Essential for trafficking from prevacuolar compartments to vacuoles. Involved in the trafficking of newly synthesized protein to vacuoles. Essential for plant growth (PubMed:24824487). Participates in the recruitment of the core retromer components to the endosomal membrane by interacting with VPS35A (PubMed:23362252). Regulated by guanine nucleotide exchange factors (GEFs) which promote the exchange of bound GDP for free GTP. Regulated by the MON1-CCZ1 complex which serves as a link between Rab5 and Rab7 protein families in PVCs and mediates PVC maturation. Interacts with VPS35A. Partial co-localization with VPS3 at cytoplasmic punctate structures, and with VPS39 at subdomains of the vacuolar membrane. Co-localizes with VPS18. Over-expression of a dominant negative form of RABG3F (Asn-22) inhibits degradation of storage proteins in the protein storage vacuole and results in seedling death. Belongs to the small GTPase superfamily. Rab family.