Yang J, Cheng Q
College of Life Sciences, Peking University, Beijing 100871, China.
Plant Biol (Stuttg). 2004 Sep;6(5):537-44. doi: 10.1055/s-2004-821270.
Light-dependent NADPH-protochlorophyllide oxidoreductase (LPOR) is a nuclear-encoded chloroplast protein in green algae and higher plants which catalyzes the light-dependent reduction of protochlorophyllide to chlorophyllide. Light-dependent chlorophyll biosynthesis occurs in all oxygenic photosynthetic organisms. With the exception of angiosperms, this pathway coexists with a separate light-independent chlorophyll biosynthetic pathway, which is catalyzed by light-independent protochlorophyllide reductase (DPOR) in the dark. In contrast, the light-dependent function of chlorophyll biosynthesis is absent from anoxygenic photosynthetic bacteria. Consequently, the question is whether cyanobacteria are the ancestors of all organisms that conduct light-dependent chlorophyll biosynthesis. If so, how did photosynthetic eukaryotes acquire the homologous genes of LPOR in their nuclear genomes? The large number of complete genome sequences now available allow us to detect the evolutionary history of LPOR genes by conducting a genome-wide sequence comparison and phylogenetic analysis. Here, we show the results of a detailed phylogenetic analysis of LPOR and other functionally related enzymes in the short chain dehydrogenase/reductase (SDR) family. We propose that the LPOR gene originated in the cyanobacterial genome before the divergence of eukaryotic photosynthetic organisms. We postulated that the photosynthetic eukaryotes obtained their LPOR homologues through endosymbiotic gene transfer.
光依赖型NADPH-原叶绿素酸酯氧化还原酶（LPOR）是绿藻和高等植物中一种由核编码的叶绿体蛋白，它催化光依赖型的原叶绿素酸酯还原为叶绿素酸酯的过程。光依赖型叶绿素生物合成发生在所有产氧光合生物中。除被子植物外，该途径与另一条独立的非光依赖型叶绿素生物合成途径共存，后者在黑暗中由非光依赖型原叶绿素酸酯还原酶（DPOR）催化。相比之下，不产氧光合细菌中不存在叶绿素生物合成的光依赖性功能。因此，问题在于蓝细菌是否是所有进行光依赖型叶绿素生物合成的生物的祖先。如果是这样，光合真核生物是如何在其核基因组中获得LPOR同源基因的呢？现在有大量完整的基因组序列可供我们通过进行全基因组序列比较和系统发育分析来检测LPOR基因的进化历史。在此，我们展示了对LPOR和短链脱氢酶/还原酶（SDR）家族中其他功能相关酶进行详细系统发育分析的结果。我们提出LPOR基因起源于真核光合生物分化之前的蓝细菌基因组。我们推测光合真核生物通过内共生基因转移获得了它们的LPOR同源物。
