CALCIUM-DEPENDENT PROTEIN KINASE32 regulates cellulose biosynthesis through post-translational modification of cellulose synthase

Cellulose is an economically important source of food, paper, textiles, and biofuel. As an essential component of plant cell walls, cellulose is critical for plant cell growth. Despite its economic and biological significance, the regulation of cellulose biosynthesis is poorly understood. Phosphorylation and dephosphorylation of cellulose synthases (CESAs) were shown to impact the direction and velocity of cellulose synthase complexes (CSCs). Despite a high prevalence of phosphorylation sites in CESAs, the protein kinases that phosphorylate CESAs are largely unknown. Here, we demonstrate that CALCIUM-DEPENDENT PROTEIN KINASE32 (CPK32) regulates cellulose biosynthesis via phosphorylation of CESA3. Phosphorylation of CESA3 is important for the motility and stability of CSCs. Hence, we uncovered a new function of CPKs that regulates cellulose biosynthesis and a novel mechanism by which phosphorylation regulates the stability of CSCs.