Molecular Mechanisms of CO2 Signal Transduction in Plants

植物的叶子表面有成千上万个微小的可调节的孔，称为气孔。这些叶片表面的气孔打开和关闭，以调节植物从空气中吸收二氧化碳的必要过程。然而，这些气孔也是植物通过蒸发失去水分的主要途径。一个典型的植物为了生长而吸收（同化）每一个碳原子，就会通过这些气孔损失200到500个水分子。气孔的开启和关闭受包括空气中二氧化碳（CO2）浓度在内的信号调节。与150年前相比，现在空气中的二氧化碳浓度高出50%，而且还在上升，这意味着理论上植物可以更有效地从空气中吸收二氧化碳，同时减少水分的流失。然而，介导这种与农艺学相关的气孔孔径调节的CO2响应的重要机制和基因尚不清楚。该项目将描述新发现的关键基因和蛋白质，并定义细胞网络，通过这些网络，二氧化碳升高控制气孔的关闭，以及低二氧化碳如何控制气孔的打开。该研究可为培育生长性能更好、水分利用效率更高的植物提供必要的知识。操纵气孔对二氧化碳的响应能力对于不利的天气条件、农业地下水枯竭和干旱非常重要，这些在美国和全球的几个主要农业地区变得越来越频繁。科学家们将在圣地亚哥县的普鲁斯公立学校为弱势高中生提供研究实习、专业准备和指导，并与加州大学圣地亚哥分校的ENLACE项目和霍华德大学合作，培训和专业准备访问代表性不足的暑期研究实习生。项目人员将积极参与社区外展工作，使科学和创新接近公众，研究人员将参与最近启动的外展计划，通过与圣地亚哥内城高中中代表性不足的学生进行演讲和讨论。该项目将结合细胞生物学、生物化学、分子遗传学、数学建模、基因组学和系统生物学方法，确定二氧化碳信号网络的新关键分子成分，并表征该网络如何运作以调节气孔孔径。本项目的重点是确定CO2刺激如何传递到气孔运动网络中，其目标是：(1)新发现的基因和编码蛋白介导早期CO2感知和信号转导，将决定生物化学机制和网络原理。(2)结合计算建模、遗传学、代谢组学和分子细胞生物学，探讨叶片细胞间信号传导对气孔运动的影响。(3)定位新分离的叶片温度较低、草气孔对CO2动态响应有缺陷的“寒”突变体，分离出至少一个限速基因的底层基因和蛋白，确定其在草的哑铃状保护细胞的气孔运动中的功能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plant leaves have thousands of microscopic adjustable pores in their leaf surface, called stomata. These stomatal pores in the surface of leaves open and close to regulate the necessary uptake of carbon dioxide into plants from the air. However, these stomatal pores also are the main pathway by which plants lose water, by evaporation. A typical plant loses 200 to 500 water molecules through these stomatal pores for every carbon atom that is absorbed (assimilated) by the plant for growth. The opening and closing of stomata is regulated by signals that include the concentration of carbon dioxide (CO2) in the air. The concentration of CO2 in the air is now 50% higher and rising, compared to only 150 years ago, meaning that plants could theoretically more efficiently take up CO2 from the air, while losing less water. However, important mechanisms and genes that mediate this agronomically relevant CO2 response of stomatal pore aperture regulation remain unknown. This project will characterize newly found key genes and proteins and define cellular networks through which elevated carbon dioxide controls the closing of stomatal pores and how low CO2 controls the opening of stomatal pores. This research can develop the knowledge necessary for the breeding of plants with improved growth properties and enhanced water use efficiency. The ability to manipulate the response of stomatal pores to carbon dioxide is important for unfavorable weather conditions, agricultural ground water depletion and droughts that are becoming more frequent in several of the major agricultural regions in the US as well as globally. The scientists will pursue an outreach program with research internships, professional preparation and mentoring with the public Preuss School for disadvantaged high school students in San Diego County, as well as training and professional preparation of visiting underrepresented summer research interns with UC San Diego's ENLACE program and with Howard University. Project personnel will be active within community outreach work that brings science and innovation close to the public and the investigators will participate in a recently launched outreach program through presentations and discussions with underrepresented students at inner city high schools in San Diego.This project will use a combination of cell biological, biochemical, molecular genetic, mathematical modeling, genomic and systems biological approaches to identify new critical molecular components of the CO2 signaling network and characterize how this network operates to regulate stomatal pore apertures. The focus of this project is to identify how the CO2 stimulus is transmitted into the stomatal movement network, with these goals: (1) Biochemical mechanisms and network principles will be determined by which newly identified genes and the encoded proteins mediate early CO2 sensing and signal transduction. (2) New hypotheses will be investigated on how cell-to-cell signaling in leaves affects CO2 control of stomatal movements by combined computational modeling, genetics, metabolomics and molecular cell biology. (3) Newly isolated "chill" mutants that have cooler leaf temperatures and are defective in the dynamic CO2 response of grass stomata will be mapped and the underlying gene and protein of at least one rate-limiting gene will be isolated and its functions in stomatal movements of the specialized dumbbell-shaped guard cells of grasses will be determined.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.