ARP2/3 complex-mediated actin dynamics is required for hydrogen peroxide-induced stomatal closure in Arabidopsis

Multiple cellular events like dynamic actin reorganization and hydrogen peroxide (H2O2) production were demonstrated to be involved in abscisic acid (ABA)-induced stomatal closure. However, the relationship between them as well as the underlying mechanisms remains poorly understood. Here, we showed that H2O2 generation is indispensable for ABA induction of actin reorganization in guard cells of Arabidopsis that requires the presence of ARP2/3 complex. H2O2-induced stomatal closure was delayed in the mutants of arpc4 and arpc5, and the rate of actin reorganization was slowed down in arpc4 and arpc5 in response to H2O2, suggesting that ARP2/3-mediated actin nucleation is required for H2O2-induced actin cytoskeleton remodelling. Furthermore, the expression of H2O2 biosynthetic related gene AtrbohD and the accumulation of H2O2 was delayed in response to ABA in arpc4 and arpc5, demonstrating that misregulated actin dynamics affects H2O2 production upon ABA treatment. These results support a possible causal relation between the production of H2O2 and actin dynamics in ABA-mediated guard cell signalling: ABA triggers H2O2 generation that causes the reorganization of the actin cytoskeleton partially mediated by ARP2/3 complex, and ARP2/3 complex-mediated actin dynamics may feedback regulate H2O2 production.