Serine/threonine-protein kinase required for wild-type hyphal growth and transcriptional regulation of cell-wall-associated genes. Involved in the biofilm formation through phosphorylation of the master regulator of biofilm formation BCR1. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with MOB2 and BCR1. In yeast cells, localizes to the cell cortex of small- and medium-budded cells and to the bud neck in large-budded cells. During hyphal growth, is present at the tip of hyphae and in the region of the septum. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. COT1 subfamily.