An Investigation of TDA1 Deficiency in Saccharomyces cerevisiae During Diauxic Growth.

Tda1p is a protein kinase in Saccharomyces cerevisiae. Here we investigate the function of TDA1 during the diauxic shift using transcriptomics. We compared the gene expression in the deletion mutant tda1∆ and the reference strain (BY4741) during both the aerobic fermentation phase (log phase), and the respiratory phase (post-diauxic shift phase, PDS) in three separate independent experiments. We found: Differential gene expression analysis showed that compared to the reference strain, the tda1∆ mutant exhibited an upregulation of the glucose repressed hexose transporter HXT6 during the log phase, and upregulation of mitochondrial proteins and genes related to mitochondrial translation during the PDS phase. Gene set enrichment analysis showed an enrichment in mitochondrial translation in the PDS phase for the deletion mutant tda1∆, but not for the reference strain. Transcription factor analysis showed that the enrichment of Mig1p repressed genes was not statistically significant in TDA1 deletion mutants for neither log-phase nor PDS-phase. This conflicted with the previously suggested model that argued for an interaction between Tda1p and Mig1p. Instead, transcription factor analysis showed an enrichment of genes regulated by the HAP-complex, which regulates mitochondrial translation, during the PDS-phase in the tda1∆ mutant. The combined evidence from this study indicates that Tda1p does not participate in Mig1p-mediated glucose repression. Instead, we propose that it is involved in the regulation of mitochondrial translation by repressing the expression of HAP complex subunits.