Engineering the GORK K+ channel to enhance stomatal kinetics

气孔是开闭以平衡CO2进入叶片进行光合作用的需要与通过蒸腾减少水分损失和防止叶片干燥的需要的孔。气孔是未来20-30年水资源和作物生产危机的核心：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，预计在20-30年之前将再次翻一番。2010-12年和2018年的干旱仅英国农民就损失了约12亿英镑，在过去五年中，全球每年的损失估计为数千亿英镑。因此，气孔是努力提高作物性能的重要目标，特别是在全球气候变化的情况下。气孔开闭是由气孔周围保卫细胞的溶质和水分运输所驱动的。我们对这些过程的深入了解使保卫细胞成为最著名的植物细胞模型之一，并为工程气孔改善作物水分利用的前景提供了真实的物质。在自然环境中，光线会发生波动，例如云层经过时。大多数植物的气孔对光照的反应是通过打开气孔来增加光合作用的CO2进入，当光照强度下降和光合作用对CO2的需求下降时，气孔孔径会减小。光合作用通常跟踪光的波动，但气孔的反应要慢得多。当光强升高时，气孔反应较慢，限制气体交换，减少光合作用对碳的同化;当光强迅速下降时，气孔反应较慢，导致蒸腾作用，而没有相应的同化作用。我们和其他人已经推断，如果气孔运动的速率能够更好地与光合需求的变化相匹配，那么同化作用，从而作物产量，可以在植物用水减少的同时得到增强。最近，我们发现，通过引入合成的光激活K+通道，BLINK 1，足以在模式植物拟南芥中增加生物量并将相关的用水量减少2倍。此外，我们已经证明，类似的收益是可能的，通过改变的K+通道，自然发生在气孔和其他植物细胞的活性的内在控制。这些研究结果表明，加速气孔作为一种策略，以提高作物收益，同时保持水和第二个战略的基础上的属性的通道原生的气孔。我们在这里提出了一个相互关联的努力，结合我们的知识，本地K+通道调节和光遗传学在两个不同的，但相关的战略。我们将设计天然K+通道，以提高水利用效率和生物量产量，我们将联合收割机将我们对这些通道的了解与光遗传学相结合，使通道调节受到光的直接控制。作为一个原理证明，我们将使用拟南芥作为一个模型，在许多作物中具有直系同源物的K+通道。此外，我们希望开发和验证一套新的光遗传学工具和策略，这些工具和策略基于对已知光遗传学光开关相互作用的修饰，这些光遗传学光开关将广泛适用于植物。这些目标与我们开发生物工程的光遗传学方法的长期利益相吻合，这些方法整合了植物的原生过程。

Stomata are pores that open and close to balance the requirement for CO2 entry to the leaf for photosynthesis against the need to reduce water loss via transpiration and prevent leaf drying. Stomata are 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 droughts of 2010-12 and 2018 cost UK farmers alone an estimated £1.2B and worldwide costs year-by-year are estimated in the hundreds of billions of pounds over the past five years. Thus stomata are an important target in efforts to improve crop performance, especially in the face of global climate change. Stomatal opening and closing are driven by solute and water transport of the guard cells which surround the stomatal pore. Our deep knowledge of these processes has made the guard cell one of the best-known plant cell models and gives real substance to prospects for engineering stomata to improve water use by crops.In the natural environment light fluctuates, for example as clouds pass over. The stomata of most plants respond to light by opening the stomatal pore to increase CO2 access for photosynthesis, and they reduce the pore aperture when the light intensity drops and the demand for CO2 by photosynthesis declines. Photosynthesis generally tracks light fluctuations, but stomata are much slower to respond. The slower response of stomata can limit gas exchange and reduce carbon assimilation by photosynthesis when light intensity rises and lead to transpiration without corresponding assimilation when light intensity drops quickly. We and others have reasoned that assimilation, and consequently crop yields, could be enhanced concurrent with an decrease in water use by plants if the rates of stomatal movements could be better matched to variations in photosynthetic demand.Recently, we found that accelerating ion flux in stomatal guard cells by introducing a synthetic, light-activated K+ channel, BLINK1, was sufficient to increase the biomass and reduce the associated water use by 2-fold in the model plant Arabidopsis. Furthermore, we have demonstrated that analogous gains are possible by altering the intrinsic controls on the activity of a K+ channel that occurs naturally in stomata and other plant cells. These findings demonstrate the potential of accelerating stomata as a strategy to enhance crop gains while conserving water and a second strategy based on the properties of a channel native to stomata.We propose here an interlinked effort, combining our knowledge of native K+ channel regulation and of optogenetics in two distinct but related strategies. We will engineer native K+ channels for gains in water use efficiency and biomass yield and we will combine our knowledge of these channels with optogenetics to bring channel regulation under direct control by light. As a proof-of-principle, we will use Arabidopsis as a model that harbours K+ channels with orthologues in many crops. Additionally, we expect to develop and validate a new set of optogenetic tools and strategies based around modifications to the interactions of a known optogenetic photoswitch that will be widely applicable in plants. These aims dovetail with our longer-term interests in developing optogenetic approaches to bioengineering that integrate within processes native to the plant.