植物碳酸酐酶及其互作蛋白在保卫细胞CO2信号传导途径中的作用和分子机制

Elevated CO2 is an important signal that mediates stomatal closing. The continuing rise in atmospheric CO2 has been shown to reduce stomatal apertures in many plant species and this in turn will increasingly affect carbon fixation, plant water use efficiency and leaf heat stress in plants on a global scale. However, the mechanisms that mediate early CO2 reception and CO2 signaling and control global carbon fixation and water use efficiency of plants have remained completely unknown. Our previous study showed that carbonic anhydrases CA1 and CA4 play key roles in early stomatal CO2 singaling, not only regualte CO2-induced stomatal movement, but also regulate stomatal development. Futher research showed that carbonic anhydrases catalysis is the main mechanism and HCO3- is the main signal to induce stomatal closing (Hu et al, 2010, Nature Cell Biology; Xue et al, 2011, EMBO J). However, the detailed process and mechanism that how CA1 and CA4 regulate CO2-induced stomatal movement and stomatal development remain obscure. The proposed project here is to investigate CA1 and CA4 -interacting proteins and achieve the molecular mechanisms that mediate CO2 signal tranduction in guard cells via these proteins.Specific research aims are proposed：1)Determine where is the original CO2 signal from? 2) Investigate how CA1 and CA4-mediated CO2 transduce in different cell orannelles. 3) Identification of CA1 and CA4-interacting proteins and their roles in CO2-induced stomatal signaling pathway.4)Investigate CO2-controlled stomatal development mechanisms mediated by CA1 and CA4.5)Investigate the physiological mechanism that CA1 and CA4 improve water use efficiency and their possible applications in genetic agricultural improvement.This project is of major relevance for carbon fixation and water use efficiency of plants in light of the continuing atmospheric CO2 increase and focused on CO2 signaling in plant guard cells.

大气中CO2浓度逐渐升高，减小植物气孔开度，进而影响植物的气体交换和导致植物的高温胁迫。但是保卫细胞中CO2如何传导和调控气体交换的过程和机制尚不清楚。在前期工作中我们鉴定出CA1和CA4在CO2信号传导途径中起关键作用，不仅调控气孔运动，还调控气孔发育(发表于Nature Cell Biology, 2010和EMBO J, 2011)，但是CA1/CA4在CO2信号传导中的具体过程和机制还不清楚。本项目旨在研究CA1/CA4及其互作蛋白在CO2信号传导中的具体分子机制。主要内容包括：1) 研究CA1/CA4 介导的CO2调控气孔运动的细胞来源。2) 研究CA1/CA4介导的CO2信号如何在细胞器传导。3) 重点鉴定CA1/CA4的互作蛋白及其功能。4) 研究CA1/CA4介导的CO2调控气孔发育的分子机制。5) 研究CA1/CA4提高水分利用率的生理基础和它们在抗逆改良的应用途径。

大气环境中CO2浓度逐渐升高，严重影响植物的生长发育，不仅减小植物气孔开度，还减少气孔发育，进而影响植物的气体交换和高温胁迫。前期工作中我们鉴定出CA1和CA4在CO2信号传导途径中起关键作用，不仅调控气孔运动，还调控气孔发育。但是CA1/CA4在CO2信号传导中的具体过程和机制还不清楚。本项目研究发现：1）CA1/CA4介导CO2诱导的气孔关闭信号主要来源于保卫细胞，但也不排除叶肉细胞的调控作用。2）解析了CA4在细胞膜表达和CA1在叶绿体表达都是能够快速介导CO2诱导的气孔关闭，构建的数学模型阐明了碳酸酐酶引起的HCO3-动态变化量是CO2调控气孔关闭的主要机制。3）阐明了CA4的互作蛋白PIP2A水通道蛋白通过增加CO2通透量来参与CO2调控离子通道的信号传导途径。4）而CA4的另一互作蛋白MPK12主要是通过结合HT1并抑制其活性参与到该途径。 5）在长期高CO2生长下，ca1ca4突变体中气孔密度增加的原因是CRSP和EPF2上升表达，EPF2原肽被CRSP剪切成活性状态，从而增强气孔密度。6）CA1/CA4超量表达能提高拟南芥水分利用率的主要原因是植株具有较低的气孔密度和加强的渗透调节能力。7）将CA1/CA4转化油菜后，也能提高水分利用率，暗示CA1/CA4在抗逆遗传改良中的应用前景。本项目研究更新和进一步完善了保卫细胞CO2信号传导途径的模式，并且提出至少存在2条不同的途径，一条是通过细胞膜，另一条可能来自于叶绿体。为后续研究和进一步解析保卫细胞CO2信号传导的机制提供基础。