Engineering the GORK K+ channel to enhance stomatal kinetics

气孔是打开和关闭的气孔，以平衡二氧化碳进入叶片进行光合作用的需要，以及减少蒸腾失水和防止叶片干燥的需要。气孔处于水资源供应和作物生产危机的中心，这场危机预计将在未来20-30年内展开：全球农业用水量在过去100年里增长了6倍，是人口增长速度的两倍，预计在2030年前将再翻一番。仅2010-12年和2018年的干旱就给英国农民造成了约12亿英镑的损失，在过去五年中，全球每年的成本估计高达数千亿英镑。因此，气孔是努力改善作物表现的一个重要目标，特别是在面对全球气候变化的情况下。气孔的开启和关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卫细胞成为最著名的植物细胞模型之一，并为利用工程气孔来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，光会波动，例如当云层经过时。大多数植物的气孔对光的反应是通过打开气孔来增加光合作用对二氧化碳的获取，当光强下降和光合作用对二氧化碳的需求下降时，它们会减少气孔孔径。光合作用通常跟踪光的波动，但气孔的反应要慢得多。当光强增大时，气孔响应较慢，限制了气体交换，减少了光合作用对碳的同化作用，当光强迅速降低时，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，如果植物的气孔运动速度能够更好地与光合作用需求的变化相匹配，那么植物的同化作用就会增强，从而作物产量也会减少。最近，我们发现，通过引入合成的、光激活的K通道BLINK1来加速气孔保卫细胞中的离子通量，足以在模式植物拟南芥中增加生物量并减少相关用水量2倍。此外，我们已经证明，通过改变自然发生在气孔和其他植物细胞中的K通道活性的内在控制，类似的收益是可能的。这些发现证明了加速气孔作为一种在保持水分的同时提高作物收益的策略的潜力，以及第二种基于气孔固有通道特性的策略。在这里，我们提出了一种相互关联的努力，将我们对天然K通道调节和光遗传学的知识结合在两种不同但相关的策略中。我们将改造天然K通道，以提高水分利用效率和生物量产量，并将我们对这些通道的知识与光遗传学相结合，使通道调节受光的直接控制。作为一个原则证明，我们将使用拟南芥作为一个模型，它在许多作物中含有K通道和同源基因。此外，我们希望开发和验证一套新的光遗传工具和策略，这些工具和策略基于对已知的光遗传光开关相互作用的修改，将在植物中广泛应用。这些目标与我们在开发光遗传生物工程方法方面的长期利益相吻合，这些方法集成在植物本身的过程中。

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.