Department of Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg (JMU), Würzburg, D-97082, Germany.
IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, Montpellier, 34060, France.
New Phytol. 2023 Sep;239(6):2225-2234. doi: 10.1111/nph.19124. Epub 2023 Jul 11.
Plant transpiration is controlled by stomata, with S- and R-type anion channels playing key roles in guard cell action. Arabidopsis mutants lacking the ALMT12/QUAC1 R-type anion channel function in guard cells show only a partial reduction in R-type channel currents. The molecular nature of these remaining R-type anion currents is still unclear. To further elucidate this, patch clamp, transcript and gas-exchange measurements were performed with wild-type (WT) and different almt mutant plants. The R-type current fraction in the almt12 mutant exhibited the same voltage dependence, susceptibility to ATP block and lacked a chloride permeability as the WT. Therefore, we asked whether the R-type anion currents in the ALMT12/QUAC1-free mutant are caused by additional ALMT isoforms. In WT guard cells, ALMT12, ALMT13 and ALMT14 transcripts were detected, whereas only ALMT13 was found expressed in the almt12 mutant. Substantial R-type anion currents still remained active in the almt12/13 and almt12/14 double mutants as well as the almt12/13/14 triple mutant. In good agreement, CO -triggered stomatal closure required the activity of ALMT12 but not ALMT13 or ALMT14. The results suggest that, with the exception of ALMT12, channel species other than ALMTs carry the guard cell R-type anion currents.
植物蒸腾作用受气孔控制，S-型和 R-型阴离子通道在保卫细胞活动中起关键作用。拟南芥突变体缺乏 ALMT12/QUAC1 R-型阴离子通道在保卫细胞中的功能，仅显示 R-型通道电流的部分减少。这些剩余的 R-型阴离子电流的分子性质仍不清楚。为了进一步阐明这一点，使用野生型（WT）和不同 almt 突变体植物进行了膜片钳、转录和气体交换测量。almt12 突变体中 R-型电流部分表现出相同的电压依赖性、对 ATP 阻断的敏感性，并且缺乏氯离子通透性，与 WT 相同。因此，我们询问了 ALMT12/QUAC1 缺失突变体中 R-型阴离子电流是否是由其他 ALMT 同工型引起的。在 WT 保卫细胞中检测到 ALMT12、ALMT13 和 ALMT14 转录本，而在 almt12 突变体中仅发现 ALMT13 表达。在 almt12/13 和 almt12/14 双突变体以及 almt12/13/14 三突变体中，仍有大量的 R-型阴离子电流保持活跃。与预期一致，CO 触发的气孔关闭需要 ALMT12 的活性，但不需要 ALMT13 或 ALMT14 的活性。结果表明，除了 ALMT12 之外，其他通道种类而不是 ALMTs 携带保卫细胞 R-型阴离子电流。
