The MAP Kinase Bbslt2 Controls Growth, Conidiation, Cell Wall Integrity, and Virulence in the Insect Pathogenic Fungus Beauveria Bassiana

Fungal Genet Biol. 2012 Jul;49(7):544-55. doi: 10.1016/j.fgb.2012.05.002. Epub 2012 May 12.

Abstract

Entomopathogenic fungi, such as Beauveria bassiana, are key environmental pathogens of insects that have been exploited for biological control of insect pests. Mitogen-activated protein (MAP) kinases play crucial roles in regulating fungal development, growth, and pathogenicity, mediating responses to the environment. Bbslt2, encoding for an Slt2 family MAPK, was isolated and characterized from B. bassiana. Gene disruption of Bbslt2 affected growth, caused a significant reduction in conidial production and viability, and increased sensitivity to Congo Red and fungal cell wall degrading enzymes. ΔBbslt2 mutants were altered in cell wall structure and composition, which included temperature dependent chitin accumulation, reductions in conidial and hyphal hydrophobicity, and alterations in cell surface carbohydrate epitopes. The ΔBbslt2 strain also showed hypersensitivity to heat shock and altered trehalose accumulation, which could only be partially attributed to changes in the expression of trehalase (ntl1). Insect bioassays revealed decreased virulence in the ΔBbslt2 strain using both topical and intrahemoceol injection assays. These results indicate that Bbslt2 plays an important role in conidiation, viability, cell wall integrity and virulence in B. bassiana. Our findings are discussed within the context of the two previous MAP kinases characterized from B. bassiana.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antifungal Agents / toxicity
  • Beauveria / enzymology*
  • Beauveria / genetics*
  • Beauveria / growth & development
  • Beauveria / pathogenicity
  • Biological Assay
  • Cell Wall / chemistry
  • Cell Wall / metabolism*
  • Cell Wall / ultrastructure
  • Congo Red / toxicity
  • DNA, Fungal / chemistry
  • DNA, Fungal / genetics
  • Gene Deletion
  • Gene Expression Regulation, Fungal*
  • Insecta
  • Microbial Viability
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism*
  • Molecular Sequence Data
  • Sequence Analysis, DNA
  • Spores, Fungal / growth & development*
  • Survival Analysis
  • Virulence

Substances

  • Antifungal Agents
  • DNA, Fungal
  • Congo Red
  • Mitogen-Activated Protein Kinases

Associated data

  • GENBANK/JF932502
  • GENBANK/JF932503