The Genome-Wide Mutation Shows the Importance of Cell Wall Integrity in Growth of the Psychrophilic Yeast Metschnikowia australis W7-5 at Different Temperatures.

In this study, it was found that a Cre/loxP system could be successfully used as a tool for editing the genome of the psychrophilic yeast Metschnikowia australis W7-5 isolated from Antarctica. The deletion and over-expression of the TPS1 gene for trehalose biosynthesis, the GSY gene for glycogen biosynthesis, and the GPD1 and GPP genes for glycerol biosynthesis had no influence on cell growth of the mutants and transformants compared to cell growth of their wild-type strain M. australis W7-5, indicating that trehalose, glycogen, and glycerol had no function in growth of the psychrophilic yeast at different temperatures. However, removal of the SLT2 gene encoding the mitogen-activated protein kinase in the cell wall integrity (CWI) signaling pathway and the SWI4 and SWI6 genes encoding the transcriptional activators Swi4/6 had the crucial influence on cell growth of the psychrophilic yeast at the low temperature, especially at 25 °C and expression of the genes related to cell wall and lipid biosynthesis. Therefore, the cell wall could play an important role in growth of the psychrophilic yeast at different temperatures and biosynthesis of cell wall was actively regulated by the CWI signaling pathway. This was the first time to show that the genome of the psychrophilic yeast was successfully edited and the molecular evidences were obtained to elucidate mechanisms of low temperature growth of the psychrophilic yeast from Antarctica.