Authors: Michael Günther Christian Grumaz Stefan Lorenz Philip Stevens Elena Lindemann Thomas Hirth Kai Sohn Susanne Zibek Steffen Rupp
Publish Date: 2015/01/15
Volume: 99, Issue: 3, Pages: 1375-1388
Abstract
The basidiomycetous fungus Pseudozyma aphidis is able to convert vegetable oils to abundant amounts of the biosurfactant mannosylerythritol lipid MEL with a unique product pattern of MELA MELB MELC and MELD To investigate the metabolism of MEL production we analyzed the transcriptome of P aphidis DSM 70725 under MELinducing and noninducing conditions using deep sequencing Following manual curation of the previously described in silico gene models based on RNASeq data we were able to generate an experimentally verified gene annotation containing 6347 genes Using this database our expression analysis revealed that only four of the five cluster genes required for MEL synthesis were clearly induced by the presence of soybean oil The acetyltransferase encoding gene PaGMAT1 was expressed on a much lower level which may explain the secretion of MEL with different degrees of acetylation in P aphidis In parallel to MEL synthesis microscopic observations showed morphological changes accompanied by expression of genes responsible for cell development indicative of a coregulation between MEL synthesis and cell morphology In addition a set of transcription factors was identified which may be responsible for regulation of MEL synthesis and cell development The upregulation of genes required for nitrogen metabolism and other assimilation processes indicate additional metabolic pathways required under the MELinducing conditions used We also searched for a conserved gene cluster for cellobiose lipids CL but only found seven genes with limited homology distributed over the genome However we detected characteristic TLC spots in fermentations using P aphidis DSM 70725 indicative of CL secretion
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