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

光合生物进行光合作用，这一过程将二氧化碳转化为所有生命形式都使用的碳水化合物。陆地植物利用C3， C4或天冬酸代谢（CAM）光合途径，C4和CAM在二氧化碳受限的条件下更有效。多年来，人们一直认为所有C4植物都有一种被称为克兰兹解剖的特征，由两种功能和结构不同的光合细胞类型组成。当发现三种陆生植物在单个光合细胞内执行C4途径时，这种克兰兹范式受到了挑战。这些物种通过细胞器和关键酶在两个独立的室中的分配来进行C4光合作用。这些有趣的物种为研究单个植物细胞中复杂结构和生化极性发育的调节因子提供了理想的模型系统。

Photosynthetic organisms perform photosynthesis, a process that converts carbon dioxide into carbohydrates that are used by all life forms. Land plants use C3, C4 or Crassulacean acid metabolic (CAM) photosynthetic pathway with C4 and CAM being more efficient under conditions where CO2 becomes limiting. For many years, it has been accepted that all C4 plants must have a feature called Kranz anatomy consisting of two functionally and structurally distinct photosynthetic cell types. This Kranz paradigm was challenged when three terrestrial plants were found to perform the C4 pathway within individual photosynthetic cells. These species perform C4 photosynthesis by partitioning of organelles and key enzymes in two separate compartments. These interesting species serve as ideal model systems to examine the regulatory factors regulating the development of complex structural and biochemical polarity in a single plant cell. Using B. sinuspersici single-cell C4 species as a model system, the long-term goal of my research program is to continue to identify the regulatory factors that allow C4 photosynthesis to occur within individual cells. My short-term objectives are to: 1) determine the regulatory mechanisms controlling the compartment-specific expression of the C4 pathway genes, particularly the large subunit of Rubisco, 2) determine the molecular factors responsible for the selective import of key photosynthetic enzymes essential to the function of single-cell C4, and 3) identify the cellular components important in the development, function and maintenance of organelle compartmentalization in the single-cell C4 systems as well as the organelle clumping phenomenon observed in the succulent CAM and Kranz-type C4 systems. The proposed research will test the hypotheses that the differentiation of dimorphic chloroplasts requires preferential import of proteins to establish a biochemical gradient, and that the cytoskeleton play a role in the partitioning of organelles essential for the functioning of C4 photosynthesis in a single plant cell.