Abstract
Ca 2+ is the pivotal second messenger for induction of defense responses induced by treatment of pathogen-derived elicitor or microbial infection in plants. However, molecular bases for elicitor-induced generation of Ca 2+ signals (Ca 2+ transients) are largely unknown. We here identified cDNAs for putative voltage-dependent Ca 2+-permeable channels, NtTPC1A and NtTPC1B, that are homologous to TPC1 (two pore channel) from suspension-cultured tobacco BY-2 cells. NtTPC1s complemented the growth of a Saccharomyces cerevisiae mutant defective in CCH1, a putative Ca 2+ channel, in a low Ca 2+ medium, suggesting that both products permeate Ca 2+ through the plasma membrane. Cosuppression of NtTPC1s in apoaequorin-expressing BY-2 cells resulted in inhibition of rise in cytosolic free Ca 2+ concentration ([Ca 2+] cyt) in response to sucrose and a fungal elicitor cryptogein, while it did not affect hypoosmotic shock-induced [Ca 2+] cyt increase. Cosuppression of NtTPC1s also caused suppression of cryptogein-induced programmed cell death and defense-related gene expression. These results suggest that NtTPC1s are involved in Ca 2+ mobilization induced by the cryptogein and sucrose, and have crucial roles in cryptogein-induced signal transduction pathway.
Published Version
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