An Arabidopsis porB porC double mutant lacking light-dependent NADPH:protochlorophyllide oxidoreductases B and C is highly chlorophyll-deficient and developmentally arrested
An Arabidopsis porB porC double mutant lacking light-dependent NADPH:protochlorophyllide oxidoreductases B and C is highly chlorophyll-deficient and developmentally arrested
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DOI：
10.1046/j.1365-313x.2003.01798.x
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发表时间：
2003-07-01
期刊：
影响因子：
7.2
通讯作者：
Armstrong, GA
中科院分区：
文献类型：
--
作者：
Frick, G;Su, QX;Armstrong, GA
在蓝藻通过高等植物生物合成叶绿素（Chls）a和B的关键反应是严格依赖于光的原叶绿素（Pchlide）a到叶绿素（Chlide）a的还原。与其他光合生物不同，被子植物完全依赖这种机制来减少Pchlide，因此需要光变成绿色。在拟南芥中，光依赖性Pchlide还原是由三个结构相关但差异调节的NADPH介导的：Pchlide氧化还原酶，表示为PORA，PORB和PORC。PORA和PORB基因，但不是PORC，在幼苗发育早期强烈表达。相比之下，在较老的幼苗和成年植物中观察到PORB和PORC的表达，而不是PORA。我们已经测试的假设，PORB和PORC管光依赖性叶绿素的生物合成在整个植物发育的大部分，通过确定的拟南芥，第一个高等植物POR突变体的特征porB和porC突变体。porB-1和porC-1突变体缺乏各自的POR转录本和特异性POR同种型，因为玉米解离（Ds）转座因子的衍生物中断了相应的基因。单por突变体，光周期生长，显示在整个植物或叶绿体超微结构水平上没有明显的表型，虽然porB-1突变体具有较低的广泛的叶绿体内膜。然而，一个光生长的porB-1 porC-1双突变体开发的幼苗致死xantha表型在子叶阶段，只含有少量的叶绿素a，并拥有叶绿体，主要是未堆叠的类囊体膜。因此，PORB和PORC似乎在维持绿色植物中光依赖的叶绿素生物合成中起着多余的作用，并且一起对生长和发育至关重要。
A key reaction in the biosynthesis of chlorophylls (Chls) a and b from cyanobacteria through higher plants is the strictly light-dependent reduction of protochlorophyllide (Pchlide) a to chlorophyllide (Chlide) a. Angiosperms, unlike other photosynthetic organisms, rely exclusively upon this mechanism to reduce Pchlide and hence require light to green. In Arabidopsis, light-dependent Pchlide reduction is mediated by three structurally related but differentially regulated NADPH:Pchlide oxidoreductases, denoted as PORA, PORB, and PORC. The PORA and PORB genes, but not PORC, are strongly expressed early in seedling development. In contrast, expression of PORB and PORC, but not PORA, is observed in older seedlings and adult plants. We have tested the hypothesis that PORB and PORC govern light-dependent Chl biosynthesis throughout most of the plant development by identifying porB and porC mutants of Arabidopsis, the first higher plant por mutants characterized. The porB-1 and porC-1 mutants lack the respective POR transcripts and specific POR isoforms because of the interruption of the corresponding genes by a derivative of the maize Dissociation (Ds ) transposable element. Single por mutants, grown photoperiodically, display no obvious phenotypes at the whole plant or chloroplast ultrastructural levels, although the porB-1 mutant has less extensive etioplast inner membranes. However, a light-grown porB-1 porC-1 double mutant develops a seedling-lethal xantha phenotype at the cotyledon stage, contains only small amounts of Chl a, and possesses chloroplasts with mostly unstacked thylakoid membranes. PORB and PORC thus seem to play redundant roles in maintaining light-dependent Chl biosynthesis in green plants, and are together essential for growth and development.