Protein mannosyltransferase (PMT) involved in hyphal growth and drug sensitivity. Transfers mannose from Dol-P-mannose to Ser or Thr residues on proteins. PMT1, PMT2 and PMT4 account for most of the protein-O-glycosylation activity, while PMT5 and PMT6 may specifically modulate a much narrower spectrum of target proteins. Accounts for the O-glycosylation of the cell wall proteins KRE9, PIR2, RHD3, and ALS1, as well as the SEC20 t-SNARE component. O-glycosylation of SEC20 is essential for its stability. Required for filamentation and early phases of biofilm formation. a dolichyl beta-D-mannosyl phosphate + L-seryl-[protein] = 3-O-(alpha-D-mannosyl)-L-seryl-[protein] + a dolichyl phosphate + H(+) a dolichyl beta-D-mannosyl phosphate + L-threonyl-[protein] = 3-O-(alpha-D-mannosyl)-L-threonyl-[protein] + a dolichyl phosphate + H(+) Protein modification; protein glycosylation. PMT1 and PMT2 form a functional heterodimer. Transcript levels are increased at least twofold by tunicamycin and Congo red. Both MSB2 and CEK1 are required to down-regulate PMT1 transcript levels in cells with intact glycostructures. Shows altered cell wall composition with a significant decrease in wall mannoproteins. Impairs biofilm formation and shows reduced virulence in a mouse model of hematogenously disseminated candidiasis (HDC) and using reconstituted human epithelium (RHE) or engineered human oral mucosa (EHOM). Belongs to the glycosyltransferase 39 family.