A SNARE-Aquaporin complex in stomatal hydraulics

气孔水力学中的 SNARE-水通道蛋白复合物

• 批准号: BB/X013383/1
• 负责人: Michael Blatt
• 金额: $ 88.39万
• 依托单位: University of Glasgow
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FX013383%2F1
• 关键词: SNARE; Aquaporin; complex; stomatal; hydraulics

Stomata are pores that mediate gaseous exchange across the impermeable cuticle of plant leaves. They open for CO2 entry when photosynthesis depletes CO2 inside the leaf, and they close to reduce the transpiration of water vapour and prevent leaf drying when atmospheric humidity is low. Stomata are at the centre of a crisis in water availability and crop production that is beginning to unfold and can only escalate as the global demand, especially in agriculture, outstrips fresh water supplies. Thus stomata are an important target in efforts to enhance crop performance and efficiencies.Stomata of most plants track the immediate demand for CO2 by photosynthesis, responding to CO2 within the leaf, opening in the light and closing in the dark. However, stomatal responses are slow by comparison with that of photosynthesis. Fluctuations in daylight, for example as clouds pass overhead, degrade photosynthesis and reduce water use efficiency (WUE=amount of carbon fixed in photosynthesis/amount of water transpired), principally because stomata generally lag behind changes in light. Synthetic bioengineering has shown substantial gains in photosynthesis and WUE by accelerating the speed of stomatal response. We need now to understand how such gains might be achieved using the processes native to the stomata.Stomatal movement is driven by solute and water transport across the membrane of the guard cells that surround the stomatal pore. Guard cells harbour ion channel proteins to facilitate solute flux and aquaporins to mediate water flux, and they rely on a traffic of membrane vesicles to adjust cell surface area during stomatal movements. Thus, coordination of these three processes is essential for stomatal responses. From our previous work, we know that the dominant ion flux through K+ channels is coupled to membrane traffic by binding between subsets of channels and so-called SNARE proteins that facilitate vesicle traffic and are conserved across land plants. These interactions ensure solute flux and membrane traffic operate in 'lock-step' within guard cells. There is some evidence for a parallel coordination of water flux through aquaporins, but until now we have lacked an understanding of how this coordination might arise.Plasma membrane (PIP) aquaporins are found across all angiosperms. Three PIPs contribute to water flux in guard cells of the model plant Arabidopsis although one, PIP2;1, dominates. We recently uncovered a selective interaction between all three PIPs and the SYP121 protein, one of two principal SNAREs at the plasma membrane. These interactions depend on a cytosolic N-terminal region of SYP121 that is sequence-divergent, but functionally interchangable with other SNAREs and is widely recognised to regulate SNARE activity and vesicle traffic in all eukaryotes. Most exciting, we find that a chimeric SYP121 incorporating the same region of a non-interacting SNARE slows stomatal opening and closing when expressed in guard cells and suppresses WUE and growth when plants experience fluctuating daylight.Our findings are the first direct evidence for SYP121-PIP binding in stomatal movements, and they point to the SNARE subdomain responsible for this action in vivo. SYP121 also binds guard cell K+ channels, coordinating vesicle traffic with K+ flux. Thus, SYP121-PIP binding suggests a SNARE nexus in stomatal regulation; it begs questions about the coordination of PIP and K+ channel binding; and it challenges established dogma about the roles of vesicle traffic in aquaporin hydraulics that impact on WUE and plant biomass gain.We propose now to resolve the binding and function of SYP121 with the guard cell PIPs and to establish the consequences for the plant. This research is to understand the fundamental rules of life. Understanding this SNARE nexus nonetheless carries the promise of a potential target for future bioengineering to accelerate stomatal movements and enhance crop efficiencies.

气孔是在植物叶的不可渗透角质层中介导气体交换的孔。当光合作用耗尽叶子内的二氧化碳时，它们可以进入二氧化碳进入，并且在大气湿度较低时，它们接近减少水蒸气的蒸腾并防止叶片干燥。气孔正处于供水和农作物生产危机的中心，该危机开始展开，并且只能随着全球需求（尤其是在农业的需求）上升级，超越了淡水供应。因此，气孔是提高农作物性能和效率的努力的重要目标。大多数植物的稳定性通过光合作用跟踪对二氧化碳的直接需求，对叶子内的二氧化碳做出了反应，在光线下张开并在黑暗中关闭。但是，与光合作用相比，气孔反应很慢。例如，白天的波动，例如，随着云通过开销，降低光合作用并降低用水效率（Wue =固定在光合作用/转移的水量中的碳量），这主要是因为气孔通常落后于光的变化。合成生物工程已通过加速气孔反应的速度来表现出光合作用和WUE的巨大增长。现在，我们需要了解使用天然气的工艺如何实现此类收益。胸骨运动是由溶质和水在围绕气孔孔的膜的膜上驱动的。警卫细胞携带离子通道蛋白，以促进溶质通量和水通道蛋白介导水通量，它们依靠膜囊泡的流量来调节气孔运动期间的细胞表面积。因此，这三个过程的协调对于气孔反应至关重要。从我们以前的工作中，我们知道，通过K+通道的主要离子通量与膜交通耦合，通过在通道的子集和所谓的SNARE蛋白之间结合，从而促进囊泡流量并在整个土地植物中保守。这些相互作用可确保溶质通量和膜交通在警卫单元内“锁定步骤”中运行。有一些证据表明，水通量通过水通道蛋白平行，但直到现在我们还缺乏对这种配位的理解。铂膜（PIP）在所有被子植物中都发现了水通道蛋白。三个小费在模型植物拟南芥的后卫细胞中有助于水通量，尽管其中一个是pip2; 1占主导地位。我们最近发现了所有三个PIP和SYP121蛋白之间的选择性相互作用，SYP121蛋白是质膜上的两个主要小吃之一。这些相互作用取决于SYP121的胞质N末端区域，该区域是序列发散的，但在功能上可以与其他网罗互换，并且在所有真核生物中都被广泛认可以调节SNARE活动和囊泡流量。最令人兴奋的是，我们发现，嵌合在同一区域中，当植物体验到日光波动时，在警卫单元中表达并抑制Wue和生长时，嵌合了与非交互式圈圈的同一区域，这是气孔的开口和关闭。我们的发现是Syp121 Pip Pip Pip Pip pip the Snare Ection in the Snare seporm procation in the Snare sepor in cootion castion in the Snare caction in cootia cootia cootia con。 SYP121还结合了后卫细胞K+通道，将囊泡流量与K+通量进行协调。因此，SYP121-PIP结合表明在气孔调节中有圈子联系。它引起了有关PIP和K+通道结合的协调的问题；它挑战了对囊泡流量在水通道蛋白液压中的作用，影响对Wue和植物生物量增益的作用。我们现在建议我们解决SYP121与护罩细胞PIPS的结合和功能，并确定对植物的后果。这项研究是了解生活的基本规则。尽管如此，了解这种圈套的纽带仍具有潜在目标的潜在目标，以加速气孔运动并提高作物效率。