ACTIN DEPOLYMERIZING FACTOR4 regulates actin dynamics during innate immune signaling in Arabidopsis

Area of Science:

• Plant immunity
• Cell biology
• Molecular signaling

Background:

• Microbe-associated molecular patterns (MAMPs) are recognized by pattern recognition receptors (PRRs) in plants and animals, initiating innate immune responses.
• MAMP perception typically leads to actin cytoskeletal rearrangements, but the underlying signaling pathways are poorly understood.

Purpose of the Study:

• To investigate the regulation of actin dynamics during plant innate immune signaling at high spatial and temporal resolution.
• To elucidate the role of actin depolymerizing factors in MAMP-induced cytoskeletal remodeling.

Main Methods:

• Development of a high-resolution system to observe actin dynamics in plant epidermal cells.
• Treatment of cells with bacterial and fungal MAMPs.
• Analysis of actin remodeling in wild-type and ACTIN DEPOLYMERIZING FACTOR4 (ADF4) knockout mutant plants.

Main Results:

• MAMP perception rapidly altered single actin filament turnover within minutes.
• MAMP-induced actin changes mimicked the phenotype of an ADF4 knockout mutant.
• The adf4 mutant showed impaired responses to a bacterial MAMP (elf26) but retained responses to a fungal MAMP (chitin).

Conclusions:

• Actin depolymerizing factor (ADF) activity inhibition is a key regulator of actin remodeling during plant innate immune signaling.
• This study provides the first direct link between ADF/cofilin proteins and MAMP-triggered cytoskeletal rearrangements in plant cells.