Influx of extracellular Ca2+ involved in jasmonic-acid-induced elevation of [Ca2+]cyt and JR1 expression in Arabidopsis thaliana

The changes in cytosolic Ca2+ levels play important roles in the signal transduction pathways of many environmental and developmental stimuli in plants and animals. We demonstrated that the increase in cytosolic free Ca2+ concentration ([Ca2+](cyt)) of Arabidopsis thaliana leaf cells was induced by exogenous application of jasmonic acid (JA). The elevation of [Ca2+](cyt) was detected within 1 min after JA treatment by the fluorescence intensity using laser scanning confocal microscopy, and the elevated level of fluorescence was maintained during measuring time. With pretreatment of nifedipine (Nif), a nonpermeable L-type channel blocker, the fluorescence of [Ca2+](cyt) induced by JA was inhibited in a dose-dependent manner. In contrast, verapamil, another L-type channel blocker, had no significant effect. Furthermore, Nif repressed JA-induced gene expression of JR1 but verapamil did not. JA-induced gene expression could be mimicked by higher concentration of extracellular Ca2+. W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide], an antagonist of calmodulin (CaM), blocked the JA induction of JR1 expression while W-5 [N-(6-aminohexyl)-1-naphthalenesulfonamide], its inactive antagonist, had no apparent effect. These data provide the evidence that the influx of extracellular Ca2+ through Nif sensitive plasma membrane Ca2+ channel may be responsible for JA-induced elevation of [Ca2+](cyt) and downstream gene expression, CaM may be also involved in JA signaling pathway.