Evolutionary Patterns of Thylakoid Architecture in Cyanobacteria
Evolutionary Patterns of Thylakoid Architecture in Cyanobacteria
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DOI：
10.3389/fmicb.2019.00277
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发表时间：
2019-02-22
影响因子：
5.2
通讯作者：
Wiedermannova, Jana
中科院分区：
文献类型：
--
作者：
Mares, Jan;Strunecky, Otakar;Wiedermannova, Jana
虽然光合作用过程已越来越多地了解蓝藻模式菌株，不同谱系之间的类囊体膜的空间分布的差异在很大程度上尚未探索。蓝藻细胞的类囊体排列具有多样性，从简单的壁层到放射状、卷曲状、平行状和特殊类型。虽然它们的变异性的代谢背景仍然未知，但已经表明类囊体模式在某些系统发育分支中是稳定的。几十年来，类囊体排列一直被用于蓝藻分类，作为分类群定义的关键特征之一。上一次针对它们在蓝藻中进化历史的综合研究是在15年前发表的。从那时起，DNA序列和电子显微镜数据都迅速增长。在目前的研究中，我们将>200株菌株的超微结构数据映射到SSU rRNA基因树上，并将所得的同源性与同源基因组树进行比较。类囊体结构的变化一般遵循管家基因座的遗传。壁排列被解析为原始的类囊体组织，在大多数衍生的异型细胞蓝藻中演变为复杂的排列。蓝细菌占据中间系统发育的位置（greeter丝状，球状，baeocytous类型）表现出束状，放射状和平行的安排，部分跟踪重建过程中的系统发育分支。与以往的研究相反，类囊体形态的分类学价值似乎非常有限。只有特殊情况下，如类囊体的缺乏或平行排列可以作为分类信息的无型。系统发育树提供的证据都paraphyly和逆转从更衍生的架构在简单的壁类囊体模式。重复收敛进化建议为放射状和束状架构。此外，类囊体的安排受到细胞大小的限制，不包括发生在蓝藻小于2 μ m的宽度复杂的架构。它可能进一步依赖于未知的（生态）生理因素，建议复发的放射状的类型在不相关的，但形态相似的蓝藻，并发生特殊功能的整个发育。参与光合作用和类囊体形成的蛋白质和类囊体模式之间没有直接的系统发育一致性。值得注意的是，一些假设的类囊体生物合成因子部分或完全缺失的蓝藻，挑战他们提出的重要作用。
While photosynthetic processes have become increasingly understood in cyanobacterial model strains, differences in the spatial distribution of thylakoid membranes among various lineages have been largely unexplored. Cyanobacterial cells exhibit an intriguing diversity in thylakoid arrangements, ranging from simple parietal to radial, coiled, parallel, and special types. Although metabolic background of their variability remains unknown, it has been suggested that thylakoid patterns are stable in certain phylogenetic clades. For decades, thylakoid arrangements have been used in cyanobacterial classification as one of the crucial characters for definition of taxa. The last comprehensive study addressing their evolutionary history in cyanobacteria was published 15 years ago. Since then both DNA sequence and electron microscopy data have grown rapidly. In the current study, we map ultrastructural data of >200 strains onto the SSU rRNA gene tree, and the resulting phylogeny is compared to a phylogenomic tree. Changes in thylakoid architecture in general follow the phylogeny of housekeeping loci. Parietal arrangement is resolved as the original thylakoid organization, evolving into complex arrangement in the most derived group of heterocytous cyanobacteria. Cyanobacteria occupying intermediate phylogenetic positions (greeter filamentous, coccoid, and baeocytous types) exhibit fascicular, radial, and parallel arrangements, partly tracing the reconstructed course of phylogenetic branching. Contrary to previous studies, taxonomic value of thylakoid morphology seems very limited. Only special cases such as thylakoid absence or the parallel arrangement could be used as taxonomically informative apomorphies. The phylogenetic trees provide evidence of both paraphyly and reversion from more derived architectures in the simple parietal thylakoid pattern. Repeated convergent evolution is suggested for the radial and fascicular architectures. Moreover, thylakoid arrangement is constrained by cell size, excluding the occurrence of complex architectures in cyanobacteria smaller than 2 mu m in width. It may further be dependent on unknown (eco)physiological factors as suggested by recurrence of the radial type in unrelated but morphologically similar cyanobacteria, and occurrence of special features throughout the phylogeny. No straightforward phylogenetic congruences have been found between proteins involved in photosynthesis and thylakoid formation, and the thylakoid patterns. Remarkably, several postulated thylakoid biogenesis factors are partly or completely missing in cyanobacteria, challenging their proposed essential roles.