Institutional Publications

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    Secret weapon of insects: The oral secretion cocktail and its modulation of host immunity
    (Oxford University Press, 2024) Prajapati, Vinod Kumar; Vijayan, Vishakh; Vadassery, Jyothilakshmi
    Plants and insects have co-existed for almost 400 million years and their interactions can be beneficial or harmful, thus reflecting their intricate co-evolutionary dynamics. Many herbivorous arthropods cause tremendous crop loss, impacting the agro-economy worldwide. Plants possess an arsenal of chemical defenses that comprise diverse secondary metabolites that help protect against harmful herbivorous arthropods. In response, the strategies that herbivores use to cope with plant defenses can be behavioral, or molecular and/or biochemical of which salivary secretions are a key determinant. Insect salivary secretions/oral secretions (OSs) play a crucial role in plant immunity as they contain several biologically active elicitors and effector proteins that modulate plants’ defense responses. Using this oral secretion cocktail, insects overcome plant natural defenses to allow successful feeding. However, a lack of knowledge of the nature of the signals present in oral secretion cocktails has resulted in reduced mechanistic knowledge of their cellular perception. In this review, we discuss the latest knowledge on herbivore oral secretion derived elicitors and effectors and various mechanisms involved in plant defense modulation. Identification of novel herbivore-released molecules and their plant targets should pave the way for understanding the intricate strategies employed by both herbivorous arthropods and plants in their interactions.
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    Ubiquitination from the perspective of plant pathogens
    (Oxford University Press, 2023) Sharma, Shambhavi; Prasad, Ashish; Prasad, Manoj
    The constant battle of survival between pathogens and host plants has played a crucial role in shaping the course of their co-evolution. However, the major determinants of the outcome of this ongoing arms race are the effectors secreted by pathogens into the host cells. These effectors perturb the defense responses of plants to promote their successful infection. In recent years, the extensive research in the area of effector biology has reported an increase in the repertoire of pathogenic effectors that mimics or targets the conserved ubiquitin proteasomal pathway. The role of ubiquitin mediated degradation pathway has been well known to be indispensable for various aspects of plant’s life, thus targeting or mimicking it seems to be a smart strategy adopted by pathogens in their favor. Therefore, this review summarizes the recent findings on how some pathogenic effectors mimics or act as one of the components of ubiquitin proteasomal machinery while others directly target the plant’s ubiquitin proteasomal system.
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    Calcium regulates the mycophagous ability of Burkholderia gladioli strain NGJ1 in a type III secretion system-dependent manner
    (BioMed Central Ltd, 2020) Yadav, Sunil Kumar; Das, Joyati; Kumar, Rahul; Jha, Gopaljee
    Background: A rice associated bacterium Burkholderia gladioli strain NGJ1 demonstrates mycophagy, a phenomenon wherein bacteria feed on fungi. Previously, we have reported that NGJ1 utilizes type III secretion system (T3SS) to deliver a prophage tail-like protein (Bg_9562) into fungal cells to establish mycophagy. Results: In this study, we report that calcium ion concentration influences the mycophagous ability of NGJ1 on Rhizoctonia solani, an important fungal pathogen. The calcium limiting condition promotes mycophagy while high calcium environment prevents it. The expression of various T3SS apparatus encoding genes of NGJ1 was induced and secretion of several potential T3SS effector proteins (including Bg_9562) into extracellular milieu was triggered under calcium limiting condition. Using LC-MS/MS proteome analysis, we identified several calcium regulated T3SS effector proteins of NGJ1. The expression of genes encoding some of these effector proteins was upregulated during mycophagous interaction of NGJ1 with R. solani. Further, mutation of one of these genes (endo-β-1, 3- glucanase) rendered the mutant NGJ1 bacterium defective in mycophagy while complementation with full length copy of the gene restored its mycophagous activity. Conclusion: Our study provides evidence that low calcium environment triggers secretion of various T3SS effectors proteins into the extracellular milieu and suggests the importance of cocktail of these proteins in promoting mycophagy
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    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.
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    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.