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The PEX7-mediated peroxisomal import system is required for fungal development and pathogenicity in Magnaporthe

Jaeduk Goh1, Junhyun Jeon, Kyoung Su Kim

  • 1Department of Agricultural Biotechnology, Center for Fungal Genetic Resources, Plant Genomics and Breeding Institute, Seoul National University, Seoul, Korea.

Plos One
|December 24, 2011
PubMed

Insights

The peroxisomal targeting signal 2 (PTS2) receptor, MoPEX7, is crucial for the fungal pathogen Magnaporthe oryzae. Its disruption impairs fungal development and pathogenicity by affecting peroxisomal protein import and lipid metabolism.

Area of Science:

  • Plant pathology
  • Mycology
  • Cell biology

Background:

  • Peroxisomes are vital organelles in eukaryotic cells, involved in various metabolic processes.
  • Peroxisomal functions are known to influence pathogenicity in phytopathogenic fungi, but specific mechanisms remain elusive.
  • The import of matrix proteins into peroxisomes is mediated by targeting signals like PTS2.

Purpose of the Study:

  • To investigate the role of peroxisomal protein import via PTS2 in the development and pathogenicity of the rice blast fungus, Magnaporthe oryzae.
  • To elucidate the function of the PTS2 receptor gene, MoPEX7, in M. oryzae.

Main Methods:

  • Isolation and characterization of a pathogenicity-defective mutant using Agrobacterium tumefaciens-mediated transformation.
  • Gene disruption of the MoPEX7 gene in M. oryzae.
  • Analysis of peroxisomal protein import by examining the localization of a PTS2-containing thiolase (MoTHL1).
  • Assessment of fungal growth, development (conidiation), and pathogenicity assays on host plants.

Main Results:

  • Disruption of MoPEX7 abolished the peroxisomal import of MoTHL1, confirming MoPEX7's role in the PTS2 import pathway.
  • The ΔMopex7 mutant exhibited significantly reduced mycelial growth on fatty acids and impaired conidiophore/conidia production.
  • While conidial germination and appressoria formation were normal, ΔMopex7 conidia failed to cause disease, except in wounded tissues.
  • Defective appressoria in ΔMopex7 showed impaired turgor generation due to delayed lipid degradation and increased cell wall porosity.

Conclusions:

  • The MoPEX7-mediated peroxisomal protein import system is essential for the vegetative growth and development of M. oryzae.
  • Proper peroxisomal function, regulated by MoPEX7, is critical for M. oryzae pathogenicity, particularly for appressorial function and host cell penetration.
  • This study highlights the importance of peroxisomal matrix protein import in fungal pathogenesis.

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