title: Differential involvement of β-glucosidases from Hypocrea jecorina in rapid induction of cellulase genes by cellulose and cellobiose.
abstract: Appropriate perception of cellulose outside the cell by transforming it into an intracellular signal ensures the rapid production of cellulases by cellulolytic Hypocrea jecorina. The major extracellular β-glucosidase BglI (CEL3a) has been shown to contribute to the efficient induction of cellulase genes. Multiple β-glucosidases belonging to glycosyl hydrolase (GH) family 3 and 1, however, exist in H. jecorina. Here we demonstrated that CEL1b, like CEL1a, was an intracellular β-glucosidase displaying in vitro transglycosylation activity. We then found evidence that these two major intracellular β-glucosidases were involved in the rapid induction of cellulase genes by insoluble cellulose. Deletion of cel1a and cel1b significantly compromised the efficient gene expression of the major cellulase gene, cbh1. Simultaneous absence of BglI, CEL1a, and CEL1b caused the induction of the cellulase gene by cellulose to further deteriorate. The induction defect, however, was not observed with cellobiose. The absence of the three β-glucosidases, rather, facilitated the induced synthesis of cellulase on cellobiose. Furthermore, addition of cellobiose restored the productive induction on cellulose in the deletion strains. The results indicate that the three β-glucosidases may not participate in transforming cellobiose beyond hydrolysis to provoke cellulase formation in H. jecorina. They may otherwise contribute to the accumulation of cellobiose from cellulose as inducing signals.
authors.affiliation: State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, Shandong, People's Republic of China.
authors.forename: Qingxin
authors.initials: Q
authors.lastname: Zhou
authors.forename: Jintao
authors.initials: J
authors.lastname: Xu
authors.forename: Yanbo
authors.initials: Y
authors.lastname: Kou
authors.forename: Xinxing
authors.initials: X
authors.lastname: Lv
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Guolei
authors.initials: G
authors.lastname: Zhao
authors.forename: Weixin
authors.initials: W
authors.lastname: Zhang
authors.forename: Guanjun
authors.initials: G
authors.lastname: Chen
authors.forename: Weifeng
authors.initials: W
authors.lastname: Liu
mesh_terms: D002475:Cellobiose / Q000378:metabolism*; D002480:Cellulase / Q000235:genetics / Q000378:metabolism*; D044602:Cellulases / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D004790:Enzyme Induction; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006031:Glycosylation; D035901:Hypocrea / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D014170:Transformation, Genetic
chemical_list: D005656:Fungal Proteins; D011994:Recombinant Proteins; D002475:Cellobiose; D002482:Cellulose; D044602:Cellulases; D002480:Cellulase