Mannosyltransferase involved in glycosylphosphatidylinositol-anchor biosynthesis. Transfers the second mannose to the glycosylphosphatidylinositol during GPI precursor assembly. Required for the GPI-mediated endoplasmic reticulum exit and proper targeting to the cell surface of chp. Required for GPI-mediated membrane attachment of chp, qsm and Cont. Essential for microvillar stability in the rhabdomere (By similarity). Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Belongs to the PIGV family. Was originally named veg by similarity to the D.melanogaster ortholog. However, it was later shown that the veg phenotype does not map to this protein. It is still not known which gene corresponds to the veg phenotype.