Masuda Tatsuru, Fusada Naoki, Shiraishi Toshihiko, Kuroda Hirofumi, Awai Koichiro, Shimada Hiroshi, Ohta Hiroyuki, Takamiya Ken-Ichiro
Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan,
Photosynth Res. 2002;74(2):165-72. doi: 10.1023/A:1020951409135.
NADPH-protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide a in the chlorophyll biosynthetic pathway. Here, we identified two distinct POR cDNAs from tobacco. Both POR isoforms are encoded by a respective single copy gene in tobacco genome. The overall deduced amino acid sequences of two tobacco cDNAs, designated here POR1 and POR2, displayed significant identities ( approximately 75%), but showed different patterns of light and developmental regulation. In contrast to the previously isolated POR isoforms of Arabidopsis thaliana and barley, the expression of both tobacco POR isoforms were not negatively regulated by light and persisted in matured green tissues. Furthermore, the expression of both genes appeared to be regulated by a diurnal regulation. These results show a wide variety of light- and development-dependent regulations of POR gene expression among angiosperms. Furthermore, phylogenetic analysis including tobacco revealed that POR gene family is differentially represented by angiosperms, most of which is probably caused by independent gene duplication in individual plant. Present results imply a modification of the previous concept that chlorophyll biosynthesis and chloroplast differentiation in angiosperms are ubiquitously controlled by unique functions of two POR isoforms.
NADPH-原叶绿素酸酯氧化还原酶（POR）在叶绿素生物合成途径中催化光依赖的原叶绿素酸酯a的还原反应。在此，我们从烟草中鉴定出两个不同的POR cDNA。这两种POR同工型均由烟草基因组中各自的单拷贝基因编码。这两个烟草cDNA（在此命名为POR1和POR2）推导的氨基酸序列总体上显示出显著的一致性（约75%），但表现出不同的光调节和发育调节模式。与之前从拟南芥和大麦中分离出的POR同工型不同，两种烟草POR同工型的表达不受光的负调控，并且在成熟绿色组织中持续存在。此外，这两个基因的表达似乎受昼夜节律调节。这些结果表明被子植物中POR基因表达存在多种光依赖和发育依赖的调节。此外，包括烟草在内的系统发育分析表明，POR基因家族在被子植物中的代表情况不同，这很可能是由各个植物中的独立基因复制引起的。目前的结果意味着对之前概念的修正，即被子植物中叶绿素生物合成和叶绿体分化普遍受两种POR同工型独特功能的控制。
