Primary carbon partitioning in red algae and green plants

虽然碳的主要途径在光合作用生物中非常保守，但碳退出卡尔文循环的方式存在显著变化，特别是当考虑到所有光合作用生物时，而不仅仅是植物。大多数陆生真核光合生物属于绿枝植物，其特点是：(1)叶绿体由两个包膜包围，(2)利用叶绿素a和b，(3)在叶绿体基质中储存淀粉，(4)在细胞质中合成蔗糖。在陆地植物和绿藻中，Calvin-Benson循环的产物，磷酸三糖GAP和磷酸三糖DAP从叶绿体输出到细胞质是由磷酸三糖/磷酸反转运蛋白[1]介导的。编码这类转运体的同源基因也可以在红藻的基因组和Chromalveolata[2]的成员中发现。然而，只有绿绿植物的成员在塑性淀粉池和胞质蔗糖生物合成之间进行光合作用。我们假设不同的碳分配策略反映在可塑磷酸盐转运子的动力学性质上。这一假设将通过使用红藻中的磷酸盐易位子进行体内和体外实验来验证。

While the primary path of carbon is remarkably conserved in photosynthetic organisms, significant variation exists in the ways that carbon exits the Calvin cycle, especially when all photosynthetic organisms are considered, not just plants. Most terrestrial eukaryotic photosynthetic organisms belong to the Viridiplantae, which are characterized by (1) chloroplasts that are bounded by two envelope membranes, (2) use of chlorophyll a and b, (3) storage of starch inside the chloroplast stroma, and (4) synthesis of sucrose in the cytosol. In land plants and green algae, the export of the products of the Calvin-Benson cycle, triose phosphates GAP and DAP, from chloroplasts to the cytosol is mediated by a triose phosphate/phosphate antiporter [1]. Paralogous genes encoding this class of transporters can also be found in the genomes of the red algae and in members of the Chromalveolata [2]. However, only members of the Viridiplantae partition photoassimilates between a plastidic starch pool and cytosolic sucrose biosynthesis. We hypothesize that different strategies of carbon partitioning are reflected by the kinetic properties of plastidic phosphate translocators. This hypothesis will be tested by in vitro and in vivo experiments using phosphate translocators from red algae.