Data_Sheet_3_Identification of Genes Preferentially Expressed in Stomatal Guard Cells of Arabidopsis thaliana and Involvement of the Aluminum-Activated Malate Transporter 6 Vacuolar Malate Channel in Stomatal Opening.pdf

Stomatal guard cells (GCs) are highly specialized cells that respond to various stimuli, such as blue light (BL) and abscisic acid, for the regulation of stomatal aperture. Many signaling components that are involved in the stomatal movement are preferentially expressed in GCs. In this study, we identified four new such genes in addition to an aluminum-activated malate transporter, ALMT6, and GDSL lipase, Occlusion of Stomatal Pore 1 (OSP1), based on the expression analysis using public resources, reverse transcription PCR, and promoter-driven β-glucuronidase assays. Some null mutants of GC-specific genes evidenced altered stomatal movement. We further investigated the role played by ALMT6, a vacuolar malate channel, in stomatal opening. Epidermal strips from an ALMT6-null mutant exhibited defective stomatal opening induced by BL and fusicoccin, a strong plasma membrane H+-ATPase activator. The deficiency was enhanced when the assay buffer [Cl–] was low, suggesting that malate and/or Cl– facilitate efficient opening. The results indicate that the GC-specific genes are frequently involved in stomatal movement. Further detailed analyses of the hitherto uncharacterized GC-specific genes will provide new insights into stomatal regulation.

气孔保卫细胞（Stomatal guard cells, GCs）是一类高度特化的细胞，可响应蓝光（blue light, BL）、脱落酸（abscisic acid）等多种刺激，以调控气孔开度。诸多参与气孔运动的信号组分在保卫细胞中优先表达。本研究依托公共数据库资源、逆转录PCR（reverse transcription PCR）及启动子驱动的β-葡萄糖醛酸苷酶（β-glucuronidase）检测实验，在铝激活苹果酸转运蛋白（aluminum-activated malate transporter, ALMT6）与GDSL脂肪酶类气孔阻塞蛋白1（Occlusion of Stomatal Pore 1, OSP1）之外，鉴定出4个此类新基因。部分保卫细胞特异性基因的无效突变体表现出气孔运动异常。本研究进一步探究了液泡苹果酸通道ALMT6在气孔开放中的调控作用：ALMT6无效突变体的表皮条带在蓝光与强质膜H+-ATP酶激活剂壳梭孢素（fusicoccin）诱导的气孔开放过程中存在缺陷；当实验缓冲液的氯离子浓度较低时，该缺陷会进一步加剧，提示苹果酸及/或氯离子可促进气孔高效开放。上述结果表明，保卫细胞特异性基因频繁参与气孔运动调控；对迄今尚未被解析的保卫细胞特异性基因开展更细致的分析，将为气孔调控机制研究提供新视角。