Required for vacuole biogenesis and vacuole enlargment in dividing and expanding cells. Involved in the docking or fusion of prevacuolar vesicles. Important for the function of both male and female gametophytes, but is not essential for the germination and development of pollen. Core component of at least two putative endosomal tethering complexes, the homotypic fusion and vacuole protein sorting (HOPS) complex and the class C core vacuole/endosome tethering (CORVET) complex. Their common core is composed of the class C Vps proteins VPS11, VCL1, VPS18 and VPS33, which in HOPS further associates with VPS39 and VPS41 and in CORVET with VPS3. Expressed in roots, leaves, stems, siliques, flowers and mature pollen. Expressed throughout development. Absence of vacuoles in the embryo and accumulation of small vesicles and autophagosomes. Embryo lethality at late torpedo stage. Belongs to the VPS16 family.