A jasmonate-mediated MAPK cascade regulates rice structural defense against brown planthoppers

Area of Science:

• Plant Biology
• Molecular Signaling
• Plant Defense Mechanisms

Background:

• Mitogen-activated protein kinase (MAPK) cascades are crucial for plant environmental stress responses.
• The specific MAPK components and mechanisms involved in plant defense against herbivores are not fully understood.
• Jasmonate (JA) signaling plays a key role in plant defense responses.

Purpose of the Study:

• To investigate the biological function and regulatory mechanisms of a herbivore-induced MAPK cascade in rice.
• To identify the specific MAPK components involved in rice defense against the brown planthopper (BPH).
• To elucidate how this MAPK cascade contributes to physical defense enhancement.

Main Methods:

• Transcriptional activation assays
• Genetic analysis of MAPK components
• Protein-protein interaction studies
• Comparative transcriptome analysis
• Chemical quantification of defense compounds

Main Results:

• Identified three tandemly arrayed MAPK kinase kinase (MKKK) genes (MKKK55, MKKK62, MKKK70) upregulated by BPH infestation.
• These MKKK genes are transcriptionally regulated by MYC2, a core regulator of JA signaling in rice.
• The identified MAPK cascade (MYC2-MKKK55/62/70-MKK3-MPK7/14) enhances rice physical defenses by increasing cellulose deposition, mediated by regulating cellulose synthase genes.
• Mutations in cascade components led to increased rice susceptibility to BPH.

Conclusions:

• The MYC2-MKKK55/62/70-MKK3-MPK7/14 module is a critical component of JA-dependent rice defense against herbivores.
• This MAPK cascade enhances physical plant defenses through modulation of cell wall composition.
• The study provides insights into the molecular mechanisms underlying plant-herbivore interactions.