Analysing GORK clustering for enhanced stomatal control

气孔是在植物叶片的不透水角质层上提供气体交换的气孔。它们的打开和关闭是为了平衡光合作用所需的二氧化碳进入与减少水蒸气蒸腾和防止叶子干燥的需要。气孔蒸腾是水资源供应和作物生产危机的核心，预计将在未来20-30年内展开：在全球范围内，农业用水量在过去100年中增加了6倍，是人口增长速度的两倍，预计到2030年将再翻一番。农业中使用的大部分水通过气孔。因此，气孔是调控作物生产性能的重要指标。值得注意的是，面对环境的波动，尤其是光的波动，气孔反应往往会延迟。如果能够提高气孔响应的速度，在不牺牲光合作用中吸收的碳的前提下，提高水分利用效率（=光合作用中固定的碳量/蒸腾的水量）应该是可能的。气孔运动是由溶质运输驱动的——以及随之而来的水的吸收/损失——穿过气孔周围的保护细胞的细胞膜。保卫细胞含有离子通道蛋白，促进气孔运动的阳离子通量。独特的是，一类植物离子通道的打开（或门控）也对外部K+浓度敏感。这些通道存在于烟草、豇豆和拟南芥的保护细胞中，后者仅由GORK基因编码。增加外部K+与K+的平衡电压平行调节通道打开，并影响全细胞电导。这些通道是气孔关闭期间钾离子外排的主要途径，但它们对钾离子的敏感性限制了钾离子的通量，特别是在高外部钾离子条件下。基于最近模型的估计表明，这些通道的通量容量仅适度增加，气孔关闭速度可加快3倍。GORK通道的K+敏感性是通道蛋白本身的特性，这应该有助于操纵K+外泄能力来加速气孔关闭。我的实验室已经发现了证据，证明GORK门控的K+依赖性与它在簇中的组装有关。这些组件需要GORK的所谓“电压传感器域”（VSDs）相互作用。已知vsd的运动将电压与通道门控耦合，因此vsd之间的相互作用可能提供了一种合作自我调节的机制。我现在建议完成GORK - VSD相互作用及其对通道控制和气孔运动的影响的分析。无论其机制如何，很明显，这些发现为探索植物中这类K+通道的独特和基本特性提供了手段，并操纵通道活性，潜在地增强了植物气孔关闭和水分利用的动力学。

Stomata are pores that provide for gaseous exchange across the impermeable cuticle of plant leaves. They open and close to balance the requirement for CO2 entry for photosynthesis against the need to reduce the transpiration of water vapour and prevent leaf drying. Stomatal transpiration is at the centre of a crisis in water availability and crop production that is expected to unfold over the next 20-30 years: globally, agricultural water usage has increased 6-fold in the past 100 years, twice as fast as the human population, and is projected to double again before 2030. The bulk of water used in agriculture passes through the stomatal pore. Thus stomata represent an important target for manipulating crop performance. Significantly, stomatal responses are often delayed in the face of environmental fluctuations, especially of light. Improving water use efficiency (=amount of carbon fixed in photosynthesis/amount of water transpired) should be possible, without a cost to carbon assimilated in photosynthesis, if the speed of stomatal response can be enhanced.Stomatal movements are driven by solute transport - and consequent uptake/loss of water - across the cell membrane of the guard cells which surround the stomatal pore. Guard cells harbour ion channel proteins to facilitate cation flux for stomatal movement. Uniquely, the opening (or gating) of one class of plant ion channels is also sensitive to external K+ concentration. These channels are found in guard cells of tobacco, Vicia and Arabidopsis, in the latter encoded solely by the GORK gene. Increasing K+ outside moderates channel opening in parallel with the equilibrium voltage for K+ and affects whole-cell conductance. These channels are the main pathway for K+ efflux during stomatal closure, but their K+-sensitivity constrains K+ flux capacity, notably at higher external K+. Estimates based on recent modelling suggests that stomatal closure could be accelerated 3-fold with only a moderate increase in the flux capacity of these channels.The K+-sensitivity of the GORK channel is a property of the channel protein itself, which should facilitate manipulating K+ efflux capacity to accelerate stomatal closure. My laboratory has uncovered evidence that the K+-dependence of GORK gating is associated with its assembly in clusters. These assemblies require the the so-called 'voltage-sensor domains' (VSDs) of GORK to interact with one another. Movement of the VSDs is known to couple voltage to channel gating, so it is likely that interaction between VSDs provides a mechanism for cooperative self-regulation. I propose now to complete the analysis of GORK VSD interaction and the consequences for channel control and for stomatal movements. Regardless of the mechanism, it is clear that these discoveries offer the means to explore a unique and fundamental property of this class of K+ channels in plants and to manipulate channel activity, potentially enhancing the kinetics of stomatal closure and water use by the plant.