Dual localization of JA receptor, CaCOI2, explains JA perception dynamics in chickpea

Abstract

Jasmonates (JAs) form a group of oxylipin-derived phytohormones involved in multiple biotic and abiotic stress responses and regulate plant development. JAs are perceived by the receptor proteins, COI (coronatine insensitive). These JA receptors encoding F-box protein, form SCFCOI ubiquitin ligase complex (Skp, Cullin, F-box) and activate JA signaling by facilitating degradation of the transcriptional repressor (JAZ; Jasmonate associated ZIM domain containing) proteins through 26S proteasomal pathway. However, JA signaling is poorly understood in chickpea, a vital legume plant. Here, we first identified two putative chickpea JA receptor named CaCOI1, CaCOI2 and demonstrated CaCOI2 as a functional JA receptor. Further subcellular localization studies revealed that CaCOI2 is localized to extra-nuclear region and move to the nucleus on JA perception to activate JA signaling. Using domain swapping (between CaCOI1 and CaCOI2) experiments, we have demonstrated that the LRR region of JA receptors, which interact with bioactive JA i.e., JA-Ile, also plays a critical role in regulating subcellular localization of CaCOI proteins. We report that an acidic amino acid in F-box region of COI proteins (AtCOI1T29) stabilizes COI-InsP8 (1,5-bisdiphosphoinositol-1D-myo-inositol (2,3,4,6) tetrakisphosphate) interaction. This interaction is found to be critical for COI-JAZ interaction and therefore, their functionality. Our study thus identified a functional JA receptor in chickpea and revealed novel aspects of JA signaling and perception, which might also have implications in other plants.