Aberrant protein N-glycosylation impacts upon infection-related growth transitions of the haploid plant-pathogenic fungus Mycosphaerella graminicola

Mol Microbiol. 2011 Jul;81(2):415-33. doi: 10.1111/j.1365-2958.2011.07701.x. Epub 2011 May 31.

Abstract

The ascomycete fungus Mycosphaerella graminicola is the causal agent of Septoria Tritici Blotch disease of wheat and can grow as yeast-like cells or as hyphae depending on environmental conditions. Hyphal growth is however essential for successful leaf infection. A T-DNA mutagenesis screen performed on haploid spores identified a mutant, which can undergo yeast-like growth but cannot switch to hyphal growth. For this reason the mutant was non-pathogenic towards wheat leaves. The gene affected, MgAlg2, encoded a homologue of Saccharomyces cerevisiae ScAlg2, an alpha-1,2-mannosyltransferase, which functions in the early stages of asparagine-linked protein (N-) glycosylation. Targeted gene deletion and complementation experiments confirmed that loss of MgAlg2 function prevented the developmental growth switch. MgAlg2 was able to functionally complement the S. cerevisiae ScAlg2-1 temperature sensitive growth phenotype. Spores of ΔMgAlg2 mutants were hypersensitive to the cell wall disrupting agent Calcofluor white and produced abnormally hypo-N-glycosylated proteins. Gene expression, proteome and glycoproteome analysis revealed that ΔMgAlg2 mutant spores show responses typically associated with the accumulation of mis-folded proteins. The data presented highlight key roles for protein N-glycosylation in regulating the switch to hyphal growth, possibly as a consequence of maintaining correct folding and localization of key proteins involved in this process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Ascomycota / growth & development
  • Ascomycota / metabolism*
  • Ascomycota / pathogenicity
  • Gene Deletion
  • Gene Expression Profiling
  • Genetic Complementation Test
  • Glycosylation
  • Hyphae / growth & development
  • Hyphae / metabolism*
  • Hyphae / pathogenicity
  • Mannosyltransferases / genetics
  • Mannosyltransferases / metabolism*
  • Molecular Sequence Data
  • Mutagenesis, Insertional
  • Plant Diseases / microbiology*
  • Plant Leaves / microbiology
  • Proteome / analysis
  • Saccharomyces cerevisiae Proteins / genetics
  • Sequence Homology, Amino Acid
  • Triticum / microbiology*
  • Virulence
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*

Substances

  • Proteome
  • Saccharomyces cerevisiae Proteins
  • Virulence Factors
  • ALG2 protein, S cerevisiae
  • Mannosyltransferases