Role of the hga1-encoded extracellular beta-galactosidase of Hypocrea jecorina in lactose metabolism and cellulase induction

Bernhard Seiboth, Lukas Hartl, Noora Salovuori, Jari Vehmaanperä, Merja Penttilä, Christian Kubicek

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

Abstract

Lactose is the only economic carbon source for protein production under the control of cellulase promoters by the ascomycete H. jecorina (anamorph: Trichoderma reesei). However, the mechanism by which lactose triggers cellulase formation is not understood. We have investigated the role of beta-galactosidase in lactose metabolism and cellulase induction in H. jecorina. A genomic copy of the bga1 gene predicting a protein with a MW of 111 kDa (incl. a signal sequence) was cloned using degenerate primers. The Bga1 belongs to the Glycosyl hydrolases family 35. Transcriptional analysis of the bga1 expression shows that it is highly expressed on L-arabinose, D-galactose and lower on lactose. Deletion of the gene showed that it is not essential for growth on lactose but that knock-out strains grew slower and produced about half the biomass of the wt strain, whereas amplification of the bga1 gene under the pki1 promoter resulted in faster growth with a reduced lag phase. Bga1 is not necessary for lactose-dependent induction of cbh1 gene expression in H. jecorina but its overexpression impairs lactose-induction of cbh1 expression. Analysis of the deletion strain further showed that bga1 encodes the major extracellular beta-galactosidase which is also partially cell-wall bound. An additional cell wall-bound beta-galactosidase activity could be shown but no evidence for an intracellular beta-galactosidase was obtained.
Original languageEnglish
Title of host publication22nd Fungal Genetics Conference at Asilomar
Subtitle of host publicationAbstracts from the 2003 Fungal Genetics Conference at Asilomar
DOIs
Publication statusPublished - 2003
Event22nd Fungal Genetics Conference - Asilomar, United States
Duration: 18 Mar 200322 Mar 2003

Publication series

SeriesFungal Genetics Reports
NumberArticle 18
Volume50

Conference

Conference22nd Fungal Genetics Conference
CountryUnited States
CityAsilomar
Period18/03/0322/03/03

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