Isolation and characterization of the Aspergillus nidulans eglC gene encoding a putative β-1,3-endoglucanase

Abstract

The Aspergillus nidulans eglC gene, which encodes a putative beta-1,3-endoglucanase, was isolated from a chromosome-specific library by using an expressed sequence tag, esd0113. The EglC open reading frame encodes a 465 amino acid polypeptide, of which the amino acid sequence showed 46% similarity to that of Saccharomyces cerevisiae beta-1,3-endoglucanase. The eg/C transcript level at the early stages of asexual and sexual developments was dependent on the presence of the nsdD gene that encodes a GATA-type transcription factor, confirming that the nsdD gene is necessary for full accumulation of the eg/C transcript. Deletion of the egIC gene did not affect the radial growth rate, the germination rate of conidia, and both of asexual and sexual development. However, deletion of the gene led to hyphae more resistant to a cell wall-lyzing enzyme, implying that the cell wall structure of the eg/C-null mutant is altered from a wild type one. Furthermore, deletion of the fadA and sfaD genes, that encode a G alpha and a G beta subunits of a heterotrimeric G protein, respectively, did not affect the eg/C transcript level at the early developmental stages. In contrast, deletion of the flb A gene, that codes for a regulatory protein having an RGS (regulator of G protein signaling) motif, led to decrease in the eg/C transcript level. The eg/C transcript level was not higher in a creA mutant than in a wild type, indicating that the eg/C gene is not sensitive to carbon-catabolite repression. (c) 2005 Elsevier Inc. All rights reserved.