Franck F, Sperling U, Frick G, Pochert B, van Cleve B, Apel K, Armstrong G A
Laboratory of Photobiology, Department of Plant Biology, Université de Liege, Liege, Belgium.
Plant Physiol. 2000 Dec;124(4):1678-96. doi: 10.1104/pp.124.4.1678.
The etioplast of dark-grown angiosperms is characterized by the prolamellar body (PLB) inner membrane, the absence of chlorophyll, and the accumulation of divinyl and monovinyl derivatives of protochlorophyll(ide) a [Pchl(ide) a]. Either of two structurally related, but differentially expressed light-dependent NADPH:Pchlide oxidoreductases (PORs), PORA and PORB, can assemble the PLB and form dark-stable ternary complexes containing enzymatically photoactive Pchlide-F655. Here we have examined in detail whether these polypeptides play redundant roles in etioplast differentiation by manipulating the total POR content and the PORA-to-PORB ratio of etiolated Arabidopsis seedlings using antisense and overexpression approaches. POR content correlates closely with PLB formation, the amounts, spectroscopic properties, and photoreduction kinetics of photoactive Pchlide, the ratio of photoactive Pchlide-F655 to non-photoactive Pchl(ide)-F632, and the ratio of divinyl- to monovinyl-Pchl(ide). This last result defines POR as the first endogenous protein factor demonstrated to influence the chemical heterogeneity of Pchl(ide) in angiosperms. It is intriguing that excitation energy transfer between different spectroscopic forms of Pchl(ide) in etiolated cotyledons remains largely independent of POR content. We therefore propose that the PLB contains a minimal structural unit with defined pigment stoichiometries, within which a small amount of non-photoactive Pchl(ide) transfers excitation energy to a large excess of photoactive Pchlide-F655. In addition, our data suggests that POR may bind not only stoichiometric amounts of photoactive Pchlide, but also substoichiometric amounts of non-photoactive Pchl(ide). We conclude that the typical characteristics of etioplasts are closely related to total POR content, but not obviously to the specific presence of PORA or PORB.
黑暗生长的被子植物的黄化质体的特征是原片层体（PLB）内膜、缺乏叶绿素以及原叶绿素（酯）a [Pchl(ide) a] 的二乙烯基和单乙烯基衍生物的积累。两种结构相关但差异表达的光依赖性NADPH：原叶绿素酸酯氧化还原酶（PORs），即PORA和PORB，都可以组装PLB并形成含有酶促光活性Pchlide-F655的黑暗稳定三元复合物。在这里，我们通过使用反义技术和过表达方法来操纵拟南芥黄化幼苗的总POR含量以及PORA与PORB的比例，详细研究了这些多肽在黄化质体分化中是否发挥冗余作用。POR含量与PLB形成、光活性Pchlide的数量、光谱特性和光还原动力学、光活性Pchlide-F655与非光活性Pchl(ide)-F632的比例以及二乙烯基-与单乙烯基-Pchl(ide)的比例密切相关。最后一个结果将POR定义为第一个被证明影响被子植物中Pchl(ide)化学异质性的内源性蛋白质因子。有趣的是，黄化子叶中不同光谱形式的Pchl(ide)之间的激发能量转移在很大程度上仍然与POR含量无关。因此，我们提出PLB包含一个具有确定色素化学计量的最小结构单元，在该单元内，少量的非光活性Pchl(ide)将激发能量转移到大量过量的光活性Pchlide-F655。此外，我们的数据表明，POR不仅可以结合化学计量的光活性Pchlide，还可以结合亚化学计量的非光活性Pchl(ide)。我们得出结论，黄化质体的典型特征与总POR含量密切相关，但与PORA或PORB的具体存在没有明显关系。
