Function and stimulation of the transient increase of the leaf apoplastic pH during exposure to chlorine-stress

暴露于氯胁迫期间叶片质外体 pH 值短暂增加的功能和刺激

• 批准号: 405854264
• 负责人: Professor Dr. Christoph-Martin Geilfus
• 金额: --
• 依托单位: Institut für Bodenkunde und Pflanzenernährung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/405854264?language=en
• 关键词: Function; stimulation; transient; increase; leaf

The apoplast is an extracellular compartment that lies outside the plasma membrane (PM). External stress factors can influence the pH of the fluid film of the leaf apoplast. For instance, the apoplastic pH (pHapo) of field bean (Vicia faba L.) leaves increases minutes after exposing the roots to a stressful dose of NaCl. This increase is transient and lasts over a period of 1-3 hours. It is ascribable to the chloride (Cl−) but not to the sodium or the osmotic component of the NaCl-stress. Although indications increase that this rise of the pHapo could be part of a beneficial response to salt stress, it has received little attention in the previous research. On the one hand, it could be a secondary effect without functional implication, arising i.e. from Cl− movements across the PM. On the other hand, results derived from studies on Vicia faba show that the Cl−-induced transient increase of the leaf pHapo is instrumental for enriching guard cells (GCs) with abscisic acid (ABA). ABA is a phytohormone that controls stomatal aperture. Regarding this enrichment, it is unclear whether the transient increase of the leaf pHapo represents a response to Cl−-stress that alone is sufficient to induce an accumulation of ABA in the GCs. To clarify this, it is planned in the envisaged project to artificially increase the leaf pHapo to increase in a transient way. This is done via the infiltration of a pH buffer. By this means, the effect of the transient pHapo increase on the ABA concentration in the GCs can be investigated in a background in which plants are not Cl−-stressed. This investigation will provide information as to whether the sole presence of the transient Cl−-induced pHapo rise was sufficient to cause the accumulation of ABA in the GCs. If this is not the case, it is likely that the GC ABA enrichment is rather the outcome of an interaction between the Cl− stress-induced pHapo change and other stress responses that arise from Cl−-stress. Ratiometric in planta H+-imaging is used for the non-invasive quantification of the pHapo. Guard cells will be purified from leaves that have shown the transient increase of the pHapo. These GC samples are subjected to different analysis: First, ABA concentration is analyzed via mass spectrometry (MS). Moreover, MS-based shotgun proteomics is applied to investigate pHapo-based effects on abundances of proteins that catalyse the GC-autonomous ABA synthesis or mediate ABA influx into GCs. Furthermore, the project seeks to expand knowledge concerning anionic stimulants other than Cl− that can induce the leaf apoplast to increase pH, when applied at a stressful dose. This could be sulfate, which is a dominant anion in many saline soils. Lastly, the response of the root apoplastic pH to a stressful dose of Cl− is investigated, as our understanding about the regulation of the root pHapo during exposure to Cl−-stress is rudimentary.

质外体是位于质膜（PM）外的细胞外区室。外源胁迫因子可影响叶片质外体液膜的pH值。以蚕豆（Vicia faba L.）叶增加后，暴露的根胁迫剂量的NaCl分钟。这种增加是短暂的，持续1-3小时。它可归因于氯化物（Cl−），而不是钠或NaCl胁迫的渗透组分。虽然有迹象表明pHapo的这种上升可能是对盐胁迫的有益反应的一部分，但在以前的研究中很少受到关注。一方面，它可能是一种没有功能含义的次级效应，即由穿过PM的Cl−运动引起。另一方面，来自蚕豆的研究结果表明，Cl−诱导的叶片pHapo的瞬时增加有助于使保卫细胞（GC）富含脱落酸（阿坝）。阿坝是一种控制气孔开度的植物激素。关于这种富集，目前尚不清楚叶片pHapo的瞬时增加是否代表对Cl−胁迫的响应，仅Cl −胁迫就足以诱导GC中阿坝的积累。为了澄清这一点，在设想的项目中计划人工增加叶片pHapo，以瞬时方式增加。这是通过pH缓冲液的渗透完成的。通过这种方法，可以在植物没有受到Cl−胁迫的背景下研究瞬时pHapo增加对GC中阿坝浓度的影响。这项研究将提供信息，是否单独存在的瞬时Cl-诱导的pHapo上升是足以导致阿坝在GC中的积累。如果不是这种情况，那么GC阿坝富集可能是Cl−胁迫诱导的pHapo变化与Cl−胁迫引起的其他胁迫反应之间相互作用的结果。比率在植物H+成像用于pHapo的非侵入性定量。保卫细胞将从已经显示pHapo瞬时增加的叶子中纯化。对这些GC样品进行不同的分析：首先，通过质谱法（MS）分析阿坝浓度。此外，MS为基础的鸟枪蛋白质组学被应用于研究基于pHapo的蛋白质丰度的影响，催化GC自主阿坝合成或介导阿坝流入GC。此外，该项目旨在扩大有关除Cl−以外的阴离子兴奋剂的知识，这些兴奋剂在施加压力剂量时可以诱导叶质外体增加pH值。这可能是硫酸盐，这是许多盐渍土中的主要阴离子。最后，根质外体pH值的压力剂量的Cl-的反应进行了研究，因为我们的了解的调节过程中暴露于Cl--应力的根pHapo是初步的。