Browsing by Author "Varma, Mahendra"

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Calcium channel CNGC19 mediates basal defense signaling to regulate colonization of Piriformospora indica in Arabidopsis roots
(Oxford University Press, 2020) Jogawat, Abhimanyu; Meena, Mukesh Kumar; Kundu, Anish; Varma, Mahendra; Vadassery, Jyothilakshmi
The activation of calcium signaling is a crucial event for perceiving environmental stress. Colonization by Piriformospora indica, a growth promoting root endosymbiont activates cytosolic Ca2+ in Arabidopsis roots. In this study, we analyze the role of calcium channels responsible for Ca2+ fluxes and its functional relevance. Expression profiling revealed that CNGC19 is a early activated gene, induced by unidentified components in P. indica cell wall extract. Functional analysis revealed that loss-of-function of CNGC19 results in growth inhibition by P.indica, due to increased colonization and loss of controlled P. indica growth. P. indica cell wall extract induced cytosolic Ca2+ elevation is reduced in cngc19 mutant indicating a role in generation of Ca2+cyt elevation. MAMP-trigerred immunity (MTI) is compromised in cngc19 lines as evident from unaltered callose deposition, reduced cis-OPDA, JA and JA-Ile levels and downregulation of jasmonate and other defense related genes which contributes to shift towards pathogenic response. Loss-of-function of CNGC19 results in inability to modulate indole glucosinolate content during P. indica-colonization. CNGC19 mediated basal immunity is AtPep receptor, PEPR dependent. CNGC19 is also crucial for P. indica mediated suppression of AtPep induced immunity. Thus, Arabidopsis CNGC19 is an important Ca2+ channel, maintaining a robust innate immunity and crucial for growth promotion signalling upon P. indica colonization.
External jasmonic acid isoleucine mediates amplification of plant elicitor peptide receptor (PEPR) and jasmonate-based immune signalling
(John Wiley & Sons, 2024) Mittal, Deepika; Gautam, Janesh Kumar; Varma, Mahendra; Laie, Amrutha; Mishra, Shruti; Behera, Smrutisanjita; Vadassery, Jyothilakshmi
Jasmonic acid-isoleucine (JA-Ile) is a plant defence hormone whose cellular levels are elevated upon herbivory and regulate defence signalling. Despite their pivotal role, our understanding of the rapid cellular perception of bioactive JA-Ile is limited. This study identifies cell type-specific JA-Ile-induced Ca2+ signal and its role in self-amplification and plant elicitor peptide receptor (PEPR)-mediated signalling. Using the Ca2+ reporter, R-GECO1 in Arabidopsis, we have characterized a monophasic and sustained JA-Ile-dependent Ca2+ signature in leaf epidermal cells. The rapid Ca2+ signal is independent of positive feedback by the JA-Ile receptor, COI1 and the transporter, JAT1. Microarray analysis identified up-regulation of receptors, PEPR1 and PEPR2 upon JA-Ile treatment. The pepr1 pepr2 double mutant in R-GECO1 background exhibits impaired external JA-Ile induced Ca2+cyt elevation and impacts the canonical JA-Ile responsive genes. JA responsive transcription factor, MYC2 binds to the G-Box motif of PEPR1 and PEPR2 promoter and activates their expression upon JA-Ile treatment and in myc2 mutant, this is reduced. External JA-Ile amplifies AtPep-PEPR pathway by increasing the AtPep precursor, PROPEP expression. Our work shows a previously unknown non-canonical PEPR-JA-Ile-Ca2+-MYC2 signalling module through which plants sense JA-Ile rapidly to amplify both AtPep-PEPR and jasmonate signalling in undamaged cells.
In silico identification of effector proteins from generalist herbivore Spodoptera litura
(BioMed Central Ltd, 2020) Prajapati, Vinod Kumar; Varma, Mahendra; Vadassery, Jyothilakshmi
Background: The common cutworm, Spodoptera litura Fabricius is a leaf and fruit feeding generalist insect of the order Lepidoptera and a destructive agriculture pest. The broad host range of the herbivore is due to its ability to downregulate plant defense across different plants. The identity of Spodoptera litura released effectors that downregulate plant defense are largely unknown. The current study aims to identify genes encoding effector proteins from salivary glands of S. litura (Fab.). Results: Head and salivary glands of Spodoptera litura were used for de-novo transcriptome analysis and effector prediction. Eight hundred ninety-nine proteins from the head and 330 from salivary gland were identified as secretory proteins. Eight hundred eight proteins from the head and 267 from salivary gland proteins were predicted to be potential effector proteins. Conclusions: This study is the first report on identification of potential effectors from Spodoptera litura salivary glands.