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重大变化，特别是当所有光合作用生物都被考虑在内时，而不仅仅是植物。大多数陆地真核生物光合作用生物属于维管藻，其特征是(1)叶绿体被两层被膜包围，(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，三糖磷酸GAP和DAP，从叶绿体输出到细胞质是由磷酸三糖/磷酸逆向转运蛋白介导的[1]。编码这一类转运蛋白的类似基因也可以在红藻的基因组和嗜铬藻的成员中找到[2]。然而，只有病原菌的成员在胞质淀粉池和胞质蔗糖生物合成之间分配光合作用。我们假设，不同的碳分配策略反映在可塑性磷酸盐转运体的动力学性质上。这一假设将通过使用红藻磷酸盐转运体的体外和体内实验来验证。

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.