Actin Dynamics Regulating The Activity Of NADPH Oxidase And The Generation Of Reactive Oxygen Species Under Salt Stress In Arabidopsis

Actin cytoskeleton plays important roles in many cellular processes that regulate plant growth and development. Acitn filaments are dynamic cytoarchitectures and the remodeling by assembly and disassembly of actin is required for its function. Actin dynamics are regulated by various actin-regulating proteins in cells. Furthermore the regulation of actin dynamics also is under the control of intracellular and extracellular signaling which function in the alteration of cell activities and the adaption to environmental stimuli. The actin dynamics regulating reactive oxygen species (ROS) generation remains to be established in plant cells although actin was found to be involved in AtrbohC localization in root hairs. In this study we found that actin dynamics were changed after 10 min treated with 200 mM NaCl and the changes of actin dynamics were correlated with ROS generation by regulating AtrbohC activity.(1) Obvious changes of actin dynamics were found after treated 10min with 200mM NaCl in the epidermal cells of the elongation zone of Arabidopsis root tip. In some cells the long actin bundles were fragmented. Although these short fragments still change their position they could not form longer filaments. More than 72% cells show these changes of actin dynamics. In other cells the actin filaments did not become fragments but the dynamics of actin disappeared except from the lateral migration(2) Actin dynamics regulating the ROS generation in root elongation zone under salt stress. We analyzed ROS generations in roots after treated with the actin-specific regent jasplakinolide (Jasp) and latrunculin B (Lat-B), and found that treatment with 10μM Lat-B increased obviously the ROS level in elongation zone of root after 10min treated with 200mM NaCl. Treatment with 0.14μM Jasp also enhanced the production of ROS in elongation zone. These results reveal that the actin dynamics are involved in regulating ROS level under salt stress and the disturbance of actin dynamics enhance the ROS generation under salt stress(3) AtrbohC was responsible for the actin-regulated ROS generation under salt stress. The salt-induced ROS level in the elongation zone was reduced after treated with 10μM DPI compared with that of the control. The mutants of AtrbohC all showed reduced ROS production after treated with 200mM NaCl and Lat-B pretreatment did not change the ROS level in elongation zone of mutants of AtrbohC. This result indicates that actin dynamics play its role by modulating AtrbohC activity in salt-induced ROS generation(4) Actin related-protein(ARP)2 involved in ROS generation in the elongation zone under salt stress. Salt-induced ROS level was increased in the elongation zone of arp2 mutants but not in arp3 mutant. This result indicates that ARP2 was involved in salt-induced ROS generationOur results reveal that actin dynamics is important for ROS generation by regulating NADPH oxidase AtrbohC activity under salt stress...