57. 植物のストレス応答・発生シグナル伝達におけるCa^<2+>チャネルTPCファミリーの生理機能

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To elucidate physiological roles of the TPC1 family, putative voltage-gated Ca^<2+> channels, we generated and characterized overexpressors (OX) and a retrotransposon-insertional knockout (KO) mutant. The OX cells showed hypersensitivity to excess Ca^<2+> but higher growth rate under Ca^<2+> limitation, while growth of the KO cells was less sensitive to [Ca^<2+>]_<ext>, suggesting that OsTPC1 has Ca^<2+> transport activity across the plasma membrane. The OX plants showed reduced growth and abnormal greening of roots. These results suggest that OsTPC1 functions as a Ca^<2+>-permeable channel involved in the regulation of growth and development. Cosuppression of NtTPC1s in apoaequorin-expressing tobacco BY-2 cells resulted in inhibition of [Ca^<2+>]_<cyt> rise in response to sucrose and a pathogenic elicitor, while did not affect hypoosmotic shock-induced [Ca^<2+>]_<cyt> increase. Cosuppression of NtTPC1s also caused suppression of elicitor-induced PCD and defense-related gene expression. OsTPC1 OX cells showed enhanced sensitivity to an elicitor to induce oxidative burst, activation of a MAP kinase, OsMPK2, as well as PCD. In contrast, a series of defense responses including PCD and MAPK activation were severely suppressed in the KO cells, which was complemented by overexpression of the wild-type gene. These results suggest that the TPC family determines sensitivity to the elicitor and plays a role as a key regulator of elicitor-induced defense responses, activation of MAPK cascade and PCD.
2005-10-13

57. 植物のストレス応答・発生シグナル伝達におけるCa^<2+>チャネルTPCファミリーの生理機能

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