Catalyzes the final step in the biosynthesis of the membrane lipid glucosylceramide (GluCer), the transfer of glucose to ceramide (Probable). Glucosylceramides play important roles in growth, differentiation and pathogenicity. Contribution to fungal pathogenesis is host-dependent (PubMed:17908205). an N-acylsphing-4-enine + UDP-alpha-D-glucose = a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + H(+) + UDP Lipid metabolism; sphingolipid metabolism. The D1, D2, D3, (Q/R)XXRW motif is a critical part of the GCS active site, involved in catalysis and UDP-sugar binding. Results in complete loss of glucosylceramides (GluCers) in mutant cells. Shows a significant change in the conidial morphology and displays a dramatic polar growth defect, and its mycelia are resistant to cell wall degrading enzymes. Shows increased resistance to plant defensins MsDef1 and RsAFP2, but not MsDef4. Belongs to the glycosyltransferase 2 family.