Roles of AtTPC1, vacuolar two pore channel 1, in Arabidopsis stomatal closure
Islam, M.M., Okayama Univ. (Japan) | Munemasa, S. | Hossain, M.A. | Nakamura, Y. | Mori, I.C. | Murata, Y.
Abscisic acid (ABA) induces production of reactive oxygen species (ROS) and nitric oxide (NO), elevation of the cytosolic free calcium ion concentration ([Casup(2-)]sub(cyt) ) and cytosolic pH (pHsub(cyt)), and activation of S-type anion channels in guard cells, causing stomatal closure. To investigate whether Arabidopsis Two pore channel 1 (AtTPC1) that encodes the slow vacuolar (SV) channel is involved in stomatal closure, we examined stomatal movements and mobilization of second messengers in the attpc 1-2 loss-of-funcrion mutant in response to ABA, methyl jasmonate (MeJA) and Casup(2-). Both ABA and MeJA elicited production of ROS and NO, [Casup(2+)]sub(cyt), oscillations, cytosolic alkalization and activation of S-type anion channel currents to lead to stomatal closure in the attpc 1-2 mutant as well as the wild type. Unlike the wild type, in the attpc 1-2 mutant exogenous Casup(2+) neither induced stomatal closure nor activated plasma membrane S-type anion channel currents despite [Casup(2+)]sub(cyt) elevation. These results indicate that AtTPC1 functions in response to external Casup(2+) but not to ABA and MeJA in Arabidopsis guard cells and suggest that AtTPC1 could be involved in priming of plasma membrane S-type anion channels by external Casup(2+) in Arabidopsis guard cells.
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