A role for phosphatidylinositol 3-phosphate in abscisic acid-induced reactive oxygen species generation in guard cells.

Guard cells generate reactive oxygen species (ROS) in response to abscisic acid (ABA), which leads to stomatal closing. The upstream steps of the ABA-induced ROS generation pathway remain largely unknown. In animal cells, ROS generation in neutrophils is activated by phosphatidylinositol 3-phosphate (PI3P). Stomatal guard cells contain PI3P and PI 3-kinase activity. In this study, we tested whether PI3P has a role in ROS generation in guard cells exposed to ABA. We found that PI 3-kinase inhibitors wortmannin or LY294002 inhibited ABA-induced ROS generation and stomatal closing. Endosome-binding domain (of human EEA1), which specifically binds to PI3P, also inhibited ABA-induced ROS generation and stomatal closing when overexpressed in guard cells. Hydrogen peroxide partially reversed the effects of wortmannin or LY294002 on ABA-induced stomatal closing. These results support a role for PI3P in ABA-induced ROS generation and stomatal closing movement.