Physiological Roles of a Putative Voltage-Gated Ca²⁺ Channel, OsTPC1, in Stress Signal Transduction and Regulation of Programmed Cell Death in Rice.

Abstract

To reveal the molecular mechanisms and physiological roles of stress-induced Ca²⁺ mobilization, we established the retrotransposon-insertional knockout lines as well as the overexpressing lines of a putative voltage-gated Ca²⁺ permeable channel, OsTPC1, in rice (PCP 2004). The Ostpc1 overexpressor showed enhanced sensitivity to a proteinaceous elicitor, whereas the elicitor-induced defense responses including gene expression were strongly suppressed in the knockout cells, which was rescued by expression of Ostpc1 (Plant J. 2005). We have established a noninvasive monitoring system of cytosolic Ca²⁺ concentration both in planta and in suspension-cultured cells. Elicitor-induced gene expression profile as well as changes in the cytosolic Ca²⁺ concentration induced by various stresses are comparatively analyzed between the Ostpc1 knockout and the wild type lines. Possible physiological roles of OsTPC1 in stress-induced Ca²⁺ mobilization, gene expression and defense responses including programmed cell death will be discussed.