Arabidopsis actin-binding protein WLIM2A links PAMP-triggered immunity and cytoskeletal organization

MAPKs are a family of highly conserved serine/threonine protein kinases that link upstream receptors to their downstream targets which can be localized in the cytoplasm or the nucleus. Pathogens produce pathogen-associated molecular patterns (PAMPs) that trigger the activation of MAPK cascades in plants. Phosphoproteomic analysis of PAMP-induced Arabidopsis plants led to the identification of several putative MAPK targets, WLIM2A. Here, we investigated the role of WLIM2A in plant immunity via a reverse-genetics approach generating wlim2a knockout lines using CRISPR-Cas9, as well as complementation and phosphosite mutated WLIM2A expression lines in the wlim2a background. The wlim2a lines were compromised in their response to Pst DC3000 but showed enhanced resistance to fungal infection by Botrytis cinereae. Transcriptome analyses revealed that immune hormone signaling and biosynthesis genes of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) are differentially regulated in the wlim2a knockout lines. Pathogen assays with Pst DC3000 showed altered stomatal phenotypes in wlim2a mutants. Importantly, WLIM2A phosphomutants had opposing stomatal behaviour and resistance phenotypes in response to Pst DC3000 infection. Overall, these data show that phosphorylation of WLIM2A by MAPKs regulates Arabidopsis stomatal immunity. Keywords: Plant immunity, cytoskeleton, stomata, phytohormones, MAPKs