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Updated: Aug 31, 2026

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea
07:14

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea

Published on: August 4, 2018

The G-beta subunit MGB1 is involved in regulating multiple steps of infection-related morphogenesis in Magnaporthe

Marie Nishimura1, Gyungsoon Park, Jin-Rong Xu

  • 1National Institute of Agrobiological Sciences, 2-1-2, Kan' non dai, Tsukuba, Ibaraki, 305-8602, Japan.

Molecular Microbiology
|September 26, 2003
PubMed

Insights

The G protein beta subunit (MGB1) in Magnaporthe grisea is crucial for fungal development and infection. MGB1 regulates cyclic AMP (cAMP) signaling, impacting conidiation and appressorium formation for rice blast disease.

Area of Science:

  • Molecular Biology
  • Mycology
  • Plant Pathology

Background:

  • Trimeric G-proteins are key signal transducers in eukaryotes.
  • In Magnaporthe grisea, the Pmk1 MAP kinase pathway is vital for infection, but its upstream regulation is unclear.
  • G-alpha subunit mutants differ phenotypically from pmk1 mutants, suggesting G-beta involvement in Pmk1 activation.

Purpose of the Study:

  • To isolate and characterize the gene encoding the G-protein beta subunit (MGB1) in M. grisea.
  • To elucidate the role of MGB1 in fungal development, signaling, and pathogenicity.
  • To investigate the relationship between MGB1, cAMP levels, and the Pmk1 pathway.

Main Methods:

  • Gene isolation and characterization of MGB1.
  • Generation and phenotypic analysis of MGB1 deletion mutants.
  • Assessment of conidiation, appressorium formation, and plant penetration.
  • Measurement of intracellular cAMP levels.
  • Complementation studies and analysis of MGB1 overexpression transformants.

Main Results:

  • MGB1 disruption reduced conidiation and impaired appressorium formation and rice leaf penetration.
  • MGB1 mutants exhibited reduced intracellular cAMP levels, with partial rescue by exogenous cAMP.
  • Exogenous cAMP induced abnormal appressoria in mgb1 mutants, indicating a role in cAMP signaling.
  • MGB1 overexpression enhanced appressorium formation on hydrophilic surfaces.
  • MGB1 appears to regulate cAMP signaling for conidiation and surface sensing.

Conclusions:

  • MGB1 is essential for regulating conidiation, surface recognition, and appressorium formation in M. grisea.
  • MGB1 likely functions upstream of the Pmk1 MAP kinase pathway, mediating cAMP signaling for infection.
  • MGB1 plays a critical role in the pathogenicity of the rice blast fungus.

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