The calcium-permeable channel OSCA1.3 regulates plant stomatal immunity

Perception of biotic and abiotic stresses often leads to stomatal closure in plants. Rapid influx of calcium ions (Ca2+) across the plasma membrane plays an important role in this response, but the identity of Ca2+ channels involved has remained elusive. Here, we report that the Arabidopsis thaliana Ca2+-permeable channel OSCA1.3 controls stomatal closure during immunity. OSCA1.3 is rapidly phosphorylated upon perception of pathogen-associated molecular patterns (PAMPs). Biochemical and quantitative phospho-proteomics analyses reveal that the immune receptor associated cytosolic kinase BIK1 interacts with and phosphorylates the N-terminal cytosolic loop of OSCA1.3 within minutes of treatment with the peptidic PAMP flg22 derived from bacterial flagellin.