Hydrogen Sulfide Disturbs Actin Polymerization via S-Sulfhydration Resulting in Stunted Root Hair Growth

Hydrogen sulfide (H 2 S) is an important signaling molecule in plants. Our previous report suggested that H 2 S signaling affects the actin cytoskeleton and root hair growth. However, the underlying mechanisms of its effects are not understood. S -Sulfhydration of proteins is regulated directly by H 2 S, which converts the thiol groups of cysteine (Cys) residues to persulfides and alters protein function. In this work, we studied the effects of S -sulfhydration on actin dynamics in Arabidopsis ( Arabidopsis thaliana ). We generated transgenic plants overexpressing the H 2 S biosynthesis-related genes l-CYSTEINE DESULFHYDRASE ( LCD ) and d-CYSTEINE DESULFHYDRASE in the O-acetylserine(thiol)lyase isoform a1 ( oasa1 ) mutant and Columbia-0 backgrounds. The H 2 S content increased significantly in overexpressing LCD / oasa1 plants. The density of filamentous actin (F-actin) bundles and the F-actin/globular actin ratio decreased in overexpressing LCD / oasa1 plants. S -Sulfhydration also was enhanced in overexpressing LCD / oasa1 plants. An analysis of actin dynamics suggested that S -sulfhydration inhibited actin polymerization. We also found that ACTIN2 (ACT2) was S -sulfhydrated at Cys-287. Cys-287 is adjacent to the D-loop, which acts as a central region for hydrophobic and electrostatic interactions and stabilizes F-actin filaments. Overaccumulation of H 2 S caused the depolymerization of F-actin bundles and inhibited root hair growth. Introduction of ACT2 carrying a Cys-287-to-Ser mutation into an act2-1 mutant partially suppressed H 2 S-dependent inhibition of root hair growth. We conclude that H 2 S regulates actin dynamics and affects root hair growth.