An Immune-Responsive Cytoskeletal-Plasma Membrane Feedback Loop in Plants

Area of Science:

• Plant biology
• Cellular immunology
• Cytoskeletal dynamics

Background:

• Cell wall appositions (CWAs) are plant immune structures that halt pathogen invasion by altering cell growth.
• The formation of CWAs requires coordinated plasma membrane (PM) invagination and barrier material export.
• The precise interplay between exocytosis, the cytoskeleton, and CWAs remains poorly understood.

Purpose of the Study:

• To investigate the role of actin dynamics in linking exocytosis and cytoskeletal organization during CWA formation.
• To elucidate the function of FORMIN4 in plant immune responses and cytoskeletal regulation at the PM.

Main Methods:

• Utilized Total Internal Reflection Fluorescence (TIRF) microscopy in Arabidopsis thaliana.
• Controlled induction of FORMIN4-green fluorescent protein (GFP) expression.
• Investigated actin-dependent trafficking and protein localization.

Main Results:

• Actin-dependent trafficking delivers membrane-integrated FORMIN4 to immune response sites.
• FORMIN4 accumulates in dynamic vesicular clusters at the PM.
• FORMIN4 deactivation impairs plant defense and alters filamentous actin (F-actin) distribution.
• FORMIN4 localizes stably, segregated from endosomal traffic, and spatially associates with PEN3.

Conclusions:

• FORMIN4 acts as a spatial feedback element in a multi-layered cytoskeletal response during CWA formation.
• Positional feedback by FORMIN4 influences F-actin distribution at the CWA boundary.
• This mechanism contributes to pre-invasion defense outcomes in plants.