The putative transcription factor C a R tg3 is involved in tolerance to cations and antifungal drugs as well as serum‐induced filamentation in C andida albicans

The activated retrograde ( RTG ) pathway controls transcription of target genes through a heterodimer of transcription factors, R tg1 and R tg3, in S accharomyces cerevisiae . Here, we have identified the sole homologous gene C a RTG 3 that encodes a protein of 520 amino acids with characteristics of the basic helix–loop–helix/leucine zipper (b HLH / Z ip) family in C andida albicans . Deletion of C a RTG 3 results in C . albicans cells being sensitive to high concentrations of calcium and lithium cations as well as sodium dodecyl sulfate and activates the calcium/calcineurin signaling pathway in C . albicans cells. C a RTG 3 is also involved in the tolerance of C . albicans cells to the antifungal drugs azoles and terbinafine, but not to the antifungal drugs casponfungin and amphotericin B as well as the cell‐wall‐damaging reagents C alcoflour W hite and C ongo red. In contrast to S c R tg3, C a R tg3 is not involved in the osmolar response and is constitutively localized in the nucleus. However, deletion of C a RTG 3 results in a delay in serum‐induced filamentation of C . albicans cells. Therefore, C a R tg3 plays a role in tolerance to cations and antifungal drugs as well as serum‐induced filamentation in C . albicans .