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Understanding the Development of Compensatory Pathways in a Mutant Malaria Parasite Harbouring Hypomorphic Allele of Plant-Like Kinases
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Two PAK kinase genes, CHM1 and MST20, have distinct functions in Magnaporthe grisea

Lei Li1, Chaoyang Xue, Kenneth Bruno

  • 1Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.

Molecular Plant-Microbe Interactions : MPMI
|May 15, 2004
PubMed

Insights

In Magnaporthe grisea, CHM1 is crucial for appressorium formation and penetration, while MST20 is dispensable for infection. These PAK genes may have redundant roles, but CHM1 is essential for rice blast fungus pathogenesis.

Area of Science:

  • Molecular biology
  • Plant pathology
  • Mycology

Background:

  • The Pmk1 mitogen-activated protein (MAP) kinase pathway is vital for rice blast fungus (Magnaporthe grisea) infection.
  • PAK kinases regulate MAP kinase pathways in other fungi, suggesting a similar role in M. grisea.

Purpose of the Study:

  • To isolate and characterize PAK genes (CHM1 and MST20) in M. grisea.
  • To investigate the roles of CHM1 and MST20 in fungal development and pathogenesis.

Main Methods:

  • Gene deletion and mutant characterization.
  • Phenotypic analysis of growth, conidiation, and appressorium formation.
  • Pathogenicity assays on rice plants.

Main Results:

  • MST20 mutants showed reduced aerial hyphae growth and conidiation but were otherwise normal.
  • CHM1 mutants exhibited defects in growth, conidiation, appressorium formation, and penetration, yet could colonize wounded leaves.
  • CHM1 mutants produced abnormal conidia and had reduced hyphal compartment length. Spontaneous sectors from CHM1 mutants remained defective in pathogenesis.

Conclusions:

  • MST20 is not essential for M. grisea plant infection.
  • CHM1 plays a critical role in appressorium formation and penetration, essential for pathogenesis.
  • CHM1 and MST20 may possess redundant functions, and neither appears individually critical for activating the Pmk1 MAP kinase pathway during infection stages.

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