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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.
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    The Ca2+ channel CNGC19 regulates Arabidopsis defense against spodoptera herbivory
    (American Society of Plant Biologists, 2019) Meena, Mukesh Kumar; Prajapati, Ramgopal; Krishna, Deepthi; Divakaran, Keerthi; Pandey, Yogesh; Reichelt, Michael; Mathew, M.K.; Boland, Wilhelm; Mithöfer, Axel; Vadassery, Jyothilakshmi
    Cellular calcium elevation is an important signal used by plants for recognition and signaling of environmental stress. Perception of the generalist insect, Spodoptera litura, by Arabidopsis thaliana activates cytosolic Ca2+ elevation, which triggers downstream defense. However, not all the Ca2+ channels generating the signal have been identified, nor are their modes of action known. We report on a rapidly activated, leaf vasculature- and plasma membrane-localized, CYCLIC NUCLEOTIDE GATED CHANNEL19 (CNGC19), which activates herbivory-induced Ca2+ flux and plant defense. Loss of CNGC19 function results in decreased herbivory defense. The cngc19 mutant shows aberrant and attenuated intra-vascular Ca2+ fluxes. CNGC19 is a Ca2+ permeable channel, as hyperpolarization of CNGC19-expressing Xenopus oocytes in the presence of both cAMP and Ca2+ results in Ca2+ influx. Breakdown of Ca2+-based defence in cngc19 mutants leads to a decrease in herbivory-induced JA-Ile biosynthesis and expression of JA responsive genes. cngc19 mutants are deficient in aliphatic glucosinolate accumulation and hyperaccumulate its precursor, methionine. CNGC19 modulates aliphatic glucosinolate biosynthesis in tandem with BRANCHED-CHAIN AMINO ACID TRANSAMINASE4 (BCAT4), which is involved in the chain elongation pathway of Met-derived glucosinolates. Furthermore, CNGC19 interacts with herbivory-induced CALMODULIN2 (CaM2) in planta. Together, our work reveals a key mechanistic role for the Ca2+ channel CNGC19 in the recognition of herbivory and the activation of defense signaling.