The changes in Tps1 activity, trehalose content and expression of TPS1 gene in the psychrotolerant yeast Guehomyces pullulans 17-1 grown at different temperatures.

The psychrotolerant yeast Guehomyces pullulans 17-1 grows the best at 15 °C. When the yeast cells grown at 15 °C for 48 h were transferred to new medium and grown at 10, 15, and 25 °C, respectively, trehalose-6-phosphate synthase (Tps1) activity and trehalose content of the yeast cells grown at 25 °C were higher than those of the yeast cells grown at 10 and 15 °C. However, Tps1 activity and trehalose content of the yeast cells grown at 10 °C were lower than those of the yeast cells grown at 15 °C. This may suggest that trehalose synthesized by G. pullulans 17-1 only can play more important role in its adaption to high temperature than in its adaption to low temperature. After the GPTPS1 gene encoding trehalose-6-phosphate synthase was cloned from the psychrotolerant yeast, it was found that the promoter of the gene contained several stress-response elements such as C4T and AG4, indicating that the gene expression might be regulated by heat shock. It was also found that the transcriptional level of the GPTPS1 gene in the yeast cells grown at 25 °C was higher than that of the GPTPS1 gene in the yeast cells grown at 10 and 15 °C. However, the transcriptional level of the GPTPS1 gene in the yeast cells grown at 10 °C was lower than that of the yeast cells grown at 15 °C. This meant that expression of the GPTPS1 gene was constant with the changes in Tps1 activity and trehalose content of the yeast cells.