Functional analysis of glycoside hydrolase family 18 and 20 genes in Neurospora crassa

Fungal Genet Biol. 2012 Sep;49(9):717-30. doi: 10.1016/j.fgb.2012.06.013. Epub 2012 Jul 13.

Abstract

Glycoside hydrolase family 18 contains hydrolytic enzymes with chitinase or endo-N-acetyl-β-D-glucosaminidase (ENGase) activity, while glycoside hydrolase family 20 contains enzymes with β-N-acetylhexosaminidase (NAGase) activity. Chitinases and NAGases are involved in chitin degradation. Chitinases are phylogenetically divided into three main groups (A, B and C), each further divided into subgroups. In this study, we investigated the functional role of 10 Neurospora crassa genes that encode chitinases, 2 genes that encode ENGases and 1 gene that encode a NAGase, using gene deletion and gene expression techniques. No phenotypic effects were detected for any of the studied group A chitinase gene deletions. Deletion of the B group member chit-1 resulted in reduced growth rate compared with the wild type (WT) strain. In combination with the presence of a predicted glycosylphosphatidylinositol anchor motif in the C-terminal of chit-1, indicating cell wall localization, these data suggest a role in cell wall remodeling during hyphal growth for chit-1. Deletion of the ENGase gene gh18-10 resulted in reduced growth rate compared with WT, increased conidiation, and increased abiotic stress tolerance. In addition, Δgh18-10 strains displayed lower secretion of extracellular proteins compared to WT and reduced levels of extracellular protease activity. The connection between gh18-10 ENGase activity and the endoplasmic reticulum associated protein degradation process, a stringent quality control of glycoprotein maturation, is discussed. N. crassa group C chitinase genes gh18-6 and gh18-8 were both induced during fungal-fungal interactions. However, gh18-6 was only induced during interspecific interactions, while gh18-8 displayed the highest induction levels during self-self interactions. These results provide new information on functional differentiation of fungal chitinases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Wall / chemistry
  • Cell Wall / enzymology
  • Cell Wall / genetics
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Glycoside Hydrolases / chemistry
  • Glycoside Hydrolases / genetics
  • Glycoside Hydrolases / metabolism*
  • Multigene Family*
  • Neurospora crassa / chemistry
  • Neurospora crassa / enzymology*
  • Neurospora crassa / genetics
  • Protein Structure, Tertiary
  • Protein Transport

Substances

  • Fungal Proteins
  • Glycoside Hydrolases