The PP2A regulatory subunits, Cdc55 and Rts1, play distinct roles in Candida albicans’ growth, morphogenesis, and virulence

•cdc55 null mutant grows slowly as pseudohyphae with some cells lacking the nucleus.•rts1 null mutant cells are round and enlarged and seem to undergo incomplete cell separation producing multinucleated cells.•Strong chitin deposition occurs at the septum of cdc55 null mutant cells and on the surface of rts1 null mutant cells.•Deletion of cdc55 exhibits severe defects in hyphal and biofilm formation, while deletion of rts1 is partially defective.•cdc55 and rts1 null mutants show reduced virulence in mice. Protein phosphatase-2A (PP2A) is a heterotrimeric enzyme composed of a catalytic subunit, a regulatory subunit, and a structural subunit. In Candida albicans, Cdc55 and Rts1 have been identified as possible regulatory subunits of PP2A containing the catalytic subunit Pph21 and structural subunit Tpd3. The Tpd3-Pph21 phosphatase regulates cell morphogenesis and division. However, the functions of Cdc55 and Rts1 remain unclear. Here, we constructed cdc55Δ/Δ and rts1Δ/Δ mutants and found that they exhibit different defects in multiple phenotypes although both show similar hyperphosphorylation of the septin Sep7 and aberrant septin organization. Under yeast growth conditions, the cdc55Δ/Δ mutant grows slowly as pseudohyphae with some cells lacking the nucleus, while rts1Δ/Δ cells are round and enlarged and seem to undergo incomplete cell separation producing multinucleated cells. Strong chitin deposition occurs at the septum of cdc55Δ/Δ cells and on the surface of rts1Δ/Δ cells, which likely contributes to increased susceptibility to caspofungin. Also, cdc55Δ/Δ exhibits severe defects in hyphal and biofilm formation, while rts1Δ/Δ is partially defective. Both mutants show reduced virulence in mice, suggesting that PP2A-B subunits could serve as potential antifungal targets.