Transcriptomic response of an Antarctic yeast Rhodotorula sp. USM-PSY62 to temperature changes

Rhodotorula sp. (USM-PSY62) is a psychrophilic yeast isolated from Antarctic sea ice and it grows optimally at 15 °C. This study was set up to observe how USM-PSY62 adapted to fluctuations in temperature. During cold adaptation, an elevated transcription of the CorA magnesium transporter gene in USM-PSY62 indicated a higher requirement for magnesium ions in order to gain additional enzyme cofactors or maintain cytoplasmic fluidity. The HepA homologue coding for DNA/RNA helicase was also over-expressed in cold condition possibly to reorganize secondary structures of DNA and RNA. An up-regulation of the catalase gene was also observed reflecting an increment in the concentration of reactive oxygen species and fluctuations in the associated antioxidant system. The YOP1 gene, which encodes a membrane protein associated with protein transport and membrane traffic, was the most down-regulated under cold shock condition. The genes responsible for the structural maintenance of chromosome (SMC) were also down-regulated when the temperature was shifted to 0 °C. Upon cold shock, the gene for heat shock factor protein 1 (HSF1) was also down-regulated. Hsf1 is a transcriptional regulator which regulate the heat shock responses. Although USM-PSY62 showed some common adaptive strategies as in several other psychrophilic organisms, new mechanisms were also uncovered.