Involved in a TGF-beta pathway (PubMed:8413626). May be a receptor for TGF-beta-like ligand daf-7 (PubMed:8413626). Controls the decision of whether or not larvae enter a developmentally arrested state, known as dauer, in response to environmental conditions (PubMed:8413626). Regulates body size and male tail patterning (PubMed:10887089, PubMed:21408209). Involved in regulating entry into quiescence triggered by satiety (PubMed:18316030). Involved in sensitivity to CO2 levels (PubMed:18524955). ATP + L-threonyl-[receptor-protein] = ADP + H(+) + O-phospho-L-threonyl-[receptor-protein] ATP + L-seryl-[receptor-protein] = ADP + H(+) + O-phospho-L-seryl-[receptor-protein] May interact with daf-1 to regulate dauer larva development (PubMed:10887089). Interacts with sma-10 (PubMed:20502686). Pharynx, intestine, hypodermis and body wall muscles in L1 through to adult stages. Also expressed in head neurons, ventral cord and tail neurons. Subset of head neurons show coexpression with daf-1 when dauer/nondauer decision is made. RNAi-mediated knockdown disrupts tail tip morphogenesis resulting in retention of the pointed larval tail tip in adult males (also known as the Lep phenotype). Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. TGFB receptor subfamily.