Identification and expression profiles of amino acid biosynthesis genes from psychrophilic yeast, glaciozyma antarctica

Abstract

The mechanism of amino acid uptake and synthesis in the psychrophilic microorganism lives and proliferate in the extreme low-temperature environment is still not well understood. The aim of this study was to identify genes involved in amino acid generation for psychrophilic yeast, Glaciozyma antarctica and to determine their expression profiles when cells grow in media rich in amino acids or with limited amount of amino acids. The identification of genes was carried out by generating expressed sequence tags (EST) from two cDNA libraries generated from cells grown in complex growth medium and minimal growth medium without amino acids. A total of 3552 cDNA clones from each library was randomly picked and sequenced, generating 1492 unique transcripts (complex medium) and 1928 unique transcripts (minimal medium). Homology analyses have identified genes encoding proteins required for free amino acid uptake, biosynthesis of amino acids and recycling of amino acids based on the pathway used in the model yeast, Saccharomyces cerevisiae. Gene expression analysis by RT-qPCR showed that genes required for free amino acid uptake showed a higher expression profile in the complex medium, whereas the expression of most genes encode for proteins essential for biosynthesis and recycling of amino acids are higher in the minimal medium. In summary, genes that are involved in the generation and the uptake of amino acids for psychrophilic microorganism are conserved as in their mesophilic counterparts and the expression of these genes are regulated in the presence or absent of free amino acids in the surrounding.