Intracellular Ca2+ Messenger System in Plants

Abstract

Publisher Summary This chapter reviews the intracellular Ca2+ messenger system in plant cells. It describes the unique features of plants in signal transduction. Changes in cytoplasmic free Ca2+ concentration modify many physiological processes in plants. Ca2+ plays a vital role as a second messenger in intracellular signaling. The cytoplasmic Ca2+ concentration is maintained at a low level by active extracellular extrusion and sequestration to intracellular organelles. When cells are stimulated, influx of extracellular Ca2+ or efflux of Ca2+ sequestrated in organelles occur leading to an increase in cytoplasmic Ca2+ concentration. These Ca2+ fluxes are considered to be mediated by ion channels. In plant cells, Ca2+ appears to be central in signal transduction, whereas the cAMP messenger system is lacking. The initial step of signal transduction is perception or recognition of the signal by a specific receptor on the membrane. GTP-binding proteins (G proteins) are central to the transduction of many receptor signals in animal cells. They are a highly conserved family of heterotrimeric membrane-associated proteins composed of α, β, and γ subunits (Gα, Gβ, and Gγ). The fundamental role of G protein in Ca2+ signaling may be the activation of the Ca2+ channel and phospholipase C on the plasma membrane, which subsequently leads to an increase in cytoplasmic Ca2+ concentration.