Pyruvate decarboxylase and thiamine biosynthetic genes are regulated differently by Pdc2 in S. cerevisiae and C. glabrata

Abstract

Understanding metabolism in the pathogenCandida glabratais key to identifying new targets for antifungals. The thiamine biosynthetic (THI) pathway is partially defective inC.glabrata, but the transcription factorCgPdc2 upregulates some thiamine biosynthetic and transport genes. One of these genes encodes a recently evolved thiamine pyrophosphatase (CgPMU3) that is critical for accessing external thiamine. Here, we demonstrate thatCgPdc2 primarily regulates THI genes. InSaccharomyces cerevisiae, Pdc2 regulates both THI and pyruvate decarboxylase (PDC) genes, with PDC proteins being a major thiamine sink. Deletion ofPDC2is lethal inS.cerevisiaein standard growth conditions, but not inC.glabrata. We uncover crypticciselements inC.glabrataPDC promoters that still allow for regulation byScPdc2, even when that regulation is not apparent inC.glabrata.C.glabratalacks Thi2, and it is likely that inclusion of Thi2 into transcriptional regulation inS.cerevisiaeallows for a more complex regulation pattern and regulation of THI and PDC genes. We present evidence that Pdc2 functions independent of Thi2 and Thi3 in both species. The C-terminal activation domain of Pdc2 is intrinsically disordered and critical for species differences. Truncation of the disordered domains leads to a gradual loss of activity. Through a series of cross species complementation assays of transcription, we suggest that there are multiple Pdc2-containing complexes, andC.glabrataappears to have the simplest requirement set for THI genes, except forCgPMU3.CgPMU3has differentcisrequirements, but still requires Pdc2 and Thi3 to be upregulated by thiamine starvation. We identify the minimal region sufficient for thiamine regulation inCgTHI20,CgPMU3, andScPDC5promoters. Defining thecisandtransrequirements for THI promoters should lead to an understanding of how to interrupt their upregulation and provide targets in metabolism for antifungals.