Characterization of the protein processing and secretion pathways in a comprehensive set of expressed sequence tags from Trichoderma reesei.

Trichoderma reesei is a filamentous fungus widely used as an efficient protein producer and known to secrete large quantities of biomass degrading enzymes. Much work has been done aimed at improving the secretion efficiency of this fungus. It is generally accepted that the major bottlenecks in secretion are protein folding and ornamentation steps in this pathway. In an attempt to identify genes involved in these steps, the 5' ends of 21888 cDNA clones were sequenced from which a unique set of over 5000 were also 3' sequenced. Using annotation tools Gene Ontology terms were assigned to 2732 of the sequences. Homologs to the majority of Aspergillus niger's Srg genes as well as a number of homologs to genes involved in protein folding and ornamentation pathways were identified.

Characterization of the promoter and upstream activating sequence from the Pseudomonas alcaligenes lipase gene.

Pseudomonas alcaligenes secretes a lipase with a high pH optimum, which has interesting properties for application in detergents. The expression of the lipase is strongly dependent on the presence of lipids in the growth medium such as soybean oil. The promoter of the gene was characterized and found to have resemblance to sigma54 controlled promoters, which are known to be tightly regulated. The transcription start was mapped precisely downstream of a sequence with close similarity to the -12/-24 consensus sequence of sigma54 controlled promoters. Interestingly, a hyperproducer mutant strain was isolated and found to have a C to T mutation in the -12/-24 promoter consensus region. In addition an Upstream Activating Sequence (UAS) with homology to sigma54 UAS consensus sequences was identified. It was demonstrated that an increase of the distance from the UAS to the transcription start or the deletion of the UAS results in significantly lower expression levels of lipase. A systematic mutational analysis of the UAS sequence has resulted in a variant with an increased lipase expression.