Baetz Ulrike, Eisenach Cornelia, Tohge Takayuki, Martinoia Enrico, De Angeli Alexis
Department of Plant and Microbial Biology, University of Zurich, 8008 Zurich, Switzerland (U.B., C.E., E.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (T.T.); and Institut de Biologie Intégrative de la Cellule, CNRS, 91190 Gif-Sur-Yvette, France (A.D.A.).
Department of Plant and Microbial Biology, University of Zurich, 8008 Zurich, Switzerland (U.B., C.E., E.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (T.T.); and Institut de Biologie Intégrative de la Cellule, CNRS, 91190 Gif-Sur-Yvette, France (A.D.A.)
Plant Physiol. 2016 Oct;172(2):1167-1181. doi: 10.1104/pp.16.00183. Epub 2016 Aug 8.
The ability to control the cytoplasmic environment is a prerequisite for plants to cope with changing environmental conditions. During salt stress, for instance, Na and Cl are sequestered into the vacuole to help maintain cytosolic ion homeostasis and avoid cellular damage. It has been observed that vacuolar ion uptake is tied to fluxes across the plasma membrane. The coordination of both transport processes and relative contribution to plant adaptation, however, is still poorly understood. To investigate the link between vacuolar anion uptake and whole-plant ion distribution during salinity, we used mutants of the only vacuolar Cl channel described to date: the Arabidopsis (Arabidopsis thaliana) ALMT9. After 24-h NaCl treatment, almt9 knock-out mutants had reduced shoot accumulation of both Cl and Na In contrast, almt9 plants complemented with a mutant variant of ALMT9 that exhibits enhanced channel activity showed higher Cl and Na accumulation. The altered shoot ion contents were not based on differences in transpiration, pointing to a vacuolar function in regulating xylem loading during salinity. In line with this finding, GUS staining demonstrated that ALMT9 is highly expressed in the vasculature of shoots and roots. RNA-seq analysis of almt9 mutants under salinity revealed specific expression profiles of transporters involved in long-distance ion translocation. Taken together, our study uncovers that the capacity of vacuolar Cl loading in vascular cells plays a crucial role in controlling whole-plant ion movement rapidly after onset of salinity.
控制细胞质环境的能力是植物应对不断变化的环境条件的先决条件。例如，在盐胁迫期间，钠和氯被隔离到液泡中，以帮助维持细胞质离子稳态并避免细胞损伤。据观察，液泡离子吸收与跨质膜的通量相关。然而，这两个运输过程的协调以及对植物适应性的相对贡献仍知之甚少。为了研究盐胁迫期间液泡阴离子吸收与全株离子分布之间的联系，我们使用了迄今为止描述的唯一液泡氯通道的突变体：拟南芥ALMT9。经过24小时的氯化钠处理后，almt9基因敲除突变体地上部的氯和钠积累量减少。相比之下，用表现出增强通道活性的ALMT9突变变体互补的almt9植株显示出更高的氯和钠积累量。地上部离子含量的改变并非基于蒸腾作用的差异，这表明液泡在盐胁迫期间调节木质部装载中具有功能。与此发现一致，GUS染色表明ALMT9在地上部和根部的维管系统中高度表达。对盐胁迫下almt9突变体的RNA测序分析揭示了参与长距离离子转运的转运蛋白的特定表达谱。综上所述，我们的研究发现，维管细胞中液泡氯装载能力在盐胁迫开始后迅速控制全株离子移动中起着关键作用。
