Pepper G-type Lectin Receptor-like Kinase, CaRLK1, Modulates ABA-Mediated Stomatal Closure and Drought Tolerance

Lectin receptor-like kinases (LecRLKs) are plant-specific kinases that play critical roles in stress signaling. G-type LecRLKs, which possess an α-mannose-binding bulb lectin domain, are implicated in diverse stress responses; however, their roles in drought responses in pepper plants remain poorly understood. Therefore, this study aims to identify and functionally characterize a pepper G-type LecRLK, CaRLK1. CaRLK1 expression was significantly induced by multiple abiotic stresses, particularly dehydration. Additionally, functional analysis using virus-induced gene silencing revealed that CaRLK1-silenced pepper plants showed reduced drought tolerance and increased leaf water loss, associated with impaired stomatal closure and attenuated leaf temperature increases following abscisic acid (ABA) treatment. Moreover, CaRLK1 silencing reduced the expression of several drought-responsive genes, including CaOSR1, CaDREBLP1, and CaLOX1, under dehydration conditions. Collectively, these findings suggest that CaRLK1 functions as a positive regulator of drought stress responses in pepper plants by modulating ABA-dependent stomatal aperture dynamics and drought-responsive gene expression.