Isolation of Trichoderma reesei genes highly expressed on glucose-containing media: characterization of the tef1 gene encoding translation elongation factor 1α

Genes that are highly expressed on glucose-containing media were isolated from the filamentous fungus, Trichoderma reesei. A cDNA bank was prepared from glucose-grown fungus, the bank was screened with the same cDNA as a probe, and clones giving the strongest signal were isolated. This resulted in the isolation of previously uncharacterized genes. Five of the genes, representing the most abundant transcripts, corresponded to 1-3% of the total mRNA population and were clearly more highly expressed than the phosphoglycerate kinase-encoding gene (pgk1 ) of T. reesei. Based on sequence homology, one of the genes was identified as tef1, encoding translation elongation factor 1α (TEF). The T. reesei TEF is most related to the Mucor racemosus TEF3, showing an overall amino acid similarity of 85%. Interestingly, an exon of only 2 bp seems to be present in T. reesei tef1, comprising the first 2 bp of the Gly¹⁵ codon.