Engineering the GORK K+ channel to enhance stomatal kinetics

气孔是指气孔的打开和关闭，以平衡光合作用所需的二氧化碳进入叶片的需要，以及通过蒸腾减少水分损失和防止叶片干燥的需要。气孔是水资源供应和作物生产危机的中心，预计将在未来20-30年内展开：全球农业用水量在过去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。据估计，2010-12年和2018年的干旱仅给英国农民造成了12亿英镑的损失，而在过去五年里，全球每年的损失估计达到数千亿英镑。因此，气孔是提高作物生产性能的重要目标，特别是在面对全球气候变化的情况下。气孔的开闭是由气孔周围保卫细胞的溶质和水分运输驱动的。我们对这些过程的深入了解使保护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提供了真正的物质前景。在自然环境中，光线是波动的，例如当云层经过时。大多数植物的气孔对光的响应方式是打开气孔以增加光合作用对CO2的获取，当光照强度下降，光合作用对CO2的需求下降时，气孔孔径减小。光合作用通常会跟踪光的波动，但气孔的反应要慢得多。当光强上升时，气孔反应较慢，限制了气体交换，减少了光合作用对碳的吸收；当光强迅速下降时，气孔的蒸腾作用没有相应的同化。我们和其他人认为，如果气孔运动的速率能更好地与光合作用需求的变化相匹配，同化和作物产量就能在减少植物用水的同时得到提高。最近，我们发现通过引入合成的光激活K+通道BLINK1加速气孔保护细胞中的离子通量，足以使模式植物拟南芥的生物量增加2倍，并将相关的水分消耗减少2倍。此外，我们已经证明，通过改变气孔和其他植物细胞中天然存在的K+通道活性的内在控制，也可以获得类似的增益。这些发现证明了加速气孔形成的潜力，作为一种提高作物产量同时节约水分的策略，以及基于气孔固有通道特性的第二种策略。我们在这里提出了一个相互关联的努力，将我们对天然K+通道调节和光遗传学的知识结合在两个不同但相关的策略中。我们将设计原生K+通道，以提高水利用效率和生物量产量，并将这些通道的知识与光遗传学相结合，使通道调节受到光的直接控制。作为原理证明，我们将使用拟南芥作为模型，在许多作物中具有具有同源物的K+通道。此外，我们期望开发和验证一套新的基于修改已知光遗传光开关相互作用的光遗传工具和策略，这将广泛应用于植物。这些目标与我们的长期利益相吻合，即开发光遗传学方法来整合植物原生过程的生物工程。

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.