Molecular Mechanisms of CO2 Signal Transduction in Plants

植物中CO2信号转导的分子机制

• 批准号: 1414339
• 负责人: Julian Schroeder
• 金额: $ 40万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1414339&HistoricalAwards=false
• 关键词: Molecular; Mechanisms; CO2; Signal; Transduction

Plants have many small openings or pores (termed stomata) on the surface of their leaves, by means of which plants control the exchange of gases with the atmosphere. It is through the stomata that plants also lose water vapor; over 95% of plant water loss occurs by transpiration from stomatal pores. Stomatal pores are formed by a pair of guard cells that (by changing shape) control the size of the pore and thereby simultaneously control the rate of water loss from the leaf and the diffusion into the leaf of carbon dioxide from the atmosphere needed for photosynthesis and ultimately growth. There are large changes in the levels of carbon dioxide in the leaves of plants during the day, caused by photosynthesis and respiration. In the longer term, atmospheric carbon dioxide levels are increasing; presently they are 40% higher than before the industrial revolution and are predicted to double during this century. This project will identify and characterize the mechanisms by which plants sense the level of carbon dioxide and use this 1) to regulate the size of the stomatal apertures and 2) to control the number of stomatal pores that form during leaf development. The role of the stomatal pores in simultaneously controlling carbon dioxide exchange and the loss of water from the plant place them in a role central to the response of plants to the continuing increase in atmospheric carbon dioxide and changing patterns of temperature, drought and their associated stresses. However, relatively little is known about the cellular, molecular, genetic and biophysical signaling mechanisms that mediate carbon dioxide control of stomatal function. Identification of the molecular network that controls stomatal aperture and development and understanding physiological function will help predict the effects of rising atmospheric carbon dioxide levels on plants and can contribute to future engineering of crop plants to help avoid heat stress of leaves and enhance their efficiency of water use. In addition to training of graduate students and postdoctoral fellows, the project will provide opportunities for public outreach and research experiences for students from disadvantaged groups underrepresented in science and technology from the Preuss Charter School in San Diego. A network of signal transduction mechanisms sense and transduce changes in carbon dioxide concentrations to regulate both stomatal movements and stomatal development in plants, thereby optimizing carbon dioxide influx, water loss, heat avoidance and plant growth under stress. Achieving a mechanistic molecular biophysical understanding of how the carbon dioxide stimulus is transmitted into the stomatal conductance regulation network is the long-term goal of this research. Robust carbon dioxide signaling mutants have been identified and their mechanisms of action characterized. However, the predicted intracellular bicarbonate sensors remain unknown. Furthermore, recent advances in this project have shown a key role of carbonic anhydrases in the repression of stomatal development by elevated carbon dioxide levels, leading to a model for carbon dioxide input into the stomatal development machinery. This project will investigate new working hypotheses by identifying bicarbonate sensing and signaling mechanisms in guard cells that function in carbon dioxide-induced stomatal closing. Functional multi-component reconstitution of carbon dioxide/bicarbonate signaling using heterologous expression systems will be used to identify the bicarbonate-activated proteins that mediate the carbon dioxide/bicarbonate response. The project will address the function of photosynthesis in guard cells for carbon dioxide control of stomatal movements and the functions of guard/mesophyll cell starch metabolism in carbon dioxide control of stomatal movements. The functions of the newly identified CRSP protease and CRSP homologs identified in a systems level cell wall proteome analysis will be characterized, and a mathematical model and model-driven experiments will be used to identify new mechanisms that function in carbon dioxide regulation of stomatal development. The carbon dioxide regulation of stomatal conductance will also be investigated using a genomic scale new artificial microRNA library recently developed in the laboratory.

植物的叶子表面有许多小开口或气孔（称为气孔），植物通过这些小开口或气孔控制与大气的气体交换。植物也通过气孔失去水蒸气。超过 95% 的植物水分损失是通过气孔蒸腾作用发生的。气孔是由一对保卫细胞形成的，它们（通过改变形状）控制气孔的大小，从而同时控制叶子失水的速度以及光合作用和最终生长所需的大气中二氧化碳扩散到叶子的速度。白天，由于光合作用和呼吸作用，植物叶子中的二氧化碳含量发生很大变化。从长远来看，大气中的二氧化碳含量正在增加；目前，这一数字比工业革命前高出 40%，预计本世纪将翻一番。该项目将确定和表征植物感知二氧化碳水平的机制，并利用该机制 1) 调节气孔孔径的大小，2) 控制叶子发育过程中形成的气孔的数量。气孔在同时控制二氧化碳交换和植物水分流失方面的作用使其在植物对大气二氧化碳持续增加以及温度、干旱及其相关胁迫模式变化的反应中发挥着核心作用。然而，人们对介导二氧化碳控制气孔功能的细胞、分子、遗传和生物物理信号传导机制知之甚少。识别控制气孔孔径和发育的分子网络以及了解生理功能将有助于预测大气二氧化碳水平上升对植物的影响，并有助于未来的作物工程，以帮助避免叶子的热应激并提高其水分利用效率。除了培训研究生和博士后研究员外，该项目还将为圣地亚哥普鲁斯特许学校在科学技术领域代表性不足的弱势群体的学生提供公共宣传和研究经验的机会。信号转导机制网络感知并转导二氧化碳浓度的变化，以调节植物的气孔运动和气孔发育，从而优化二氧化碳流入、水分流失、避热和胁迫下的植物生长。这项研究的长期目标是从分子生物物理学的角度理解二氧化碳刺激如何传递到气孔导度调节网络。已鉴定出强大的二氧化碳信号突变体并表征了其作用机制。然而，预测的细胞内碳酸氢盐传感器仍然未知。此外，该项目的最新进展表明，碳酸酐酶在通过升高二氧化碳水平抑制气​​孔发育中发挥着关键作用，从而建立了二氧化碳输入气孔发育机制的模型。该项目将通过识别在二氧化碳诱导的气孔关闭中起作用的保卫细胞中的碳酸氢盐传感和信号传导机制来研究新的工作假设。使用异源表达系统对二氧化碳/碳酸氢盐信号传导进行功能性多组分重建将用于鉴定介导二氧化碳/碳酸氢盐反应的碳酸氢盐激活蛋白。该项目将研究保卫细胞中光合作用对气孔运动二氧化碳控制的功能以及保卫细胞/叶肉细胞淀粉代谢在二氧化碳控制气孔运动中的功能。将表征系统级细胞壁蛋白质组分析中新鉴定的 CRSP 蛋白酶和 CRSP 同源物的功能，并将使用数学模型和模型驱动的实验来确定在气孔发育的二氧化碳调节中发挥作用的新机制。还将使用实验室最近开发的基因组规模的新型人工 microRNA 文库来研究二氧化碳对气孔导度的调节。