Browsing by Author "Ghosh, Srayan"

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Bacteria-fungal confrontation and fungal growth prevention assay
(Bio-protocol LLC., 2018) Kumar, Rahul; Swain, Durga Madhab; Yadav, Sunil Kumar; Tyagi, Isha; Kumar, Rajeev; Das, Joyati; Ghosh, Srayan; Jha, Gopaljee
There are some bacteria which can grow and multiply at the cost of living fungal biomass. They can potentially utilize fungi as a source of nutrients to forage over them. Such phenomenon is known as bacterial mycophagy, however, its mechanistic insights need to be explored to identify the molecules involved in mycophagy for potential utilization in controlling various fungal diseases. Recently we have demonstrated that a rice-associated bacteria Burkholderia gladioli strain NGJ1 exhibits mycophagous ability on several fungi, including Rhizoctonia solani, the necrotrophic fungal pathogen causing sheath blight disease in rice. We hereby describe our validated and efficient methods used to study B. gladioli strain NGJ1-R. solani interactions. These methodologies would be useful for designing assays to study the confrontation between bacteria and fungi which in turn enable discovery of novel antifungal molecules from such bacteria.
Concurrent overexpression of rice G-protein β and γ subunits provide enhanced tolerance to sheath blight disease and abiotic stress in rice
(Springer Nature Publishing AG, 2019) Swain, Durga Madhab; Sahoo, Ranjan Kumar; Chandan, Ravindra Kumar; Ghosh, Srayan; Kumar, Rahul; Jha, Gopaljee; Tuteja, Narendra
The heterotrimeric G-proteins act as signalling molecules and modulate various cellular responses including stress tolerance in eukaryotes. The gamma (γ) subunit of rice G-protein (RGG1) was earlier reported to promote salinity stress tolerance in rice. In the present study, we report that a rice gene-encoding beta (β) subunit of G-protein (RGB1) gets upregulated during both biotic (upon a necrotrophic fungal pathogen, Rhizoctonia solani infection) and drought stresses. Markerfree transgenic IR64 rice lines that simultaneously overexpress both RGB1 and RGG1 genes under CaMV35S promoter were raised. The overexpressing (OE) lines showed enhanced tolerance to R. solani infection and salinity/drought stresses. Several defense marker genes including OsMPK3 were signifcantly upregulated in the R. solani-infected OE lines. We also found the antioxidant machineries to be upregulated during salinity as well as drought stress in the OE lines. Overall, the present study provides evidence that concurrent overexpression of G-protein subunits (RGG1 and RGB1) impart multiple (both biotic and abiotic) stress tolerance in rice which could be due to the enhanced expression of stress-marker genes and better management of reactive oxygen species (ROS)-scavenging/photosynthetic machinery. The current study suggests an improved approach for simultaneous improvement of biotic and abiotic stress tolerance in rice which remains a major challenge for its sustainable cultivation.
Draft genome sequence of broad-spectrum antifungal bacterium Burkholderia gladioli strain NGJ1, isolated from healthy rice seeds
(American Society for Microbiology, 2015) Jha, Gopaljee; Tyagi, Isha; Kumar, Rajeev; Ghosh, Srayan
We report here the draft genome sequence of Burkholderia gladioli strain NGJ1. The strain was isolated from healthy rice seeds and exhibits broad-spectrum antifungal activity against several agriculturally important pathogens, including Rhizoctonia solani, Magnaporthe oryzae, Venturia inaequalis, and Fusarium oxysporum.
Editorial: Utilization of microbiome to develop disease resistance in crop plants against phytopathogens
(Frontiers Media S.A., 2023) Ghosh, Srayan; Jha, Gopaljee
Sustainable agriculture is important for ensuring food security at an affordable cost. Agricultural practices heavily depend on agrochemicals, such as fertilizers, fungicides, and pesticides, to ensure optimal productivity and prevent losses due to pathogens and pests. However, with time, it has become clear that most commonly used agrochemicals have residual side effects on consumers, soil health, and the environment. Hence, developing newer environmentally friendly approaches to ensure crop productivity, with minimal usage of agrochemicals, is highly desirable. The potential of plant/rhizospheric soilassociated microbes to support the overall growth of plants and provide protection against phytopathogens has been actively studied in recent years.
Enzymatic and non-enzymatic functional attributes of plant microbiome
(Elsevier B.V., 2021) Das, Joyati; Yadav, Sunil Kumar; Ghosh, Srayan; Tyagi, Kriti; Magotra, Ankita; Krishnan, Aiswarya; Jha, Gopaljee
Microbiome plays an important role in plant growth and adaptation to various environmental conditions. The cross-talk between host plant and microbes (including microbe-microbe interactions) plays a crucial role in shaping the microbiome. Recent studies have highlighted that plant microbiome is enriched in genes encoding enzymes and natural products. Several novel antimicrobial compounds, bioactive natural products and lytic/degrading enzymes with industrial implications are being identified from the microbiome. Moreover, advancements in metagenomics and culture techniques are facilitating the development of synthetic microbial communities to promote sustainable agriculture. We discuss the recent advancements, opportunities and challenges in harnessing the full potential of plant microbiome.
Evolution of pathogenicity-associated genes in Rhizoctonia solani AG1-IA by genome duplication and transposon-mediated gene function alterations
(BioMed Central Ltd, 2023) Francis, Aleena; Ghosh, Srayan; Tyagi, Kriti; Prakasam, V.; Rani, Mamta; Singh, Nagendra Pratap; Pradhan, Amrita; Sundaram, R. M.; Priyanka, C.; Laha, G. S.; Kannan, C.; Prasad, M. S.; Chattopadhyay, Debasis; Jha, Gopaljee
Background: Rhizoctonia solani is a polyphagous fungal pathogen that causes diseases in crops. The fungal strains are classified into anastomosis groups (AGs); however, genomic complexity, diversification into the AGs and the evolution of pathogenicity-associated genes remain poorly understood. Results: We report a recent whole-genome duplication and sequential segmental duplications in AG1-IA strains of R. solani. Transposable element (TE) clusters have caused loss of synteny in the duplicated blocks and introduced differential structural alterations in the functional domains of several pathogenicity-associated paralogous gene pairs. We demonstrate that the TE-mediated structural variations in a glycosyl hydrolase domain and a GMC oxidoreductase domain in two paralogous pairs affect the pathogenicity of R. solani. Furthermore, to investigate the association of TEs with the natural selection and evolution of pathogenicity, we sequenced the genomes of forty-two rice field isolates of R. solani AG1-IA. The genomic regions with high population mutation rates and with the lowest nucleotide diversity are enriched with TEs. Genetic diversity analysis predicted the genes that are most likely under diversifying and purifying selections. We present evidence that a smaller variant of a glucosamine phosphate N-acetyltransferase (GNAT) protein, predicted to be under purifying selection, and an LPMP_AA9 domain-containing protein, predicted to be under diversifying selection, are important for the successful pathogenesis of R. solani in rice as well as tomato. Conclusions: Our study has unravelled whole-genome duplication, TE-mediated neofunctionalization of genes and evolution of pathogenicity traits in R. solani AG1-IA. The pathogenicity-associated genes identified during the study can serve as novel targets for disease control.
Fungal effectors, the double edge sword of phytopathogens
(Springer Nature Publishing AG, 2021) Pradhan, Amrita; Ghosh, Srayan; Sahoo, Debashis; Jha, Gopaljee
Phyto-pathogenic fungi can cause huge damage to crop production. During millions of years of coexistence, fungi have evolved diverse life-style to obtain nutrients from the host and to colonize upon them. They deploy various proteinaceous as well as non-proteinaceous secreted molecules commonly referred as efectors to sabotage host machinery during the infection process. The efectors are important virulence determinants of pathogenic fungi and play important role in successful pathogenesis, predominantly by avoiding host-surveillance system. However, besides being important for pathogenesis, the fungal efectors end-up being recognized by the resistant cultivars of the host, which mount a strong immune response to ward-of pathogens. Various recent studies involving diferent pathosystem have revealed the virulence/avirulence functions of fungal efectors and their involvement in governing the outcome of host–pathogen interactions. However, the efectors and their cognate resistance gene in the host remain elusive for several economically important fungal pathogens. In this review, using examples from some of the biotrophic, hemi-biotrophic and necrotrophic pathogens, we elaborate the double-edged functions of fungal efectors. We emphasize that knowledge of efector functions can be helpful in efective management of fungal diseases in crop plants.
Genome analysis provides insight about pathogenesis of Indian strains of Rhizoctonia solani in rice
(Springer Nature Publishing AG, 2019) Ghosh, Srayan; Mirza, Neelofar; Kanwar, Poonam; Tyagi, Kriti; Jha, Gopaljee
The Rhizoctonia solani species complex is comprised of strains belonging to different anastomosis groups and causes diseases in several economically important crops, including rice. However, individuals within same anastomosis group exhibit distinct morphological and pathological differences on the same host. In this study, we have sequenced the genome of two aggressive Indian strains (BRS11 and BRS13) belonging to AG1-IA anastomosis group and compared them with the available genome of R. solani AG1-IA. We identified several SNPs and Indels in both of these genomes, in comparison to the AG1-IA genome. Furthermore, we observed expansion and emergence of orthogroups in these Indian strains and identified those potentially associated with pathogenesis. Amongst them, transposable elements, cell wall degrading enzymes, transcription factors, and oxalate decarboxylase were noteworthy. The current study unravels genetic variations and identifies genes that might account for pathogenicity variations amongst R. solani strains.
Host alternative NADH:ubiquinone oxidoreductase serves as susceptibility factor to promote pathogenesis of Rhizoctonia solani in plants
(American Phytopathological Society, 2019) Kant, Ravi; Tyagi, Kriti; Ghosh, Srayan; Jha, Gopaljee
Phytopathogens have evolved mechanisms to utilize host genes (commonly known as susceptibility factors) to promote its pathogenesis. Rhizoctonia solani is one of the highly destructive fungal pathogens of various plants, including rice. Previously we had reported differentially regulated rice genes during pathogenesis of R. solani. In this study, we analyzed the role of tomato homologs of two of the rice genes i.e Isoflavone reductase (IFR) and alternative NADH:ubiquinone oxidoreductase (NUOR) as potential susceptibility factors for R. solani. Virus induced gene silencing (VIGS) of NUOR gene in tomato resulted in compromised susceptibility against R. solani, while IFR-silenced plants demonstrated susceptibility similar to that of control plants. NUOR silencing in tomato led to homogenous accumulation of reactive oxygen species (ROS) (optimum range) upon R. solani infection. In addition, expression and enzyme activities of some of the host defense and anti-oxidant genes were enhanced, while H2O2 content, lipid peroxidation and electrolyte leakage were reduced in NUOR-silenced plants. Similarly, transient silencing of OsNUOR gene provided tolerance against R. solani infection in rice. Overall, the data presented in this study suggests that NUOR serves as a host susceptibility factor to promote pathogenesis of R. solani.
The host and pathogen myo-inositol-1-phosphate synthases are required for Rhizoctonia solani AG1-IA infection in tomato
(John Wiley & Sons, 2024) Tyagi, Kriti; Chandan, Ravindra K.; Sahoo, Debashis; Ghosh, Srayan; Gupta, Santosh Kumar; Jha, Gopaljee
The myo-inositol-1-phosphate synthase (MIPS) catalyses the biosynthesis of myo-inositol, an important sugar that regulates various physiological and biochemical processes in plants. Here, we provide evidence that host (SlMIPS1) and pathogen (Rs_MIPS) myo-inositol-1-phosphate synthase (MIPS) genes are required for successful infection of Rhizoctonia solani, a devastating necrotrophic fungal pathogen, in tomato. Silencing of either SlMIPS1 or Rs_MIPS prevented disease, whereas an exogenous spray of myo-inositol enhanced disease severity. SlMIPS1 was upregulated upon R. solani infection, and potentially promoted source-to-sink transition, induced SWEET gene expression, and facilitated sugar availability in the infected tissues. In addition, salicylic acid (SA)-jasmonic acid homeostasis was altered and SA-mediated defence was suppressed; therefore, disease was promoted. On the other hand, silencing of SlMIPS1 limited sugar availability and induced SA-mediated defence to prevent R. solani infection. Virus-induced gene silencing of NPR1, a key gene in SA signalling, rendered SlMIPS1-silenced tomato lines susceptible to infection. These analyses suggest that induction of SA-mediated defence imparts disease tolerance in SlMIPS1-silenced tomato lines. In addition, we present evidence that SlMIPS1 and SA negatively regulate each other to modulate the defence response. SA treatment reduced SlMIPS1 expression and myo-inositol content in tomato, whereas myo-inositol treatment prevented SA-mediated defence. We emphasize that downregulation of host/pathogen MIPS can be an important strategy for controlling diseases caused by R. solani in agriculturally important crops.
Identification and functional analysis of AG1-IA specific genes of Rhizoctonia solani
(Springer, 2014) Ghosh, Srayan; Gupta, Santosh Kumar; Jha, Gopaljee
Rhizoctonia solani is an important necrotrophic fungal pathogen which causes disease on diverse plant species. It has been classified into 14 genetically distinct anastomosis groups (AGs), however, very little is known about their genomic diversity. AG1-IA causes sheath blight disease in rice and controlling this disease remains a challenge for sustainable rice cultivation. Recently the draft genome sequences of AG1-IA (rice isolate) and AG1-IB (lettuce isolate) had become publicly available. In this study, using comparative genomics, we report identification of 3,942 R. solani genes that are uniquely present in AG1-IA. Many of these genes encode important biological, molecular functions and exhibit dynamic expression during in-planta growth of the pathogen in rice. Based upon sequence similarity with genes that are required for plant and human/zoonotic diseases, we identified several putative virulence/pathogenicity determinants amongst AG1-IA specific genes. While studying the expression of 19 randomly selected genes, we identified three genes highly up-regulated during in-planta growth. The detailed in silico characterization of these genes and extent of their up-regulation in different rice genotypes, having variable degree of disease susceptibility, suggests their importance in rice-Rhizoctonia interactions. In summary, the present study reports identification, functional characterization of AG1-IA specific genes and predicts important virulence determinants that might enable the pathogen to grow inside hostile plant environment. Further characterization of these genes would shed useful insights about the pathogenicity mechanism of AG1-IA on rice.
Identification of candidate pathogenicity determinants of Rhizoctonia solani AG1-IA, which causes sheath blight disease in rice
(Springer Nature, 2018) Ghosh, Srayan; Kanwar, Poonam; Jha, Gopaljee
Sheath blight disease is one of the predominant diseases of rice and it is caused by the necrotrophic fungal pathogen Rhizoctonia solani. The mechanistic insight about its widespread success as a broad host range pathogen is limited. In this study, we endeavor to identify pathogenicity determinants of R. solani during infection process in rice. Through RNAseq analysis, we identified a total of 65 and 232 R. solani (strain BRS1) genes to be commonly upregulated in three different rice genotypes (PB1, Tetep, and TP309) at establishment and necrotrophic phase, respectively. The induction of genes encoding extracellular protease, ABC transporter, and transcription factors were notable during establishment phase. While during necrotrophic phase, several CAZymes, sugar transporters, cellular metabolism, and protein degradation-related genes were prominently induced. We have also identified few putative secreted effector encoding genes that were upregulated during pathogenesis. The qPCR analysis further validated the phase-specific expression dynamics of some selected putative effectors and pathogenicity-associated genes. Overall, the present study reports identification of key genes and processes that might be crucial for R. solani pathogenesis. The ability to effectively damage host cell wall and survive in hostile plant environment by managing oxidative stress, cytotoxic compounds, etc. is being proposed to be important for pathogenesis of R. solani in rice. The functional characterization of these genes would provide key insights about this important pathosystem and facilitate development of strategies to control this devastating disease.
Immunity proteins of dual nuclease T6SS effectors function as transcriptional repressors
(EMBO Press, 2021) Yadav, Sunil Kumar; Magotra, Ankita; Ghosh, Srayan; Krishnan, Aiswarya; Pradhan, Amrita; Kumar, Rahul; Das, Joyati; Sharma, Mamta; Jha, Gopaljee
Bacteria utilize type VI secretion system (T6SS) to deliver antibacterial toxins to target co-habiting bacteria. Here, we report that Burkholderia gladioli strain NGJ1 deploys certain T6SS effectors (TseTBg), having both DNase and RNase activities to kill target bacteria. RNase activity is prominent on NGJ1 as well as other bacterial RNA while DNase activity is pertinent to only other bacteria. The associated immunity (TsiTBg) proteins harbor noncanonical helix–turn–helix motifs and demonstrate transcriptional repression activity, similar to the antitoxins of type II toxin– antitoxin (TA) systems. Genome analysis reveals that homologs of TseTBg are either encoded as TA or T6SS effectors in diverse bacteria. Our results indicate that a new ORF (encoding a hypothetical protein) has evolved as a result of operonic fusion of TA type TseTBg homolog with certain T6SS-related genes by the action of IS3 transposable elements. This has potentially led to the conversion of a TA into T6SS effector in Burkholderia. Our study exemplifies that bacteria can recruit toxins of TA systems as T6SS weapons to diversify its arsenal to dominate during inter-bacterial competitions.
Methionine biosynthetic genes and methionine sulfoxide reductase A are required for Rhizoctonia solani AG1-IA to cause sheath blight disease in rice
(John Wiley & Sons, 2024) Das, Joyati; Ghosh, Srayan; Tyagi, Kriti; Sahoo, Debashis; Jha, Gopaljee
Rhizoctonia solani is a polyphagous necrotrophic fungal pathogen that causes sheath blight disease in rice. It deploys effector molecules as well as carbohydrate-active enzymes and enhances the production of reactive oxygen species for killing host tissues. Understanding R. solani ability to sustain growth under an oxidative-stress-enriched environment is important for developing disease control strategies. Here, we demonstrate that R. solani upregulates methionine biosynthetic genes, including Rs_MET13 during infection in rice, and double-stranded RNA-mediated silencing of these genes impairs the pathogen's ability to cause disease. Exogenous treatment with methionine restores the disease-causing ability of Rs_MET13-silenced R. solani and facilitates its growth on 10 mM H2O2-containing minimal-media. Notably, the Rs_MsrA gene that encodes methionine sulfoxide reductase A, an antioxidant enzyme involved in the repair of oxidative damage of methionine, is upregulated upon H2O2 treatment and also during infection in rice. Rs_MsrA-silenced R. solani is unable to cause disease, suggesting that it is important for the repair of oxidative damage in methionine during host colonization. We propose that spray-induced gene silencing of Rs_MsrA and designing of antagonistic molecules that block MsrA activity can be exploited as a drug target for effective control of sheath blight disease in rice.
A prophage tail-like protein is deployed by Burkholderia bacteria to feed on fungi
(Nature Publishing Group, 2017) Swain, Durga Madhab; Yadav, Sunil Kumar; Tyagi, Isha; Kumar, Rahul; Kumar, Rajeev; Ghosh, Srayan; Das, Joyati; Jha, Gopaljee
Some bacteria can feed on fungi, a phenomenon known as mycophagy. Here we show that a prophage tail-like protein (Bg_9562) is essential for mycophagy in Burkholderia gladioli strain NGJ1. The purified protein causes hyphal disintegration and inhibits growth of several fungal species. Disruption of the Bg_9562 gene abolishes mycophagy. Bg_9562 is a potential effector secreted by a type III secretion system (T3SS) and is translocated into fungal mycelia during confrontation. Heterologous expression of Bg_9562 in another bacterial species, Ralstonia solanacearum, confers mycophagous ability in a T3SS-dependent manner. We propose that the ability to feed on fungi conferred by Bg_9562 may help the bacteria to survive in certain ecological niches. Furthermore, considering its broad-spectrum antifungal activity, the protein may be potentially useful in biotechnological applications to control fungal diseases.
RAV1 family members function as transcriptional regulators and play a positive role in plant disease resistance
(John Wiley & Sons, 2023) Chandan, Ravindra Kumar; Kumar, Rahul; Swain, Durga Madhab; Ghosh, Srayan; Bhagat, Prakash Kumar; Patel, Sunita; Bagler, Ganesh; Sinha, Alok Krishna; Jha, Gopaljee
Phytopathogens pose a severe threat to agriculture and strengthening plant defense response is an important strategy for disease control. Here, we report that AtRAV1, an AP2 and B3 domain-containing transcription factor is required for basal plant defense in Arabidopsis thaliana. The atrav1 mutant lines demonstrate hyper-susceptibility against fungal pathogens (Rhizoctonia solani and Botrytis cinerea) while AtRAV1 overexpressing (OE) lines exhibit disease resistance against them. Enhanced expression of various defense genes and activation of MAP kinases (AtMPK3 and AtMPK6) are observed in the R. solani infected OE lines, but not in the atrav1 mutant plants. In-vitro phosphorylation assay suggests AtRAV1 to be a novel phosphorylation target of AtMPK3. The bimolecular fluorescence complementation and yeast two-hybrid assay support physical interactions between AtRAV1 and AtMPK3. Overexpression of the native as well as phospho-mimic but not the phospho-defective variant of AtRAV1 impart disease resistance in the atrav1 mutant A. thaliana lines. On the other hand, overexpression of AtRAV1 fails to impart disease resistance in the atmpk3 mutant. These analyses emphasize that AtMPK3-mediated phosphorylation of AtRAV1 is important for the elaboration of defense response in A. thaliana. Considering that RAV1 homologs are conserved in diverse plant species, we propose that they can be gainfully deployed to impart disease resistance in agriculturally important crop plants. Indeed, overexpression of SlRAV1 (a member of the RAV1 family) imparts disease tolerance against not only fungal (R. solani and B. cinerea) but also against bacterial (Ralstonia solanacearum) pathogens in tomato, while silencing of the gene enhances disease susceptibility.
RS_CRZ1, a C2H2 type transcription factor is required for pathogenesis of Rhizoctonia solani AG1-IA in tomato
(American Phytopathological Society, 2021) Ghosh, Srayan; Kant, Ravi; Pradhan, Amrita; Jha, Gopaljee
Rhizoctonia solani is a necrotrophic fungal pathogen which causes disease in diverse plant species. In recent years, the genomic and transcriptomic studies have identified several candidate pathogenicity determinants of R. solani; however, most of them remain to be validated. In this study, we report a viral vector-based host induced gene silencing (HIGS) as well as a dsRNA (double stranded RNA) based approach to effectively downregulate genes of R. solani AG1-IA (BRS1 strain) during pathogenesis in tomato. We tested a few of the in-planta upregulated R. solani genes and observed that silencing of one of them i.e. RS_CRZ1 (a C2H2 type Zn finger transcription factor) significantly compromises the pathogenesis of R. solani in tomato. The RS_CRZ1 silenced plants not only exhibited significant reduction in disease symptoms, but the depth of pathogen colonization was also compromised. Furthermore, we identified the R. solani genes that were co-regulated with RS_CRZ1 during pathogenicity process. The HIGS mediated silencing of a few of them (CL1756Contig1; subtilisin like protease and CL1817Contig2; 2OG- Fe(II) oxygenase) compromised the pathogenesis of R. solani in tomato. The ectopic expression of RS_CRZ1 complemented the crz1 mutant of yeast and restored tolerance against various metal ion stress. Overall, our study reveals the importance of RS_CRZ1 in managing the hostile environment encountered during host colonization. Also, it emphasizes the relevance of HIGS and dsRNA-based gene silencing approach towards functional characterization of pathogenicity determinants of R. solani.
Rs_MEP1 is required for the pathogenesis of Rhizoctonia solani AG1-IA in plants
(The American Phytopathological Society (APS), 2026) Pradhan, Amrita; Sahoo, Debashis; Bhati, Vikrant; Kumar, Rahul; Yadav, Rajni; Ghosh, Srayan; Pawar, Prashant Anupama-Mohan; Jha, Gopaljee
Rhizoctonia solani AGI-IA is a polyphagous necrotrophic fungal pathogen that causes sheath blight disease in rice. Efforts are being made to identify pathogenicity-associated genes in R. solani and modulate them to develop a disease control strategy. Here, we investigate the roles of some predicted pathogenicity-associated genes of R. solani that have previously been reported to be upregulated during infection in rice. The tobacco rattle virus-based host-induced gene silencing of the selected pathogenicity-associated genes revealed that silencing of Rs_MEP1, a zinc-containing Peptidase_M43 domain-metalloprotease, severely compromises R. solani infection in tomato. Moreover, double-stranded RNA-mediated silencing of Rs_MEP1 prevented R. solani infection in rice. The signal sequence trap assay indicated the secretory nature of Rs_MEP1, while the reporter assay suggested its localization in the plant apoplast. Notably, agrobacterium-mediated transient overexpression of Rs_MEP1 induces necrotic cell death responses in plants. We provide evidence that Rs_MEP1 interacts with GH19 family of rice chitinases and potentially modulates their functions. Overall, our study emphasizes that Rs_MEP1 facilitates R. solani in promoting necrotic responses and targets rice GH19 chitinases to impart disease susceptibility in plants.