Cellular and molecular mechanisms underlying single-cell C4 photosynthesis in Chenopodiaceae species

植物和藻类等光合生物进行最重要的生物过程，即光合作用，将大气中的二氧化碳转化为所有生命形式生长和发育所必需的有机产品。在陆地植物中，已确定三种光合作用模式：C3、C4 和景天酸代谢 (CAM)，其中 C4 和 CAM 植物在 CO2 限制条件下效率最高。四十多年来，人们广泛认为 C4 光合作用需要两种称为 Kranz 解剖学的细胞类型相互作用，每种细胞都具有不同的叶绿体超微结构和生物化学。最近，藜科的四个成员在单个细胞内执行 C4 光合作用途径的发现对克兰兹范式提出了挑战。这些藜足类物种通过将主要细胞器和关键光合酶划分为两个独立的细胞内细胞质子区室，实现了在单细胞中进行 C4 光合作用的新方法。因此，这些独特的物种提供了理想的模型系统，用于检查控制单个植物细胞中复杂结构和功能极性发展的调节因素。 ******我的研究计划的长期目标是阐明负责单细胞 C4 光合作用的发育和功能的细胞和分子机制。这将通过结合生物化学、生物信息学、细胞、分子遗传学和生理学技术的各种方法来解决。我们有证据表明这些光合基因的表达在转录后水平受到调节，并开发了分子工具来表征这些机制。因此，我的短期目标是：（1）表征在单细胞 C4 系统建立过程中调节光合基因表达的分子过程（2）表征负责将蛋白质选择性导入二态性叶绿体的蛋白质导入途径，使 C4 途径在单细胞中发挥作用，（3）检查细胞骨架及其相互作用蛋白质在细胞器运动中的作用，从而导致单细胞 C4 系统中细胞极性的建立，以及凸轮系统。了解这种复杂而有趣的光合作用途径的分子基础将有助于了解这些植物如何在高温和水分胁迫的条件下茁壮成长，这会严重影响更常见和不太专业的 C3 植物的光合作用生产力。在当前全球不稳定的天气模式下，这一点可能很重要，因为气温升高导致二氧化碳供应量减少和水分压力增加，这将为具有 C4 特征的植物提供优势。

Plants and photosynthetic organisms such as algae perform the most important biological process known as photosynthesis that converts atmospheric CO2 into organic products essential for growth and development of all forms of life. In terrestrial plants, three modes of photosynthesis, C3, C4 and Crassulacean acid metabolism (CAM), have been identified with C4 and CAM plants being the most efficient under CO2 limiting conditions. For more than forty years, it has been widely accepted that the C4 photosynthesis requires the interaction of two cell types known as Kranz anatomy, each has distinct chloroplast ultrastructure and biochemistry. This Kranz paradigm was recently challenged with findings that four members of family Chenopodiaceae perform C4 photosynthetic pathway within individual cells. These chenopod species achieve novel means for performing the C4 photosynthesis in a single cell by partitioning of major organelles and key photosynthetic enzymes into two separate intracellular cytoplasmic subcompartments. Thus, these unique species provide ideal model systems with which to examine the regulatory factors controlling the development of complex structural and functional polarity in a single plant cell. ******The long-term goal of my research program is to elucidate the cellular and molecular mechanisms responsible for the development and function of single-cell C4 photosynthesis. This will be addressed through various approaches that combine biochemical, bioinformatics, cellular, molecular genetics, and physiological techniques. We have evidence that the expression of these photosynthetic genes is regulated at a posttranscriptional level and have developed molecular tools to characterize these mechanisms. Thus, my short-term objectives are to: (1) characterize the molecular processes that regulate the expression of photosynthetic genes during the establishment of the single-cell C4 system (2) characterize the protein import pathway responsible for the selective import of proteins into the dimorphic chloroplasts allowing the C4 pathway to function in a single cell, (3) examine the role of the cytoskeleton and its interacting proteins involved in the movement of organelles leading to the establishment of cellular polarity in the single-cell C4 systems and CAM systems. Understanding the molecular basis of this complex and interesting photosynthetic pathway will provide insights into how these plants thrive under conditions of high temperature and water stress which can severely affect photosynthetic productivity in the more common and less specialized C3 plants. This could be important under the current global unstable weather patterns, where reduced CO2 availability and increased water stress caused by higher temperatures would offer an advantage to plants with C4 features.