Differential expression of genes from Penicillium purpurogenum when grown on sugar beet pulp and glucose as carbon sources

Penicillium purpurogenum is a filamentous ascomycete which grows on a variety of natural carbon sources, among them sugar beet pulp, and secretes a large variety of cellulolytic and hemicellulolytic enzymes into the culture medium. The purpose of this work was to analyse the difference in the expression of genes when those transcribed in a medium with glucose as carbon source (a highly repressive substrate) are subtracted from those expressed when it is grown on sugar beet pulp. A subtractive cDNA library was constructed by means of suppression subtractive hybridization. In all, 101 clones were selected and 80 were found to have inserts of cDNA differentially expressed in sugar beet pulp. These cDNAs were sequenced and were queried for similarities with BLAST. Sixty-two unique expressed sequence tags (ESTs) of interest were obtained. Of them, 58% are unidentified and 5% are unclassified. The remaining sequences correspond to: 18% metabolism, 5% gene/protein expression, 5% cell/organism defence, 6% cell signalling/cell communication and 3% cell division. The complete sequences of the genes and cDNAs of two of the ESTs was performed; one of them (EST 19) codes for a putative transcriptional regulator and the other (EST 182) for a putative DNA repair protein.