alcohol-mediated lateral transmission of spore formers, and the revelation that 70-80% ethanol may not be the most effective bactericidal concentration for all bacteria.

Base Sequence↗
PubMed2006

Botrytis cinerea virulence is drastically reduced after disruption of chitin synthase class III gene (Bcchs3a).

Botrytis cinerea is an important phytopathogenic fungus requiring new methods of control. Chitin biosynthesis, which involves seven classes of chitin synthases, could be an attractive target. A fragment encoding one of the class III enzymes was used to disrupt the corresponding Bcchs3a gene in the B. cinerea genome. The resulting mutant exhibited a 39% reduction in its chitin content and an 89% reduction in its in vitro chitin synthase activity, compared with the wild-type strain. Bcchs3a mutant was not affected in its growth in liquid medium, neither in its production of sclerotia, micro- and macroconidia. In contrast, the mutant Bcchs3a was severely impaired in its growth on solid medium. Counterbalancing this defect in radial growth, Bcchs3a mutant presented a large increase in hyphal ramification, resulting in an enhanced aerial growth. Observations by different techniques of microscopy revealed a thick extracellular matrix around the hyphal tips. Moreover, Bcchs3a mutant had a largely reduced virulence on Vitis vinifera and Arabidopsis thaliana leaves.

Arabidopsis↗