CPMK2, an SLT2‐homologous mitogen‐activated protein (MAP) kinase, is essential for pathogenesis of Claviceps purpurea on rye: evidence for a second conserved pathogenesis‐related MAP kinase cascade in phytopathogenic fungi

Abstract

SummaryCpmk2 , encoding a mitogen-activated protein (MAP) kinase from the ascomycete Claviceps purpurea , is an orthologue of SLT2 from Saccharomyces cerevisiae , the first isolated from a biotrophic, nonappressorium-forming pathogen. Deletion mutants obtained by a gene replacement approach show impaired vegetative properties (no conidiation) and a significantly reduced virulence, although they retain a limited ability to colonize the host tissue. Increased sensitivity to protoplasting enzymes indicates that the cell wall structure of the mutants may be altered. As the phenotypes of these mutants are similar to those observed in strains of the rice pathogen, Magnaporthe grisea , that have been deprived of their MAP kinase gene mps1 , the ability of cpmk2 to complement the defects of D D D D mps1 was investigated. Interestingly, the C. purpurea gene, under the control of its own promoter, was able to complement the M. grisea mutant phenotype: transformants were able to sporulate and form infection hyphae on onion epidermis and were fully pathogenic on barley leaves. This indicates that, despite the differences in infection strategies, which include host and organ specificity, mode of penetration and colonization of host tissue, CPMK2 / MPS1 defines a second MAP kinase cascade (after the Fus3p/PMK1 cascade) essential for fungal pathogenicity.

The Nuclear Dbf2-Related Kinase COT1 and the Mitogen-Activated Protein Kinases MAK1 and MAK2 Genetically Interact to Regulate Filamentous Growth, Hyphal Fusion and Sexual Development in Neurospora crassa

“…Even though mutants in the MAPK homologous to yeast Slt2 have been generated in A. nidulans, and in several phytopathogenic fungi (Xu et al 1998;Bussink and Osmani 1999;Hou et al 2002;Kojima et al 2002;Mey et al 2002), information concerning this third MAPK pathway in filamentous fungi is still limited. Common phenotypes of Slt2-like kinase mutants included altered cell walls and defects in conidial germination (which could be remedied by high-osmolarity media) and autolysis in central areas of the colony, suggesting the involvement of a cell-integrity-type MAPK pathway in filamentous fungi.…”

The Mitogen-Activated Protein Kinase Signal Transduction Pathways in Alternaria Species

“…As have been shown in C. lagenarium (Kojima et al, 2002), C. purpurea (Mey et al, 2002a), M. grisea (Xu et al, 1998) and B. cinerea (Rui and Hahn, 2007), the Slt2 pathway was also involved in conidiation in Alternaria. In A. alternata, deletion of AaSlt2 signiticantly reduced conidial formation, but did not affect the conidial germination.…”

“…As the primary function of Slt2 pathway, its homologs in many pathogenic fungi also had the role of maintaining cell wall integrity in M. grisea (Xu et al, 1998), Claviceps purpurea (Mey et al, 2002a), Aspergillus fumigates (Valiante et al, 2008), A. nidulans (Bussink and Osmani, 1999), F. graminearum (Hou et al, 2002) and M. graminicola (Mehrabi et al, 2006a). However, in B. cinerea, the Δbmp3 (Slt2 homologs) mutant and the wild-type showed no difference of protoplast release when treated with β-glucanase, the chitin synthase inhibitor Nikkomycin Z, and the cell-wall formation inhibitor Calcofluor-White (Rui and Hahn, 2007).…”

Mitogen-activated protein kinase signaling pathways of the tangerine pathotype of Alternaria alternata

“…purpurea, M. grisea, Fusarium graminearum or Aspergillus nidulans. [52][53][54][55][56] In contrast, Slt2 plays no roles in cell wall integrity in B. cinerea, Col. lagenarium or My. Graminicola.…”