LysM receptor‐like kinase MdLYK3 destabilizes the ABA receptors PYR / PYLs to suppress ABA signaling in apple

ABA signaling is a central regulator of plant responses to abiotic stress. Similarly, LysM receptor-like kinases (LYKs) are well-established for their role in biotic stress responses. However, a potential function for LYKs in abiotic stress adaptation and their crosstalk with the ABA pathway remains largely unexplored. Here, we demonstrate that the apple LysM receptor-like kinase MdLYK3 negatively regulates drought resistance by targeting ABA receptors. MdLYK3 directly interacts with 11 of 13 ABA receptors and phosphorylates MdPYR1 (T113, S131) and MdPYL4 (S112, S130). This phosphorylation promotes their ubiquitination and subsequent proteasomal degradation, thereby suppressing ABA signaling. Intriguingly, ABA itself attenuates the MdLYK3-ABA receptor interaction, thereby stabilizing the receptors to sustain ABA signaling during stress. This dual regulatory mechanism uncovers a previously unrecognized link between microbial perception pathways and ABA-mediated abiotic stress adaptation. Our findings reveal how plants co-opt immune signaling components for environmental stress resilience, expanding the functional repertoire of LYKs beyond biotic interactions.