New insights into the nature and phylogeny of prasinophyte antenna proteins:: Ostreococcus tauri, a case study
New insights into the nature and phylogeny of prasinophyte antenna proteins:: Ostreococcus tauri, a case study
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DOI：
10.1093/molbev/msi220
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发表时间：
2005-11-01
影响因子：
10.7
通讯作者：
Partensky, F
中科院分区：
文献类型：
--
作者：
Six, C;Worden, AZ;Partensky, F
Mamiellales （Prasinophyceae）在绿色系中的基础位置使这些单细胞生物成为阐明叶绿素a/b结合光捕获复合物（lhc）进化早期阶段的关键。在这里，我们基于全基因组测序的结果，揭示了牛链球菌（Ostreococcus tauri）中Lhc蛋白的完整和意想不到的多样性。与鳞曼氏曼氏菌一样，金牛单胞菌拥有许多编码一种罕见的葡萄球菌特异性Lhc蛋白类型的基因，本文将其命名为“Lhcp”。这些复合物的生化表征表明，这些多肽结合叶绿素a、b和叶绿素c样色素（mg -2,4-二乙烯基-卟啉a(5)单甲基酯）以及一些不寻常的类胡萝卜素，可能是主要的。它们在反应中心I (RCI)-和RCI富集组分中都有一定程度的回收，这表明它们可能与两种光系统有关。然而，与以往关于鳞状m.s squamata LHC的报道形成鲜明对比的是，牛牛也具有其他LHC亚群，包括LHCI蛋白（由五个不同的Lhca基因编码）和次要的LHCII多肽CP26和CP29。利用一种抗植物Lhca2的抗体，我们明确地表明，LHCI蛋白不仅存在于牛头牛中（它们可能与RCI相关），也存在于其他哺乳动物中，包括M. squamata。除Lhcp基因外，所有已鉴定的Lhc基因仅存在于单拷贝中。总的来说，在这些裸生植物中发现了LHCI蛋白，再加上在高等植物或其他绿藻中发现的主要LHCII多肽的缺乏，支持了后者蛋白在LHCI蛋白之后出现的假设。叶绿素植物的主要LHC可能先于其他含叶绿素a/b的生物的LHCII出现，可能是由于LHCI基因前体的分化。然而，在O. tauri中发现的cp26样蛋白，在系统发育上位于主要LHCII蛋白分支的底部，为这些天线蛋白的起源提供了新的见解，这些天线蛋白在高等植物和绿藻中分别进化。其多样化但数量有限的大型强子对撞机基因套件使金牛O. tauri成为未来研究大型强子对撞机组件进化和功能的特殊模型系统。
The basal position of the Mamiellales (Prasinophyceae) within the green lineage makes these unicellular organisms key to elucidating early stages in the evolution of chlorophyll a/b-binding light-harvesting complexes (LHCs). Here, we unveil the complete and unexpected diversity of Lhc proteins in Ostreococcus tauri, a member of the Mamiellales order, based on results from complete genome sequencing. Like Mantoniella squamata, O. tauri possesses a number of genes encoding an unusual prasinophyte-specific Lhc protein type herein designated "Lhcp". Biochemical characterization of the complexes revealed that these polypeptides, which bind chlorophylls a, b, and a chlorophyll c-like pigment (Mg-2,4-divinyl-phaeoporphyrin a(5) monomethyl ester) as well as a number of unusual carotenoids, are likely predominant. They are retrieved to some extent in both reaction center I (RCI)- and RCII-enriched fractions, suggesting a possible association to both photosystems. However, in sharp contrast to previous reports on LHCs of M. squamata, O. tauri also possesses other LHC subpopulations, including LHCI proteins (encoded by five distinct Lhca genes) and the minor LHCII polypeptides, CP26 and CP29. Using an antibody against plant Lhca2, we unambiguously show that LHCI proteins are present not only in O. tauri, in which they are likely associated to RCI, but also in other Mamiellales, including M. squamata. With the exception of Lhcp genes, all the identified Lhc genes are present in single copy only. Overall, the discovery of LHCI proteins in these prasinophytes, combined with the lack of the major LHCII polypeptides found in higher plants or other green algae, supports the hypothesis that the latter proteins appeared subsequent to LHCI proteins. The major LHC of prasinophytes might have arisen prior to the LHCII of other chlorophyll a/b-containing organisms, possibly by divergence of a LHCI gene precursor. However, the discovery in O. tauri of CP26-like proteins, phylogenetically placed at the base of the major LHCII protein clades, yields new insight to the origin of these antenna proteins, which have evolved separately in higher plants and green algae. Its diverse but numerically limited suite of Lhc genes renders O. tauri an exceptional model system for future research on the evolution and function of LHC components.