The roles of anion channels in Arabidopsis immunity.

Anion efflux is one of the most immediate responses of plant cells to pathogen attacks, suggesting that anion channels may play a role in plant defense. Recently we reported that the chloride channel AtCLCd negatively regulates Arabidopsis pathogen-associated molecular pattern-triggered immunity (PTI), probably by affecting trafficking of the pattern recognition receptors (PRRs). Since AtCLCd is localized to the trans-Golgi network, it is not likely to be directly involved in anion flux across the plasma membrane. Here, we used a pharmacological approach to explore further the function of plasma membrane-localized R-type and S-type anion channels in plant immunity. We found that the R-type and S-type anion channels play opposite roles in Arabidopsis innate immunity. Inhibition of the R-type anion channels enhances, whereas inhibition of the S-type channels inhibits PTI and effector-triggered immunity (ETI).