Flg22-induced Ca²⁺ increases undergo desensitization and resensitization.

Area of Science:

• Plant immunology
• Molecular plant pathology
• Calcium signaling

Background:

• Pathogen-associated molecular patterns (PAMPs) like flagellin epitope flg22 trigger plant immune responses via the receptor FLAGELLIN SENSING2 (FLS2).
• PAMP-triggered immunity involves calcium influx (FICA) and reactive oxygen species (ROS) burst, which undergo adaptation (desensitization and resensitization) to prevent over-responses.
• The adaptation mechanisms of FICA are not well understood.

Purpose of the Study:

• To systematically analyze the adaptation mechanisms of flg22-induced increases in cytosolic Ca2+ concentration (FICA) in Arabidopsis thaliana.
• To characterize the kinetics of FICA desensitization and resensitization upon successive flg22 treatments.
• To investigate the molecular players involved in FICA adaptation.

Main Methods:

• Two successive flg22 treatments were applied to Arabidopsis thaliana.
• Cytosolic Ca2+ concentration ([Ca2+]i) increases (FICA) were recorded and analyzed.
• Pharmacological approaches were used to investigate the roles of FLS2 endocytosis, PM depolarization, and de novo protein synthesis in FICA adaptation.

Main Results:

• FICA exhibited rapid desensitization and slow resensitization following sequential flg22 stimulation.
• Rapid FICA desensitization appears to be regulated by ligand-induced FLS2 endocytosis and PM depolarization.
• FICA resensitization requires de novo FLS2 protein synthesis and is slower than FLS2 protein recovery, suggesting involvement of other regulatory components.

Conclusions:

• FICA sensitivity adaptation is crucial for appropriate plant immune responses to pathogens.
• The study defines the adaptation kinetics of FICA, highlighting rapid desensitization and slow resensitization.
• Further research into Ca2+-mediated adaptive mechanisms in PAMP-triggered immunity is warranted.