Rising Star: A Unified Mechanism of Plant NLR Immune Signaling

Area of Science:

• Plant Immunity
• Molecular Biology
• Biochemistry

Background:

• Nucleotide-binding leucine-rich repeat (NLR) proteins are crucial plant immune receptors.
• NLRs detect pathogen effectors and trigger effector-triggered immunity (ETI).
• The conserved immune responses despite diverse recognition mechanisms remained a puzzle.

Purpose of the Study:

• To elucidate the molecular mechanism of plant immune receptor activation and signaling.
• To investigate the structural basis of NLR function in plant defense.
• To understand how diverse NLRs elicit conserved immune responses.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of activated NLRs.
• Biochemical assays to analyze protein complex formation and enzymatic activity.
• Functional studies to assess calcium ion channel activity and signaling.

Main Results:

• The coiled-coil NLR (CNL) ZAR1 forms a pentameric resistosome with Ca2+-permeable ion channel activity.
• TIR-domain NLRs (TNLs) form resistosomes and function as NADases, generating signals.
• Helper NLRs also assemble into Ca2+-conducting resistosomes, linking diverse NLRs to Ca2+ influx.

Conclusions:

• A unified mechanism for plant immunity involving NLR resistosome formation and Ca2+ influx is established.
• Resistosome assembly is a conserved feature across different NLR subclasses.
• This work reshapes the understanding of plant innate immunity and NLR function.