Analysis of expressed sequence tags from the anamorphic basidiomycetous yeast, Pseudozyma antarctica, which produces glycolipid biosurfactants, mannosylerythritol lipids

Abstract

Pseudozyma antarctica T-34 secretes a large amount of biosurfactants (BS), mannosylerythritol lipids (MEL), from different carbon sources such as hydrocarbons and vegetable oils. The detailed biosynthetic pathway of MEL remained unknown due to lack of genetic information on the anamorphic basidiomycetous yeasts, including the genus Pseudozyma. Here, in order to obtain genetic information on P. antarctica T-34, we constructed a cDNA library from yeast cells producing MEL from soybean oil and identified the genes expressed through the creation of an expressed sequence tags (EST) library. We generated 398 ESTs, assembled into 146 contiguous sequences. Based upon a BLAST search similarity cut-off of E<or=10(-5), 21.4% of all contigs were orphan, while 78.6% showed similarity to sequences in the protein database; 60.3% of all contiguous sequences shared significant identities to hypothetical protein of Ustilago maydis, which is a smut fungus and BS producer. Based on the gene expression study using real-time reverse transcriptase-PCR, the predicted genes, such as mannosyltranferase and acyltransferase, were demonstrated to be highly involved in MEL biosynthesis in soybean oil-grown cells.