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

• Published in: Molecular microbiology 2011-07, Vol.81 (2), p.415-433
• Main Authors: Motteram, Juliet, Lovegrove, Alison, Pirie, Elizabeth, Marsh, Justin, Devonshire, Jean, van de Meene, Allison, Hammond‐Kosack, Kim, Rudd, Jason J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Ascomycetes; Ascomycota - growth & development; Ascomycota - metabolism; Ascomycota - pathogenicity; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Fungi; Gene Deletion; Gene expression; Gene Expression Profiling; Genetic Complementation Test; Glycosylation; Hyphae - growth & development; Hyphae - metabolism; Hyphae - pathogenicity; Mannosyltransferases - genetics; Mannosyltransferases - metabolism; Microbiology; Miscellaneous; Molecular Sequence Data; Mutagenesis; Mutagenesis, Insertional; Mycology; Mycosphaerella graminicola; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - microbiology; Plant Leaves - microbiology; Proteins; Proteome - analysis; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins - genetics; Septoria tritici; Sequence Homology, Amino Acid; Triticum - microbiology; Triticum aestivum; Virulence; Virulence Factors - genetics; Virulence Factors - metabolism
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2011.07701.x

Summary 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.