Serine/threonine-protein kinase required for cytoplasm to vacuole transport (Cvt) and autophagy as a part of the autophagy-specific VPS34 PI3-kinase complex I (By similarity). Required for pollen development and germination, probably via the modulation of phosphatidylinositol 3-phosphate (PI3P) formation and vacuolar organization (PubMed:21833541, PubMed:22361507). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with VPS34. Mainly expressed in anthers, pollen grains and pollen tubes, and, to a lower extent, in other tissues and organs including seedlings, roots, stems, leaves, flowers, pitils and siliques. In anthers, barely detected in microsporocytes at stage 6, but accumulates strongly in tetrads at stage 7, microspores, mature pollen grains, and tapetum cells. Also detectable in the growing pollen tubes on the stigma. Autophosphorylated. Reduced male gametophyte transmission. Abnormal pollen grains with unusual large vacuoles. Reduced pollen germination rescued by phosphatidylinositol 3-phosphate (PI3P) treatment. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.