NLRs guard metabolism to coordinate pattern- and effector-triggered immunity

Area of Science:

• Plant immunity
• Molecular plant-pathogen interactions
• Plant biochemistry

Background:

• Plant immune responses, including pattern-triggered immunity (PTI) and effector-triggered immunity (ETI), involve defense metabolites.
• The coordination between immune receptors, defense metabolite production, and broad-spectrum resistance is not fully understood.

Purpose of the Study:

• To identify key regulators of defense metabolite production in rice (Oryza sativa) for both PTI and ETI.
• To elucidate the molecular mechanisms linking immune receptors to defense pathways and broad-spectrum resistance.

Main Methods:

• Identification and characterization of the deubiquitinase PICI1 in rice.
• Analysis of PICI1's role in stabilizing methionine synthetases and regulating methionine-mediated immunity.
• Investigating the interaction between PICI1, blast fungal effectors (e.g., AvrPi9), and plant immune receptors (NLRs like PigmR).
• Examining natural variation in the PICI1 gene and its impact on rice blast resistance.

Main Results:

• PICI1 acts as an immunity hub, deubiquitinating and stabilizing methionine synthetases to promote methionine-mediated immunity via ethylene biosynthesis.
• Blast fungal effectors target PICI1 for degradation to suppress PTI.
• Plant NLRs (e.g., PigmR) protect PICI1 from effector-mediated degradation, reactivating the immune response.
• Natural variation in PICI1 contributes to differences in blast resistance between rice subspecies.

Conclusions:

• NLRs engage in an evolutionary arms race with effectors, utilizing a competitive mechanism centered on the PICI1-mediated metabolic pathway.
• This pathway synchronizes PTI and ETI, ensuring broad-spectrum resistance in rice.