Abstract text: Plant cell walls not only serve as structural barriers that protect cells but also function as dynamic signaling platforms that perceive extracellular cues to coordinate plant growth, development, and stress responses. This surveillance system is largely mediated by cell wall–associated signaling networks involving diverse protein kinases. However, despite an increasing repertoire of cell surface receptors, the mechanisms underlying phosphorylation-mediated signal transduction remain poorly understood. In this study, we exposed a library of phosphatase mutants to cell wall damage and found that mutations in KAPP led to increased sensitivity to the cellulose synthase inhibitor C17. Surprisingly, through functional fluorescently-tagged KAPP lines, we found that it localized to the tonoplast contrary to former dogma. Through proximity labelling approaches^{1, 2}, we further found that KAPP interacts with the cytosolic kinase SIK1 (a MAP4K), which we confirmed via in vitro assays. Genetic interactions show how KAPP and SIK1 work in a phospho-relay loop responses to cell wall stress. Given SIK1 being a MAP4K and its function in plant growth and immunity, we outline a new cell wall signaling module acting immediately downstream of cell surface receptors. 

References

1. Adv. Sci.2025, 12, 2414496. 

2. Nat Commun 16, 872 (2025).