Developing a synthetic approach to manipulating guard cell membrane transport and stomatal control

气孔是在植物叶片的不渗透角质层上提供气体交换的孔。它们打开和关闭以平衡光合作用对CO2进入的需求，以及减少水蒸气蒸腾和防止叶片干燥的需求。气孔运动是由跨越气孔周围保卫细胞细胞膜的溶质运输以及随之而来的水分吸收/损失驱动的。气孔蒸腾作用是水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，预计在20 - 30年之前将再翻一番。因此，气孔是育种者在操纵作物性能方面的一个重要目标。值得注意的是，气孔反应往往延迟面对环境波动，特别是光。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，如果气孔对光的响应增强，则不需要光合作用中同化的碳的成本。然而，保卫细胞运输及其耦合到气体交换和蒸腾作用的复杂性已经提出了一个强大的障碍，操作，使遗传改良的努力已被普遍证明constrain.Synthetic方法提供了一种方法，生理增强气孔功能。此外，结合定量系统分析，它们提供了一个机会，以获得基本的见解运输的协调在植物细胞系统的稳态。我以前开发的OnGuard软件的定量动态建模的警卫细胞。OnGuard模型明确建立在保卫细胞运输和代谢的分子，生物物理和动力学知识的财富上;它们适应不同植物物种的气孔，迄今为止在实验室研究的全部条件下;并且它们已被证明包含指导细胞和生理水平上的实验所需的真实的预测能力，所述细胞和生理水平的实验从计算机分子操作开始。作为下一个主要步骤，我希望建立定向合成策略的气孔功能的设计，基于气孔保卫细胞的深入了解，并在工作中与光驱动的离子泵和channels.I建议现在使用OnGuard软件建模和探索最有效的方法来提高气孔动力学的发展。与此同时，我的实验室将开发一种合成方法，用所谓的光遗传学工具（光驱动泵和通道）操纵保卫细胞转运，用这些工具来测试和验证模型预测。最重要的是，结合建模和实验的方法将连接的分子组成与气孔的生理特性。他们将加强对保卫细胞运输的理解，并将使水的利用及其与光合碳同化的平衡的新探索成为可能。这些研究将靶向基于OnGuard模型预测的选定光遗传学工具的表达。所获得的知识将有助于完善这些模型，并将允许探索质膜和液泡膜的系列膜之间的动力学和稳态协调。这种协调是已知的气孔开度的控制的基础，但其机制仍然未知。最后，这些研究将有助于确定利用合成方法提高植物水分利用效率的潜力，以减少气孔和光合作用之间动态环境响应的不匹配。

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 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. 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. Thus stomata represent an important target for breeders interested in 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 stomatal response to light are enhanced. However, the complexity of guard cell transport and its coupling to gas exchange and transpiration has presented a formidable barrier to manipulations so that efforts at genetic improvements have generally proven constrained.Synthetic methods offer one approach to physiologically enhancing stomatal function. Furthermore, in combination with quantitative systems analysis they present an opportunity to gain fundamental insights into the coordination of transport in the homeostasis of a plant cell system. I developed previously the OnGuard software for quantitative dynamic modelling of the guard cell. OnGuard models build explicitly on the wealth of molecular, biophysical and kinetic knowledge for guard cell transport and metabolism; they accommodate stomata of different plant species, over the full range of conditions studied in the laboratory to date; and they have been shown to incorporate the real predictive power needed to guide experiments at the cellular and physiological levels that start with molecular manipulations in silico. As the next major step, I wish to establish directed synthetic strategies for design of stomatal function, based on this deep knowledge of stomatal guard cells, and on developments in work with light-driven ion pumps and channels.I propose now to use the OnGuard software to model and explore the most effective approaches to enhancing stomatal kinetics. In parallel, my laboratory will develop a synthetic approach to manipulate guard cell transport with so-called optogenetic tools - light-driven pumps and channels - using these to test and validate the model predictions. Most important, the combined modelling and experimental approaches will connect the molecular components with physiological properties of stomata. They will reinforce an understanding of guard cell transport and will enable novel explorations of water use and its balance with photosynthetic carbon assimilation. These studies will target expression of selected optogenetic tools based on OnGuard model predictions. The knowledge gained will aid in refining these models and will allow exploration of the kinetic and homeostatic coordination between the serial membranes of the plasma membrane and tonoplast. This coordination is known to be fundamental to the control of stomatal aperture, but its mechanism remains unknown. Finally, the studies will serve to establish the potential for improving the efficiency of water use by plants drawing on synthetic methods to reduce the mismatch in dynamic environmental responses between stomata and photosynthesis.