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Anthracnose, caused by the fungus Colletotrichum lindemuthianum, poses a significant and widespread threat to the common bean crop. The use of plant genetic resistance has proven to be the most effective strategy for managing anthracnose disease. The Amendoim Cavalo (AC) Andean cultivar has resistance against multiple races of C. lindemuthianum, which is conferred by the Co-AC gene. Fine mapping of this resistance gene to common bean chromosome Pv01 enabled the identification of Phvul.001G244300, Phvul.001G244400, and Phvul.001G244500 candidate genes for further validation. In this study, the relative expression of Co-AC candidate genes was assessed, as well as other putative genes in the vicinity of this locus and known resistance genes, in the AC cultivar following inoculation with the race 73 of C. lindemuthianum. Gene expression analysis revealed significantly higher expression levels of Phvul.001G244500. Notably, Phvul.001G244500 encodes a putative Basic Helix–Loop–Helix transcription factor, suggesting its involvement in the regulation of defense responses. Furthermore, a significant modulation of the expression of defense-related genes PR1a, PR1b, and PR2 was observed in a time-course experiment. These findings contribute to the development of improved strategies for breeding anthracnose-resistant common bean cultivars, thereby mitigating the impact of this pathogen on crop yields and ensuring sustainable bean production. [ABSTRACT FROM AUTHOR]

Olive anthracnose is the most important fungal disease of the olive fruit worldwide, with the fungus Colletotrichum acutatum as the main cause of the disease in Greece. A total of 11 commercial biological plant protection products (bioPPPs) (Amylo-X®, Botector®, FytoSave®, LBG 01F34®, Mevalone®, Polyversum®, Remedier®, Serenade® ASO, Sonata®, Trianum-P®, Vacciplant®), with various modes of action against the fungus C. acutatum, were evaluated by bioassays using detached fruits of two important olive Greek varieties, cv. Koroneiki and cv. Kalamon. Subsequently, the most effective bioPPPs were evaluated for their ability to induce plant defense mechanisms, by determining the expression levels of ten Olea europaea defense genes (Pal, CuaO, Aldh1, Bglu, Mpol, Lox, Phely, CHI-2, PR-10, PR-5). Remedier®, Trianum-P®, Serenade® ASO, Sonata®, and Mevalone® were the most effective in reducing disease severity, and/or inhibiting the conidia production by the fungus at high rates. Post bioPPPs application, high expression levels of several olive plant defense genes were observed. This study provides insights into commercial bioPPPs' effectiveness in controlling olive anthracnose, as well as biocontrol-agents-mediated modulation of olive defense mechanisms. [ABSTRACT FROM AUTHOR]

Anthracnose (ANT) and angular leaf spot (ALS) are significant diseases in common bean, leading to considerable yield losses under specific environmental conditions. The California Dark Red Kidney (CDRK) bean cultivar is known for its resistance to multiple races of both pathogens. Previous studies have identified the CoPv01CDRK/PhgPv01CDRK resistance loci on chromosome Pv01. Here, we evaluated the expression levels of ten candidate genes near the CoPv01CDRK/PhgPv01CDRK loci and plant defense genes using quantitative real-time PCR in CDRK cultivar inoculated with races 73 of Colletotrichum lindemuthianum and 63-39 of Pseudocercospora griseola. Gene expression analysis revealed that the Phvul.001G246300 gene exhibited the most elevated levels, showing remarkable 7.8-fold and 8.5-fold increases for ANT and ALS, respectively. The Phvul.001G246300 gene encodes an abscisic acid (ABA) receptor with pyrabactin resistance, PYR1-like (PYL) protein, which plays a central role in the crosstalk between ABA and jasmonic acid responses. Interestingly, our results also showed that the other defense genes were initially activated. These findings provide critical insights into the molecular mechanisms underlying plant defense against these diseases and could contribute to the development of more effective disease management strategies in the future. [ABSTRACT FROM AUTHOR]

Bacterial wilt disease caused by Ralstonia solanacearum impacts negatively on potato production. This study evaluated the effects of thymol and eugenol encapsulated in chitosan nanoparticles (TCNP and ECNP) on the virulence genes (PhcA, XpsR and HrpG) of R. solanacearum and their in vivo efficacy against bacterial wilt. Gene expression levels of virulence genes in the presence of TCNP (5.6 and 11.3 µg mL−1) and ECNP (11.3 and 22.5 µg mL−1) together with those of plant defense genes (chitinase and β-l,3-glucanase) were determined through RT-qPCR. All the virulence genes were downregulated when exposed to both TCNP and ECNP while glucanase and chitinase genes increased and peaked after 18 hours post inoculation. The lowest disease severity index (10.3%) was recorded with plants treated with 90 µg mL−1 ECNP. The results of this study show that both TCNP and ECNP have a potential to be used as bacterial wilt bactericides. [ABSTRACT FROM AUTHOR]

Among other environmental factors, phytopathogens have key roles in limiting global crop production. While an in-depth understanding of plant-pathogen interactions is therefore necessary to develop sustainable crop protection strategies, the genetic basis of plant-pathogen interactions is poorly understood. In this study, we tested the growth and resistance of an important phytopathogen, Pseudomonas syringae pv tomato DC3000 ( Pst DC3000), in 80 gene knockouts, identified previously through genome-wide association mapping of global Arabidopsis thaliana populations. Amongst these, most of the genes are previously known to regulate multiple functions in plants including cellular mechanisms, growth, reproduction, hormonal signaling, and tolerance to both biotic and abiotic stresses (extreme temperature, drought, salinity, pollutants, and nutrient stresses, etc.). The Pst DC3000 demonstrated two distinct growth patterns in all gene knockouts, showing maximum growth after 4 or 7 days of inoculation (DOI). Mostly, the wild-type ( Col-0) demonstrated higher phytopathogen growth than almost all gene knockouts after 4 or 7 DOI. The differential abundance of Pst DC3000 in the multiple gene knockouts reveals a number of new genes important for plant defense. Meanwhile, our results and a review of previous literature suggest interaction of plant defense with plant growth, reproduction, hormonal and abiotic stress tolerance. Thus in future studies, a mechanistic understanding of the genetic, ecological and physiological basis of plant-pathogen interactions, and pleiotropic interactions may prove instrumental in developing sustainable plant protection practices. [ABSTRACT FROM AUTHOR]

The role of ethylene on arbuscular mycorrhiza (AM) development remains unclear. We used tomato ethylene mutants in near isogenic genotypes to evaluate AM development and growth differences and whether changes in levels of plant defense-related transcripts in roots were correlated with those differences. The cultivar Micro-Tom (MT) and mutants overproducing ethylene ( epinastic, epi) and insensitive to ethylene ( Never-ripe, Nr) were inoculated with Glomus clarum. The epi mutants exhibited reduced intraradical colonization at all time-points and reduced frequencies of hyphopodia and arbuscules at 30 and 37 days after inoculation (DAI) compared to MT. At these times and 23 DAI, epi roots contained higher levels of mRNAs encoding Chi3 and Chi9 chitinases, Cu-Zn superoxide dismutase, catalase and a peroxidase than MT roots. In contrast, Nr showed higher intraradical colonization and frequencies of arbuscules, external hypha and hyphopodia but only at 23 DAI. At the preceding 16 DAI time point, levels of antioxidant enzyme mRNAs were higher while Chi3, Chi9 and GlucB mRNAs were lower than in MT roots. Our study provides evidence that specific stages of AM development were altered negatively in epi and positively in Nr. These effects on fungal growth are most likely due to altered ethylene signaling modulating the plant defense system. [ABSTRACT FROM AUTHOR]

Background: Anthracnose of lentil, caused by the hemibiotrophic fungal pathogen Colletotrichum truncatum is a serious threat to lentil production in western Canada. Colletotrichum truncatum employs a bi-phasic infection strategy characterized by initial symptomless biotrophic and subsequent destructive necrotrophic colonization of its host. The transition from biotrophy to necrotrophy (known as the biotrophy-necrotrophy switch [BNS]) is critical in anthracnose development. Understanding plant responses during the BNS is the key to designing a strategy for incorporating resistance against hemibiotrophic pathogens either via introgression of resistance genes or quantitative trait loci contributing to host defense into elite cultivars, or via incorporation of resistance by biotechnological means. Results: The in planta BNS of C. truncatum was determined by histochemical analysis of infected lentil leaf tissues in time-course experiments. A total of 2852 lentil expressed sequence tags (ESTs) derived from C. truncatum-infected leaf tissues were analyzed to catalogue defense related genes. These ESTs could be assembled into 1682 unigenes. Of these, 101 unigenes encoded membrane and transport associated proteins, 159 encoded proteins implicated in signal transduction and 387 were predicted to be stress and defense related proteins (GenBank accessions: JG293480 to JG293479). The most abundant class of defense related proteins contained pathogenesis related proteins (encoded by 125 ESTs) followed by heat shock proteins, glutathione S-transferase, protein kinases, protein phosphatase, zinc finger proteins, peroxidase, GTP binding proteins, resistance proteins and syringolide-induced proteins. Quantitative RT-PCR was conducted to compare the expression of two resistance genes of the NBS-LRR class in susceptible and partially resistant genotypes. One (contig186) was induced 6 days post-inoculation (dpi) in a susceptible host genotype (Eston) whereas the mRNA level of another ( LT21-1990) peaked 4 dpi in a partially resistant host genotype (Robin), suggesting roles in conditioning the susceptibility and conferring tolerance to the pathogen, respectively. Conclusions: Data obtained in this study suggest that lentil cells recognize C. truncatum at the BNS and in response, mount an inducible defense as evident by a high number of transcripts (23% of the total pathogen-responsive lentil transcriptome) encoding defense related proteins. Temporal expression polymorphism of defense related genes could be used to distinguish the response of a lentil genotype as susceptible or resistant. [ABSTRACT FROM AUTHOR]

The STH-2 gene is rapidly activated in potato leaves and tubers following elicitation or infection by Phytophthora infestans. However, its biochemical function remains unknown. In order to ascertain if STH-2 protein is directly involved in the defense of potato against pathogens, the STH-2 coding sequence under the control of the CaMV 35S promoter was introduced into potato plants. Transgenic plants expressing the STH-2 gene were analyzed for an altered pattern of susceptibility to a compatible race of P. infestans and to potato virus X. Results indicate that constitutive expression of the STH-2 gene did not reduce susceptibility of potato to these pathogens. [ABSTRACT FROM AUTHOR]

Endochitinases (E.C. 3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen. [ABSTRACT FROM AUTHOR]

Glucan endo-1,3-β-glucosidases (β-1,3-glucanases) have been implicated in several developmental processes and they may also play a direct role in the plant's defense against fungal pathogens. In an effort to characterize the glucanase gene family, complementary DNA clones encoding an acidic form of β-1,3-glucanase have been isolated from tobacco. The cDNA was expressed in E. coli and shown to encode a β-1,3-glucanase activity. The protein sequence encoded by the cDNA was found to match the partial protein sequence of PR-35, a previously characterized β-1,3-glucanase [29]. The protein encoded by the cDNA was purified from the extracellular fluid of TMV-infected tobacco leaves and found by immunological methods to correspond to glucanase PR-Q' [10]. From a detailed analysis of the cDNA it is clear that this glucanase represents a third structural class of enzyme which differs substantially from both the basic, vacuolar glucanase and the acidic, extracellular forms (PR-2, PR-N and PR-O). It has previously been demonstrated that the basic form of β-1,3-glucanase is synthesized as a pre-pro-enzyme and upon maturation the 21 amino acid signal peptide and a 22 amino acid carboxy-terminal peptide are removed. This processing event has been proposed to be involved with the vacuolar localization of the enzyme. By comparing the deduced protein structure of PR-Q' to that of the basic form it is evident that this extracellular enzyme is missing the carboxy-terminal 22 amino acids. The role of a conserved phenylalanine-glycine dipeptide in the processing of glucanases and other pathogenesis-related proteins from tobacco is discussed. [ABSTRACT FROM AUTHOR]

Protective transgenes introduced into plants can be classified as directed against insects, fungi, bacteria or viruses. Mechanisms by which they protect plants in some cases are relatively simple and understood while in most cases they present only the field of rapidly progressing investigations. A brief review of the recent concepts of the resistance induced in plants against viruses by virus-derived transgenes is presented with emphasising the RNA mediated resistance. The RNA mediated resistance seems to operate in Nicotiana benthamiana plants transformed in our laboratory with cDNA of the PPV CP gene: both translatable and untranslatable versions of the cDNA made the transformed plants resistant against PPV. The resistant plants contained more than one copy of the transgene. To protect against insects plants were in our laboratory transformed with potato proteinase inhibitor II gene (PPI-II). The PPI-II gene expressed in model plants inhibited trypsin activity to an expected level. [ABSTRACT FROM AUTHOR]