ROP to PA Pathway for ROS Regulation

Abstract

The response of plants to stressful conditions, such as pathogen infection or wounding, often includes the generation of reactive oxygen species (ROS). Because levels of phosphatidic acid (PA) increase during a number of stress conditions, this lipid has been implicated in regulating ROS production. Park et al. report that the PA-regulated response in Arabidopsis involves a small guanosine triphosphatase called Rho-related small G protein in plants (ROP). Liposomes containing PA induced cell death when infiltrated into isolated Arabidopsis leaves. Exposure to PA metabolites or other phospholipids had no effect. PA treatment of cultured guard cells or addition of purified recombinant ROP2 to leaf extracts boosted ROS production. Leaves from transgenic Arabidopsis plants expressing a constitutively active form of ROP2 were more sensitive to PA exposure, showing earlier symptoms of cell death compared with wild-type leaves. In contrast, less ROS was generated in response to PA in leaves having a dominant-negative form of ROP2. Although the study places ROP2 in the PA-ROS pathway, activated ROP2 by itself did not induce ROS production or cell death. The authors suggest that PA acts downstream of activated ROP and that the direct target PA remains to be determined. J. Park, Y. Gu, Y. Lee, Z. Yang, Y. Lee, Phosphatidic acid induces leaf cell death in Arabidopsis by activating the Rho-related small G protein GTPase-mediated pathway of reactive oxygen species generation. Plant Physiol. 134 , 129-136 (2004). [Abstract] [Full Text]