気中汚染物質に対する植物防御の統合的システムに関する分子生理学的研究

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Sulfur dioxide is a toxic gas. Plants has a mechanism to prevent the invasion of sulfur oxide gas into the internal tissue by closing stomata. Stomata is a microscopic opening formed by a pair of guard cells on leaf surface in plants.Some plant growth regulators are also postulated to participate in sulfur dioxide signaling in guard cells by earlier studies, while its rationale was obscure. In this study, we employed quantitative analysis of plant growth regulators, gibberellins, auxin, cytokinines, abscisic acid, jasmonates, and salicylic acid, by liquid chromatography-mass spectrometry. We identified that contents of jasmonates. Therefore, we examined the movement of stomata in a jasmonate-insensitive mutant. Contrary to our expectation, stomata of thejasmonate-insensitive mutant did not show an impairment in sulfur dioxide response, indicating that jasmonate does not participate to sulfur dioxide-induced stomatal closure.Beside above experiment, we have questioned whether cytosolic acidification participates in sulfur dioxide signaling in guard cells or not. We employed an analysis of the mutants, which have stabilized pH of guard cells by mutation in CLCa gene. The mutants of CLCa showed an intensified resistance to sulfur dioxide in terms of stomatal closure induction as well as cell death of guard cells. This supports the idea that cytosolic acidification participates in sulfur dioxide signaling in guard cell leading to stomatal closure. At the same time this provides a potential approach to generate sulfur dioxide-resistant crops.