The Ca²⁺ Channel CNGC19 Regulates Arabidopsis Defense Against Spodoptera Herbivory

Abstract

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 (Arabidopsis thaliana) activates cytosolic Ca 21 elevation, which triggers downstream defense. However, not all the Ca 21 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 Ca 21 flux and plant defense. Loss of CNGC19 function results in decreased herbivory defense. The cngc19 mutant shows aberrant and attenuated intravascular Ca 21 fluxes. CNGC19 is a Ca 21-permeable channel, as hyperpolarization of CNGC19-expressing Xenopus oocytes in the presence of both cyclic adenosine monophosphate and Ca 21 results in Ca 21 influx. Breakdown of Ca 21-based defense in cngc19 mutants leads to a decrease in herbivory-induced jasmonoyl-l-isoleucine biosynthesis and expression of JA responsive genes. The 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, which is involved in the chain elongation pathway of Met-derived glucosinolates. Furthermore, CNGC19 interacts with herbivory-induced CALMODULIN2 in planta. Together, our work reveals a key mechanistic role for the Ca 21 channel CNGC19 in the recognition of herbivory and the activation of defense signaling.

Plant immune signaling: Advancing on two frontiers

“…The MAMP‐induced stomatal closure is abolished in mutants that loss of function of MPK3/6 or their upstream MKK4/5 independently of abscisic acid (ABA) signaling (Su et al 2017). Moreover, the SERK family RLKs positively regulate stomatal closure by transmitting immune signals from PRR complex to downstream MAPKKK protein YDA (Meng et al 2015). Importantly, recent studies demonstrated that PRR complex can also regulate stomatal closure through a short signals transduction module.…”

Surface Sensor Systems in Plant Immunity

“…Phosphorylation of AtCNGC2/4 by AtBIK1 is critical for calcium spiking in response to immune elicitors (Tian et al, 2019). The related channel proteins AtCNGC19 and 20 have recently been implicated in regulation of AtBAK1-dependent cell death containment in plant immunity (Yu et al, 2019), and AtCNGC19 has further been shown to have a role in resistance against insect herbivory (Meena et al, 2019). It is not yet known if BIK1 also has a role in activating AtCNGC19 and AtCNGC20.…”

Plant Cyclic Nucleotide-Gated Channels: New Insights on Their Functions and Regulation

“…Like CNGC2 and CNGC4, the two closely related group-I channels CNGC11 and CNGC12 have been implicated in immunity and PCD (Yoshioka et al, 2006;Moeder et al, 2011). Likewise, a role in immunity, wound signaling, and insect resistance has been proposed for CNGC19 and CNGC20, which comprise subclade IVa in the CNGC family (Moeder et al, 2011;Meena et al, 2019). BAK1 and SERK4 are involved in a wide variety of physiological phenomena and the bak1-4 serk4-1 double mutant develops severe postembryonic lethality due to hyperactivation of PCD (He et al, 2007;de Oliveira et al, 2016).…”