Fig. 2: Induction of AOX2 supports alternative carbon source utilization upon genetic or chemical compromise of classical respiration.

a Aox activity is essential for C. albicans cytochrome pathway mutants to utilize galactose. Indicated genes were deleted in a wild-type (WT) or a homozygous aox1/aox2-deletion (aox) parent. Growth was monitored by spotting on YPD and YPGal agar. The respiratory complex impaired by each deletion is in parentheses. b Respiratory complex deletion mutants grown in galactose-containing medium overexpress AOX2. Expression in the wild-type (WT) was used to calculate relative AOX2 levels across samples cultured in the same medium. c WT and mutant strains were grown in synthetic complete (SC) medium containing galactose or glycerol and two-fold serial dilutions of antimycin A (AA) or Inz-5. For each strain, growth (OD₆₀₀) in drug-free medium was used to normalize growth in the presence of an inhibitor (see color bar). All dose-response assays are presented in the same format hereafter, unless otherwise specified. d Time-course of AOX induction upon AA treatment. C. albicans was treated with AA (10 μM) in YPGal or YPGly medium. AOX1 and AOX2 transcript levels were measured at each time point. Basal expression for each gene (time 0) was set to 1 for each condition. e Lysates were prepared from an untagged strain and strains expressing proteins tagged at the C-terminus with 6XHis-3XFlag (Aox1-HF or Aox2-HF) after 12-hours growth in YPGly+AA (10 μM), resolved by SDS-PAGE, and blots probed with anti-Flag antibody. Coomassie blue staining (CBS) of a replicate gel was used to confirm equal loading. The amount of Aox2-HF lysate was titered. Asterisk: the non-specific band. f Aox2-RFP fusion localizes to mitochondria. Images were acquired by fluorescence microscopy of cells that express Aox2-RFP (magenta) and Tom70-GFP (mitochondrial marker, green) following growth in YPGly containing AA (10 μM) or DMSO (0.1%). Scale bar, 10 μm. g AOX1 functionally complements AOX2 when driven by the inducible AOX2 promoter. Relative growth inhibition by AA in SC-galactose medium is presented as in c. b, d present mean (SD) of technical triplicates from an experiment representative of biological duplicates with comparable results.