摘要Cyclic nucleotide-gated ion channels(CNGCs)are key components in pattern-triggered immunity(PTI)signaling.Tight control of CNGC homeostasis is crucial for maintaining a balance between plant growth and immunity.Nevertheless,the mechanisms for fine-tuning CNGC homeostasis remain largely unknown.Here,we report that Arabidopsis thaliana CNGC3 is a functional calcium channel to mediate pattern-induced Ca2+influx,PTI,and resistance to Sclerotinia sclerotiorum.We identified a CNGC interactor,Skp1-interacting protein 31(SKIP31).In the absence of a pathogen,SKIP31 ubiquitinates CNGC3 at Lys8 and Lys33 of the K-X-V-R motif for degradation to repress plant immunity.When a pathogen attacks,activated receptor-like cytoplasmic kinase(RLCK)BOTRYTIS-INDUCED KINASE1(BIK1)phosphorylates SKIP31 to inhibit its ubiquitin ligase activity and interaction with the CNGC3 N-terminal region,thereby suppressing CNGC3 protein degradation to promote immunity.Phosphorylation within the F box of SKIP31 at Ser88 and Ser93 and at the C-terminal Ser261 prevents its interaction with Skp1 and CNGC3,respectively.These phos-phorylation sites are conserved in SKIP31 of different plant species,and SKIP31 interacts with all examined CNGCs,suggesting a pivotal role of SKIP31 phosphorylation in regulating CNGC stability and plant immunity.Moreover,biochemical assays revealed that BIK1 directly phosphorylates the CNGC3 cytoplasmic C-terminal region at four Ser residues to enhance its Ca2+channel activity,demonstrating dual roles of BIK1 in both pro-moting CNGC channel activity and stabilizing the channel protein.Collectively,our work unveils an SCF ubiq-uitin ligase-RLCK control system that fine-tunes the homeostasis of CNGCs for orchestrating plant immunity.