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In the present investigative study, fifty Trichoderma spp. (Persoon) were isolated from the rhizosphere of various crop plants. Their potential, as an antagonist was assessed against S. sclerotiorum (Lib.) de Bary , causing stem rot of carnation ( Dianthus caryophyllus L.). T. asperellum (NVTA2) was superior in inhibiting the growth and development of stem rot pathogen up to 53.7 per cent in vitro . Seven Trichoderma species with greatest antagonistic potential were identified up to species level through molecular characterization. They were identified as T. asperellum (NVTA1, NVTA2), T. harzianum (NVTH1, NVTH2), T. citrinoviride (NVTC1, NVTC2), and T. erinaceum (NVTE1). Effective strains were screened for the presence of cellobiohydrolase ( cbh1 ) and endochitinase ( ech42 ) genes through PCR. Among the seven strains, T. asperellum (NVTA2) alone had both genes. Crude metabolite extracted from T. asperellum (NVTA2), effectively inhibited the mycelial growth of S. sclerotiorum up to 374.4 mm 2 . GC/MS profiling of crude extract revealed the presence of antifungal compounds including aliphatic hydrocarbons, terpenes and fatty acids. Root dipping and soil application of talc formulations of the seven Trichoderma spp. revealed that T. asperellum (NVTA2) effectively suppressed disease incidence up to 11.8 (PDI-Percent Disease Incidence) compared to the control (37.9 PDI), resulting in approximately 69% reduction. More over NVTA2 also promoted plant growth that resulted in increase in shoot numbers (6.60/plant), stalk length (72.7 cm) and flower yield (205.9 numbers/m 2 ), which were comparatively greater than control. [ABSTRACT FROM AUTHOR]

The perception of pathogen-associated molecular patterns (PAMPs) by immune receptors launches defence mechanisms referred to as PAMP-triggered immunity (PTI). Successful pathogens must suppress PTI pathways via the action of effectors to efficiently colonize their hosts. So far, plant PTI has been reported to be active against most classes of pathogens, except viruses, although this defence layer has been hypothesized recently as an active part of antiviral immunity which needs to be suppressed by viruses for infection success. Here, we report that Arabidopsis PTI genes are regulated upon infection by viruses and contribute to plant resistance to Plum pox virus (PPV). Our experiments further show that PPV suppresses two early PTI responses, the oxidative burst and marker gene expression, during Arabidopsis infection. In planta expression of PPV capsid protein (CP) was found to strongly impair these responses in Nicotiana benthamiana and Arabidopsis, revealing its PTI suppressor activity. In summary, we provide the first clear evidence that plant viruses acquired the ability to suppress PTI mechanisms via the action of effectors, highlighting a novel strategy employed by viruses to escape plant defences. [ABSTRACT FROM AUTHOR]

Apple scab (Venturia inaequalis (Cke) Wint) is the main disease of apple trees not only in the world but also in Turkey. The disease can cause severe yield losses in all Turkish apple orchards. Genetic diversity and relatedness of apple scab (Venturia inaequalis (Cke) Wint) isolates collected from Turkey and Europe were investigated in this study through molecular markers. RAPD, ISSR, SSR and SRAP markers were used in the molecular studies. Results obtained by marker system revealed that isolates were quite separated from each other and it is appeared to exist a variation between them. Genetic relatedness between the isolates are very close to each other, and difference among the groups is not significant due to host specificity and geographical location. The groups are consisted of more number of isolates when SSR and SRAP markers are used compared with ISSR and RAPD markers. Using SSR and SRAP markers are preferable to provide more informative outcomes because of ease of use, repeatability and specificity. [ABSTRACT FROM AUTHOR]

Investigating the origin and dispersal pathways is instrumental to mitigate threats and economic and environmental consequences of invasive crop pathogens. In the case of Puccinia striiformis causing yellow rust on wheat, a number of economically important invasions have been reported, e.g., the spreading of two aggressive and high temperature adapted strains to three continents since 2000. The combination of sequence-characterized amplified region ( SCAR) markers, which were developed from two specific AFLP fragments, differentiated the two invasive strains, PstS1 and PstS2 from all other P. striiformis strains investigated at a worldwide level. The application of the SCAR markers on 566 isolates showed that PstS1 was present in East Africa in the early 1980s and then detected in the Americas in 2000 and in Australia in 2002. PstS2 which evolved from PstS1 became widespread in the Middle East and Central Asia. In 2000, PstS2 was detected in Europe, where it never became prevalent. Additional SSR genotyping and virulence phenotyping revealed 10 and six variants, respectively, within PstS1 and PstS2, demonstrating the evolutionary potential of the pathogen. Overall, the results suggested East Africa as the most plausible origin of the two invasive strains. The SCAR markers developed in the present study provide a rapid, inexpensive, and efficient tool to track the distribution of P. striiformis invasive strains, PstS1 and PstS2. [ABSTRACT FROM AUTHOR]

Lysobacter capsici AZ78 has considerable potential for biocontrol of phytopathogenic microorganisms. However, lack of information about genetic cues regarding its biological characteristics may slow down its exploitation as a biofungicide. In order to obtain a comprehensive overview of genetic features, the L. capsici AZ78 genome was sequenced, annotated and compared with the phylogenetically related pathogens Stenotrophomonas malthophilia K729a and Xanthomonas campestris pv. campestris ATCC 33913. Whole genome comparison, supported by functional analysis, indicated that L. capsici AZ78 has a larger number of genes responsible for interaction with phytopathogens and environmental stress than S. malthophilia K729a and X. c. pv. campestris ATCC 33913. Genes involved in the production of antibiotics, lytic enzymes and siderophores were specific for L. capsici AZ78, as well as genes involved in resistance to antibiotics, environmental stressors, fungicides and heavy metals. The L. capsici AZ78 genome did not encompass genes involved in infection of humans and plants included in the S. malthophilia K729a and X. c. pv. campestris ATCC 33913 genomes, respectively. The L. capsici AZ78 genome provides a genetic framework for detailed analysis of other L. capsici members and the development of novel biofungicides based on this bacterial strain. [ABSTRACT FROM AUTHOR]

This study used both microscopic and biochemical analyses to investigate the possible defense responses induced by acibenzolar-S-methyl (ASM) and potassium phosphite (Phi) in mango plants inoculated with Ceratocystis fimbriata. Disease development was evaluated in the stems of inoculated mango plants and these were examined using fluorescence and light microscopy. High-performance liquid chromatography (HPLC) was used to quantify secondary metabolites in the stem sections. Spraying the plants with ASM and Phi reduced internal necrosis and disease development. The ASM and Phi induced many microscopic defense responses in the stem tissues against C. fimbriata infection. HPLC analysis revealed that the concentrations of two alkaloids (theobromine and 7-methylxanthine) and 10 phenolic compounds (catechin, epicatechin, epigallocatechin, gallic acid, myricetin. pcoumaric acid, p-hydroxybenzoic acid, phloridzin, sinapinic acid, and salicylhydroxamic acid) were higher in the stem tissues of plants sprayed with ASM or Phi than in inoculated control treatment. The concentrations of phenolic compounds were higher in the stem tissues of inoculated plants than in noninoculated plants, while the inverse was observed for alkaloids. Higher concentrations of secondary metabolites in the stem tissues were detected in the early stages of fungal infection, especially in plants treated with inducers. Taken together, the results from the present study clearly support the concept that the phenylpropanoid pathway in the stem tissues of mango plants infected by C. fimbriata can be induced by ASM and Phi. [ABSTRACT FROM AUTHOR]

Silver Genetic diversity of Colletotrichum falcatum causing red rot of sugarcane was assessed based on morphological, pathological and molecular characteristics especially from sub-tropical Indian conditions. Sixteen isolates of this pathogen were collected based on the extensive survey on prominent varieties grown in the region along with some elite selections. Morphological observations (colony colour, mycelium pattern and sporulation) grouped the isolates into two distinct types (C1: light type and C2: dark type). However, quantitative data on colony diameter showed five clusters for these isolates. Pathogenic characterization of these isolates on fourteen standard differentials formed six groups, ingroup 1: (CF-Pb-1) isolates Cf-157, Cf-249 and Cf-248 were the most virulent while group 6 (CF-Pb-6) isolates Cf-60 and Cf-247 were the least one. The genetic relatedness among the isolates using Random Amplified Polymorphic DNA (RAPD) analysis revealed sufficient molecular polymorphism, which in turn confirmed the variation in virulence of different isolates. The data categorized different isolates into two major clusters and five independent lineages. Polymorphic information content (PIC) ranged from 0.701 to 0.929. Isolate Cf-223 was found to be genetically most diverse among all the isolates. Present study inferred that morphological grouping of most of the isolates showed positive correlation with the pathogenic variability while molecular diversity did not showed such associations. [ABSTRACT FROM AUTHOR]

Phytoplasmas are plant pathogenic bacteria associated with devastating damage to over 700 plant species worldwide. It is agriculturally important to identify factors involved in their pathogenicity and to discover effective measures to control phytoplasma diseases. Despite their economic importance, phytoplasmas remain the most poorly characterized plant pathogens, primarily because efforts at in vitro culture, gene delivery, and mutagenesis have been unsuccessful. However, recent molecular studies have revealed unique biological features of phytoplasmas. This review summarizes the history and recent progress in phytoplasma research, focusing on (1) the discovery of phytoplasmas, (2) molecular classification of phytoplasmas, (3) diagnosis of phytoplasma diseases, (4) reductive evolution of the genomes, (5) characteristic features of the plasmids, (6) molecular mechanisms of insect transmissibility, and (7) virulence factors involved in their unique symptoms. [ABSTRACT FROM AUTHOR]

The authors reflect on the limited knowledge of bacterial plant pathogen Ralstonia solanacearum and its type III secretion system. They discuss the regulatory mechanism of type III secretion system and the bacterial virulence in plants. They mention the type III effector function, the effector co-regulated system, and methods used to study effectors promoting growth in plants.

We report the use of designer transcription activator-like (TAL) effectors (dTALEs) for gene activation and function analysis in plants. Seven dTALEs tested all induce their corresponding target genes and some trigger disease susceptibility or resistance to the bacteria expressing them in rice.TAL (transcription activator-like) effectors from Xanthomonas bacteria activate the cognate host genes, leading to disease susceptibility or resistance dependent on the genetic context of host target genes. The modular nature and DNA recognition code of TAL effectors enable custom-engineering of designer TAL effectors (dTALE) for gene activation. However, the feasibility of dTALEs as transcription activators for gene functional analysis has not been demonstrated. Here, we report the use of dTALEs, as expressed and delivered by the pathogenic Xanthomonas oryzae pv. oryzae (Xoo), in revealing the new function of two previously identified disease-related genes and the potential of one developmental gene for disease susceptibility in rice/Xoo interactions. The dTALE gene dTALE-xa27, designed to target the susceptible allele of the resistance gene Xa27, elicited a resistant reaction in the otherwise susceptible rice cultivar IR24. Four dTALE genes were made to induce the four annotated Xa27 homologous genes in rice cultivar Nipponbare, but none of the four induced Xa27-like genes conferred resistance to the dTALE-containing Xoo strains. A dTALE gene was also generated to activate the recessive resistance gene xa13, an allele of the disease-susceptibility gene Os8N3 (also named Xa13 or OsSWEET11, a member of sucrose efflux transporter SWEET gene family). The induction of xa13 by the dTALE rendered the resistant rice IRBB13 (xa13/xa13) susceptible to Xoo. Finally, OsSWEET12, an as-yet uncharacterized SWEET gene with no corresponding naturally occurring TAL effector identified, conferred susceptibility to the Xoo strains expressing the corresponding dTALE genes. Our results demonstrate that dTALEs can be delivered through the bacterial secretion system to activate genes of interest for functional analysis in plants. [ABSTRACT FROM PUBLISHER]

Prunus cerasus L. is selected tree of genus Prunus susceptible to various pathogens, which caused discoloration, brown spots, blight symptoms and necroses, affecting their aesthetic value. The symptoms of infection observable from spring to autumn are increased, when the plants are in bloom – resulting in dieback and leaf drop. The damage is caused by fungus Coniochaeta prunicola Damm & Crous (Coniochaetales, Sordariomycetes, Ascomycota). The present work tries to specify – on the basis of light-microscopical morphological studies – the fungus C. prunicola that was isolated from Prunus cerasus symptomatic leaves from district Nitra and propose, for the first time, as a causative agent of sour cherry damage. The specific differences in spore size and anamorph morphology to the similar C. velutina could be confirmed. C. prunicola is characterized by dark brown ascomata clothed with setae, the fasciculate, unitunicate, cylindrical asci and broadly almond-shaped, ellipsoidal ascospores with a longitudinal germ slit. [ABSTRACT FROM AUTHOR]

SUMMARY In this study, proteomics and metabolomics were used to study the wheat response to exposure to the SnToxA effector protein secreted by the fungal pathogen Stagonospora nodorum during infection. Ninety-one different acidic and basic proteins and 101 metabolites were differentially abundant when comparing SnToxA- and control-treated wheat leaves during a 72-h time course. Proteins involved in photosynthesis were observed to increase marginally initially after exposure, before decreasing rapidly and significantly. Proteins and metabolites associated with the detoxification of reactive oxygen species in the chloroplast were also differentially abundant during SnToxA exposure, implying that the disruption of photosynthesis causes the rapid accumulation of chloroplastic reactive oxygen species. Metabolite profiling revealed major metabolic perturbations in central carbon metabolism, evidenced by significant increases in tricarboxylic acid (TCA) cycle intermediates, suggestive of an attempt by the plant to generate ATP and reducing equivalents in response to the collapse of photosynthesis caused by SnToxA. This was supported by the observation that the TCA cycle enzyme malate dehydrogenase was up-regulated in response to SnToxA. The infiltration of SnToxA also resulted in a significant increase in abundance of many pathogenicity-related proteins, even in the absence of the pathogen or other pathogen-associated molecular patterns. This approach highlights the complementary nature of proteomics and metabolomics in studying effector-host interactions, and provides further support for the hypothesis that necrotrophic pathogens, such as S. nodorum, appear to exploit existing host cell death mechanisms to promote pathogen growth and cause disease. [ABSTRACT FROM AUTHOR]

Tan spot, caused by Pyrenophora tritici-repentis, is an important disease of wheat worldwide. To manage tan spot, quinone outside inhibitor (QoI) fungicides such as azoxystrobin and pyraclostrobin have been applied in many countries. QoI fungicides target the cytochrome b (cyt b) site in complex III of mitochondria and, thus, pose a serious risk for resistance development. The resistance mechanism to QoI fungicides is mainly due to point mutations in the cyt b gene. The objective of this study was to develop a molecular detection method for the four currently known mutations responsible for shifts in sensitivity toward QoI fungicides in P. tritici-repentis. Twelve specific primers were designed based on sequences from the National Center for Biotechnology Information accessions AAXI01000704 and DQ919068 and used to generate a fragment of the cyt b gene which possesses four known single-nucleotide polymorphisms (SNPs). These mutant clones served as positive controls because QoI-insensitive and -reduced-sensitive isolates of P. tritici-repentis have not yet been reported in the United States. The partial cyt b gene clones were sequenced to identify the SNPs at sites G143A and F129L. Genomic DNA of the mutated partial cyt b gene clones and the European QoI-insensitive and -reduced-sensitive isolates of P. tritici-repentis possessing G143A (GCT) and F129L (TTA, TTG, and CTC) mutations were amplified by polymerase chain reaction (PCR) using two specific primer pairs and were further digested with three specific restriction enzymes (BsaJI, Fnu4HI, and MnlI). The results of the digested PCR product from genomic DNA of known QoI-insensitive and -reduced-sensitive isolates of P. tritici-repentis had DNA bands consistent with the mutation GCT at G143A and the mutations TTA, TTG, and CTC at F129L. The amplified region at the F129 site also had 99% sequence similarity with P. teres, the net blotch pathogen of barley. To validate mutations, we further tested two isolates of P. teres known to have reduced sensitivity to QoI fungicides possessing the mutations TTA and CTC at F129L. After PCR amplification and restriction digestion, DNA bands identical to those observed for the partial cyt b mutant clones were detected. These results suggest that this newly developed two-step molecular detection method is rapid, robust, and specific to monitor QoI-insensitive and -reduced-sensitive isolates of P. tritici-repentis. [ABSTRACT FROM AUTHOR]

Over the past 10 years, rust diseases have become increasingly prevalent on certain cultivars of Kentucky bluegrass. This pattern suggests that new races or new species of rust fungi may have emerged. To test this hypothesis, 66 samples of turfgrass rust fungi collected from across the United States were evaluated based on sequences of the internal transcribed spacer (ITS)-5.8S rDNA region. Phylogenetic analysis revealed three species: Puccinia coronata, P. graminis, and P. striiformis, comprising 67, 28, and 5% of the samples, respectively. P. coronata was frequently found in association with Kentucky bluegrass, a host-pathogen relationship that has not been previously reported. Comparison of molecular analyses with the use of standard field identification techniques-host association and pustule pigmentation-showed that 58% of the Kentucky bluegrass samples would have been incorrectly diagnosed using nonmolecular criteria. To avoid such misidentifications, a real-time polymerase chain reaction diagnostic protocol was developed for turfgrass-associated P. graminis, P. coronata, and P. striiformis using ITS sequences. Accurate, reproducible, species-specific identifications were made using as few as 50 to 150 urediniospores, even in mixed infections. This study represents the first DNA-based evaluation of turfgrass rust fungi and provides a quick and reliable sequence-based protocol as an alternative to less reliable field-based identification techniques. [ABSTRACT FROM AUTHOR]

Contemporary species identification relies strongly on sequence-based identification, yet resources for identification of many fungal and oomycete pathogens are rare. We developed two web-based, searchable databases for rapid identification of Phytophthora spp. based on sequencing of the internal transcribed spacer (ITS) or the cytochrome oxidase (cox) I and 2 spacer region, followed by BLAST searching the databases. Both databases are highly selective. For ITS, only sequences associated with published Phytophthora spp. descriptions or classic Phytophihora phylogenetics references are included. For the cox spacer region, only data obtained by resequencing select isolates reported in published work were included. Novel taxa tentatively named are selectively included in the database and labeled as Phytophthora taxon "X"; as in, for example, P taxon "asparagi". The database was validated with 700 Phytophthora isolates collected from nursery environments during 2006 to 2009. This resource, found at www. Phytophthora-ID.org, is a robust and validated tool for molecular identification of Phytophthora spp. and is regularly being updated. [ABSTRACT FROM AUTHOR]

The article presents an introduction to the issue on the theme of genomics research on rust fungi plant pathogens, including topics such as transcriptome analysis, effector proteins, and genetic aspects of fungal virulence.

In plant innate immunity, the first line of microbial recognition leading to active defence responses relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs). This recognition leads to PAMP-triggered immunity (PTI). Despite the numerous PAMPs recognised by plants, only a handful of PRRs are characterised. For most, they correspond to transmembrane proteins with a ligand-binding ectodomain. PRRs interact with additional transmembrane proteins that act as signalling adapters or amplifiers to achieve full functionality. The crucial role of PRRs in anti-microbial immunity is demonstrated by the direct targeting of PRRs and their associated proteins by pathogenic virulence effectors. [Copyright &y& Elsevier]

Plants have evolved sensory mechanisms to detect pathogen attack and trigger signalling pathways that induce rapid defence responses. These mechanisms include not only direct detection of pathogen-derived elicitors (e.g. pathogen-associated molecular patterns (PAMPs) and avirulence factors or effectors) but also indirect sensing of pathogens’ impact on the host plant. Among the first plant barriers to pathogen ingress are the cell wall and the cuticle. For those pathogens that penetrate the plant cell wall to gain access to water and nutrients of the plant protoplast, small wounds at penetration sites are created by enzymatic or physical disruption of the plant cell wall. Thus, cell wall integrity sensing is one mechanism by which plants may detect pathogen attack. Some plant cell wall fragments, notably oligogalacturonic acids, elicit similar defence responses in plants as the non-specific PAMP elicitors (e.g. production of reactive oxygen species, elevated expression of defence-associated genes), suggesting that PAMP signalling may provide a good model for studying cell wall integrity sensing in plants. However, much remains to be discovered about this sensing mechanism. [Copyright &y& Elsevier]

Skin spot disease of potato caused by the pathogen Polyscytalum pustulans is likely to become more important with the withdrawal of 2-aminobutane as a fungicide, and new methods of control will need to be found. As part of a disease control strategy, it will be necessary to study the disease in more detail, to utilize host resistance and to identify stocks where problems are likely to arise. Existing methods for the detection and quantification of P. pustulans are time-consuming and require specific expertise. Real-time PCR assays have been developed for many pathogens of potato and have subsequently been used as tools for the study of the epidemiology and control of disease. The development of a real-time PCR assay for the detection and quantification of P. pustulans is described. The specificity of the assay was demonstrated and detection was shown to be reliable at levels as low as 20–250 fg/ μl DNA, (equivalent to 60–680 pg DNA/g) in soil and on symptomless tubers at attogram (ag) levels. These values are in line with previously developed tests. [ABSTRACT FROM AUTHOR]

Phytophthora sojae Kauf. and Gerd, a host specific pathogen to soybean, causes pre and postemergence damping-off and root and stem rot on soybean. The pathogen evokes severe yield losses in most soybean growing areas worldwide. The objective of this study was to determine phenotypic and genotypic diversity among single zoospore isolates (SZIs) originating from two single zoosporangia (Ps411-1 and Ps411-2) derived from the same parental isolate of P. sojae Ps411. Results showed that colony morphology and growth rate of 32 SZIs derived from sporangium Ps411-1 and 35 SZIs released from sporangium Ps411-2 did not significantly differ from the parental isolate Ps411. Pathogenicity of the SZIs was tested on three resistant and three susceptible Chinese soybean cultivars. While the majority of SZIs derived from sporangium Ps411-1(59.4%) and sporangium Ps411-2(71.4%) retained the same virulence spectrum as the parental isolate, the other SZIs of both progenies demonstrated either a higher or a lower level of virulence compared to that of parental isolate. A low level genetic variability in the populations of both single zoospore progenies was also demonstrated using the sequence-related amplified polymorphism (SRAP) technique. Cluster analysis separated the SZIs from both zoosporangia, Ps411-1 and Ps411-2, into four and three SRAP groups, respectively. No close correlation among SRAP and virulence could be established among SZIs. The results of this study suggest that virulence variability may be regarded as part of the total genetic changes among the zoospore progenies derived from single-zoosporangia. The pathogenic variability during asexual reproduction may play a role in changing the virulence structure of P. sojae. [ABSTRACT FROM AUTHOR]

Abstract: Camalexin, the major Arabidopsis phytoalexin, is synthesized in response to a great variety of pathogens. Specific pathogen-associated molecular patterns, such as Nep1-like proteins from oomycetes act as signals triggering the transcriptional activation of the camalexin biosynthetic genes. PaNie, a Nep1-like protein from Pythium aphanidermatum was expressed in Arabidopsis under the control of an ethanol-inducible promoter. This system was developed as a tool to study the regulation of camalexin biosynthesis. It allowed induction of camalexin preceded by strong transcriptional activation of the tryptophan and camalexin biosynthetic genes. In flowers and green siliques PaNie expression elicited only minor camalexin formation, indicating low capability for phytoalexin synthesis in reproductive organs in contrast to leaf and stem tissue. [Copyright &y& Elsevier]

Abstract: Plant pathogens secrete effector molecules that contribute to the establishment of disease in their plant hosts. The identification of cellular cues that regulate effector gene expression is an important aspect of understanding the infection process. Nutritional status in the cell has been postulated to be a cue for effector gene expression. Several studies have shown the induction of the same effector genes during growth under nitrogen-starved conditions in vitro as during growth in planta, suggesting that a nitrogen-poor environment exists during colonization. As a consequence, it has been proposed that growth in nitrogen-starved media mimics the environment that a pathogen encounters during growth in planta. Although this relationship has been implied in several studies, there is little known regarding available nitrogen during colonization for fungal pathogens. This review focuses on the effect of nitrogen starvation on fungal effector gene expression and examines the role of fungal nitrogen regulatory genes to help gain an understanding of whether nitrogen availability within the host is an important factor in disease development. [Copyright &y& Elsevier]

Focuses on the molecular and morphological characteristics of the causal agent of black knot in Prunus, Apiosporina morbosa. Similarities of the overall colony and conidial morphology in cultures of the A. morbosa isolates with an isolate of Cladosporium herbarum; Genetic features of A. morbosa.

The hrp genes of the plant pathogen Ralstonia solanacearum are key pathogenicity determinants; they encode a type III protein secretion machinery involved in the secretion of mediators of the bacterium-plant interaction. These hrp genes are under the genetic control of the hrpB regulatory gene, expression of which is induced when bacteria are co-cultivated with plant cell suspensions. In this study, we used hrp-gfp transcriptional fusions to demonstrate that the expression of the hrpB and type III secretion genes is specifically induced in response to the bacterium-plant cell contact. This contact-dependent induction of hrpB gene expression requires the outer membrane protein PrhA, but not a functional type III secretion apparatus. Genetic evidence indicates that PrhA constitutes the first example of a bacterial receptor for a non-diffusible signal present in the plant cell wall and which triggers the transcriptional activation of bacterial virulence genes. [ABSTRACT FROM AUTHOR]

Examines the involvement of novel genes in regulating the pathogenicity factor production in gene clusters of Xanthomonas campestris pathovar campestris (Xcc). Identification of orf4 and rpfE at the right-hand section of Xcc DNA fragment clone; Effect of novel gene mutations on extracellular enzyme production; Role of pathogenesis in plant genetics.

Reports on the presence of a novel Ac-like transposon of Arabidopsis that is related to a deletion of the RPS5 disease resistance gene. Loss of RPS5 caused by double-strand break and subsequent repair; Unequal crossing between resistance gene homologs; Separation of RPS5 and RFL1 disease resistance genes by 1.4 kb.

Reports on the complete chemical structure elucidation of a host-selective chemical signal produced by the blackleg fungus. Synthesis of a new metabolite, phomalide(1) by germinated spores; Inhibition of synthesis by sirodesmin; Discovery of five discrete spin-coupled systems.

The article discusses research on the molecular mechanisms behind disease resistance in wheat, which is the second-most-produced cereal crop in the world. This knowledge has allowed for the development of crop varieties that resist common diseases and for specific plant recognition of a pathogen gene product that yields resistance to related pathogens. These researchers describe the process of cloning wheat to be resistant to multiple rusts. Specific genes and pleiotropic drug resistance transporters are discussed in this study, providing some of the earliest information on quantitative resistance.

The article discusses a plant sciences study by Taylor and colleagues in a 2012 issue of "PloS Pathology" magazine investigating how the interaction of the XopN protein effector with the 14-3-3 protein TFT1 modulates a plant's pathogen defense response.