Abstract
Cytosolic free Ca^<2+> rise in various plant signal transduction pathways are postulated to be mediated by changes in membrane potential followed by activation of plasma membrane voltage-gated Ca^<2+> channels. However, molecular bases for the plasma membrane Ca^<2+> influx and their regulation in plant growth, development and stress responses remain largely unknown. We have identified a putative voltage-gated Ca^<2+> channel in rice. It was ubiquitously expressed in calli, mature leaves, shoots and roots. Overexpression of the gene restored growth rate of a yeast Ca^<2+>-requiring mutant cch1. To elucidate its physiological roles, we generated transgenic rice plants overexpressing its mRNA. Suspension-cultured overexpressing cells showed higher growth rate under Ca^<2+> limitation but the growth of overexpressing plants was remarkably slower under normal condition. A retrotransposon (Tos17) insertional mutant of the gene was isolated. Growth of the knockout cultured cells was less sensitive to extracellular [Ca^<2+>]. Possible physiological roles of the voltage-gated Ca^<2+> channel in growth regulation and stress signaling will be discussed.
