External-calcium Signal Transduction in Arabidopsis Guard Cells

Duke University, Durham NC

Investigators

Abstract

The perception of environmental signals is crucial for various physiological and developmental processes in plants. It is well established that external signals trigger cytosolic free Ca2+ increases in plant cells. However, the molecular components governing these cytosolic Ca2+ changes are poorly understood. The Arabidopsis extracellular Ca2+ (Ca2+o)-sensing receptor (CAS) may represent the only cell-surface receptor cloned so far that has been shown to convert an external stimulus into cytosolic Ca2+ increases in plants. CAS plays an essential role in Ca2+o-induced closing of stomatal pores, which are formed by pairs of guard cells in leaf surface. The long-term goal of this project is to understand the molecular mechanisms of Ca2+o signal transduction in guard cells. In this project, experiments will be carried out to (1) identify Ca2+-binding sites in the CAS N-terminus by site-directed and deletion mutation; (2) confirm Ca2+o activation of CAS triggering Ca2+ release using heterologous expression systems and initiate a screen for Arabidopsis inositol 1,4,5-trisphosphate (IP3) receptor; and (3) identify the molecular components downstream of CAS through complex purification. This project will not only further understanding of guard cell Ca2+o signaling but also shed light on the Ca2+ machineries governing external-signal perception in plants. The broader impacts of this project will include teaching and training of the next generation of scientists at the postdoctoral, graduate, and undergraduate levels.