A phase-separated nuclear GBPL circuit controls immunity in plants.

Area of Science:

• Cellular Biology
• Plant Science
• Biochemistry

Background:

• Liquid-liquid phase separation (LLPS) is crucial for organizing cellular activities within membraneless organelles.
• Plant immunity relies on complex molecular mechanisms to detect and respond to pathogens.

Purpose of the Study:

• To identify and characterize novel proteins involved in plant defense mechanisms.
• To elucidate the role of LLPS in nuclear compartmentalization during plant immune responses.

Main Methods:

• Identification of guanylate-binding protein (GBP)-like GTPases (GBPLs) in Arabidopsis thaliana.
• In situ cryo-electron tomography to visualize nuclear condensates.
• Biochemical assays to study protein-protein interactions and transcriptional regulation.

Main Results:

• GBPL1 and GBPL3 proteins drive the formation of GBPL defense-activated condensates (GDACs) through LLPS in the nucleus upon biotic stress.
• GBPL1 sequesters GBPL3 under basal conditions, but GBPL3 LLPS is triggered by immune cues.
• GDACs recruit transcriptional coactivators and RNA polymerase II to defense gene promoters, reprogramming gene expression for disease resistance.

Conclusions:

• GBPLs form a novel defense circuit in plants, utilizing LLPS to create functional nuclear condensates.
• These GBPL-mediated condensates are essential for mounting effective transcriptional defense responses against pathogens.