Identification of a putative voltage‐gated Ca2+ channel as a key regulator of elicitor‐induced hypersensitive cell death and mitogen‐activated protein kinase activation in rice

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Abstract
Summary: Elicitor‐triggered transient membrane potential changes and Ca2+ influx through the plasma membrane are thought to be important during defense signaling in plants. However, the molecular bases for the Ca2+ influx and its regulation remain largely unknown. Here we tested effects of overexpression as well as retrotransposon (Tos17)‐insertional mutagenesis of the rice two‐pore channel 1 (OsTPC1), a putative voltage‐gated Ca2+‐permeable channel, on a proteinaceous fungal elicitor‐induced defense responses in rice cells. The overexpressor showed enhanced sensitivity to the elicitor to induce oxidative burst, activation of a mitogen‐activated protein kinase (MAPK), OsMPK2, as well as hypersensitive cell death. On the contrary, a series of defense responses including the cell death and activation of the MAPK were severely suppressed in the insertional mutant, which was complemented by overexpression of the wild‐type gene. These results suggest that the putative Ca2+‐permeable channel determines sensitivity to the elicitor and plays a role as a key regulator of elicitor‐induced defense responses, activation of MAPK cascade and hypersensitive cell death.