Receptor kinase involved in the regulation of thermotolerance (PubMed:26280413). Functions as positive regulator of heat tolerance (PubMed:26280413). May be involved in the regulation of cell proliferation and cell growth (PubMed:29692796). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] No visible phenotype under normal growth conditions, but mutant plants cannot survive when grown under heat conditions (42 degres Celsius during the day and 35 degres Celsius during the night) (PubMed:26280413). Reduced plant height and reduced panicle length (PubMed:29692796). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.