Malcheska Frosina, Ahmad Altaf, Batool Sundas, Müller Heike M, Ludwig-Müller Jutta, Kreuzwieser Jürgen, Randewig Dörte, Hänsch Robert, Mendel Ralf R, Hell Rüdiger, Wirtz Markus, Geiger Dietmar, Ache Peter, Hedrich Rainer, Herschbach Cornelia, Rennenberg Heinz
Professur für Baumphysiologie, Institut für Forstwissenschaften, Albert-Ludwigs-Universität Freiburg, 79110 Freiburg, Germany (F.M., J.K., D.R., C.H., H.R.).
Department of Botany, Faculty of Life Sciences, Aligrah Muslim University, Aligrah 202002, India (A.A.).
Plant Physiol. 2017 Jun;174(2):798-814. doi: 10.1104/pp.16.01784. Epub 2017 Apr 26.
Water limitation of plants causes stomatal closure to prevent water loss by transpiration. For this purpose, progressing soil water deficit is communicated from roots to shoots. Abscisic acid (ABA) is the key signal in stress-induced stomatal closure, but ABA as an early xylem-delivered signal is still a matter of debate. In this study, poplar plants () were exposed to water stress to investigate xylem sap sulfate and ABA, stomatal conductance, and sulfate transporter () expression. In addition, stomatal behavior and expression of ABA receptors, drought-responsive genes, transcription factors, and were studied after feeding sulfate and ABA to detached poplar leaves and epidermal peels of Arabidopsis (). The results show that increased xylem sap sulfate is achieved upon drought by reduced xylem unloading by PtaSULTR3;3a and PtaSULTR1;1, and by enhanced loading from parenchyma cells into the xylem via PtaALMT3b. Sulfate application caused stomatal closure in excised leaves and peeled epidermis. In the loss of sulfate-channel function mutant, At, sulfate-triggered stomatal closure was impaired. The QUAC1/ALMT12 anion channel heterologous expressed in oocytes was gated open by extracellular sulfate. Sulfate up-regulated the expression of , a key step of ABA synthesis, in guard cells. In conclusion, xylem-derived sulfate seems to be a chemical signal of drought that induces stomatal closure via QUAC1/ALMT12 and/or guard cell ABA synthesis.
植物的水分限制会导致气孔关闭，以防止通过蒸腾作用失水。为此，土壤水分亏缺的加剧会从根部传递到地上部分。脱落酸（ABA）是胁迫诱导气孔关闭的关键信号，但ABA作为早期通过木质部传递的信号仍存在争议。在本研究中，将杨树植株（）暴露于水分胁迫下，以研究木质部汁液中的硫酸盐和ABA、气孔导度以及硫酸盐转运蛋白（）的表达。此外，在向杨树离体叶片和拟南芥（）的表皮条饲喂硫酸盐和ABA后，研究了气孔行为以及ABA受体、干旱响应基因、转录因子和的表达。结果表明，干旱时通过PtaSULTR3;3a和PtaSULTR1;1减少木质部卸载，并通过PtaALMT3b增强从薄壁细胞向木质部的装载，从而使木质部汁液中的硫酸盐增加。施用硫酸盐导致离体叶片和去皮表皮中的气孔关闭。在硫酸盐通道功能缺失突变体At中，硫酸盐触发的气孔关闭受到损害。在卵母细胞中异源表达的QUAC1/ALMT12阴离子通道被细胞外硫酸盐门控打开。硫酸盐上调了保卫细胞中ABA合成关键步骤的表达。总之，木质部来源的硫酸盐似乎是干旱的一种化学信号，它通过QUAC1/ALMT12和/或保卫细胞ABA合成诱导气孔关闭。
