Calcium Channel Regulation in Arabidopsis Guard Cells

Duke University, Durham NC

Investigators

Abstract

Drought stress is a major limitation for agricultural production. More than 95% of water loss from plants occurs via stomatal pores, which are formed by pairs of guard cells in the leaf epidermis. Stomata open and close in response to various environmental signals, such as light, CO2 and water status. A signaling network in guard cells integrates these signals to regulate stomatal movements, which control water loss and CO2 uptake. The long-term goal of the project is to dissect this signaling network by studying Ca2+ channels, which have been proposed to play a key role. Elevation of cytosolic free Ca2+ concentrations in guard cells is an early event during abscisic acid-triggered stomatal closing. Ion channel-mediated Ca2+ influx gives rise to the cytosolic Ca2+ increase. It has been shown previously that hydrogen peroxide activates Ca2+ channels in the plasma membrane of guard cells. Inhibition of NADPH oxidase prevents H2O2 production and reduces abscisic acid-induced stomatal closing. Additionally, preliminary studies have revealed that nitric oxide also triggers stomatal closure. This project will further study H2O2 and nitric oxide regulation of the Ca2+ channels via a combined cell biological, biophysical, and molecular genetic approach. The effects of biologically active oxidants and antioxidants on the Ca2+ channels will be analyzed. Furthermore, the role of NADPH oxidase in guard cell abscisic acid signaling will be determined. The effects of nitric oxide on stomatal movements will also be examined. The information gained in the project will provide insight into the guard cell signaling network and contribute to the identification of potential molecular and genetic targets for engineering drought-resistant plants. Furthermore, the project may also impact on the understanding of how nitric oxide, a major air pollutant, affects the global ecosystem via plants.