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A rice fungal MAMP-responsive MAPK cascade regulates metabolic flow to antimicrobial metabolite synthesis

Mitsuko Kishi-Kaboshi1, Kazunori Okada, Leona Kurimoto

  • 1Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.

The Plant Journal : for Cell and Molecular Biology
|June 8, 2010
PubMed

Insights

The OsMKK4-OsMPK6 pathway in rice is crucial for plant defense against fungal pathogens. This signaling cascade reprograms plant metabolism, enhancing the production of antimicrobial compounds like diterpenoid phytoalexins.

Area of Science:

  • Plant immunity
  • Molecular signaling
  • Plant biochemistry

Background:

  • Plants defend against microbial pathogens using pattern recognition receptors that detect microbial-associated molecular patterns (MAMPs).
  • Mitogen-activated protein kinase (MAPK) cascades are key signal integrators in MAMP-triggered immunity, but downstream pathways remain unclear.
  • Understanding these pathways is vital for enhancing crop resistance to diseases.

Purpose of the Study:

  • To elucidate the signaling pathway from MAPK cascades to defense responses in rice upon MAMP perception.
  • To investigate the role of the OsMKK4-OsMPK6 cascade in mediating chitin elicitor-induced defense mechanisms.

Main Methods:

  • Investigated the activation of rice MAPKs (OsMPK3, OsMPK6) and MAPK kinase (OsMKK4) by chitin elicitor.
  • Utilized conditional expression of an active form of OsMKK4 (OsMKK4(DD)) to study downstream effects.
  • Analyzed gene expression, metabolic changes, cell death, and phytoalexin biosynthesis.

Main Results:

  • The OsMKK4-OsMPK6 cascade is activated by chitin elicitor, with OsMPK6 being essential for diterpenoid phytoalexin biosynthesis.
  • OsMKK4(DD) expression induced significant gene expression alterations, shifting metabolism towards secondary metabolites and suppressing basic cellular processes.
  • OsMKK4(DD) triggered cell death and diterpenoid phytoalexin/lignin biosynthesis, dependent on OsMPK6, but not extracellular ROS generation.

Conclusions:

  • The OsMKK4-OsMPK6 signaling cascade is a critical regulator of MAMP-triggered plant defense responses in rice.
  • This cascade plays a pivotal role in reprogramming plant metabolism to prioritize defense over growth and basic cellular functions.
  • The findings provide insights into the molecular mechanisms underlying plant immunity and potential targets for crop improvement.

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