Early gene duplication within chloroplastida and its correspondence with relocation of starch metabolism to chloroplasts
Early gene duplication within chloroplastida and its correspondence with relocation of starch metabolism to chloroplasts
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DOI：
10.1534/genetics.108.087205
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发表时间：
2008-04-01
期刊：
影响因子：
3.3
通讯作者：
Ball, Steven G.
中科院分区：
文献类型：
--
作者：
Deschamps, Philippe;Moreau, Herve;Ball, Steven G.
内共生事件导致的光合真核生物的质体是伴随着一种新的形式的存储多糖在红藻纲，绿藻门，叶绿体的外观。先前的分析表明，淀粉合成是蓝藻和真核生物贮藏多糖代谢途径合并的结果。我们对六种藻类基因组序列进行了比较生物信息学分析，以调查这种合并。具体而言，我们分析了两个绿藻，莱茵衣藻和团藻，和四个Prasinophytae，两个Ostreococcus菌株和两个Microconas pusilla菌株。我们的分析揭示了一个复杂的代谢途径，其复杂性和功能似乎在整个绿色谱系中是保守的。比较这一途径，最近提出的红藻表明，我们观察到的复杂性是独特的绿色血统，并产生时，后者从红藻分歧。这一发现与叶绿体中淀粉代谢的质体定位相一致。相比之下，红藻纲和蓝绿藻门在细胞质中产生和储存淀粉，并且具有较低的复杂性途径。细胞质淀粉合成目前被假设为代表在古质体储存多糖代谢的祖先状态。将细胞质途径的组分重新定位到质体可能需要一个复杂的逐步过程，涉及几轮基因复制。我们建议，这种搬迁的葡聚糖合成的质体促进进化的叶绿素含捕光复合物天线在叶绿体中发挥保护作用。
The endosymbiosis event resulting in the plastid of photosynthetic eukaryotes was accompanied by the appearance of a novel form of storage polysaccharide in Rhodophyceae, Glaucophyta, and Chloroplastida. Previous analyses indicated that starch synthesis resulted from the merging of the cyanobacterial and the eukaryotic storage polysaccharide metabolism pathways. We performed a comparative bio-informatic analysis of six algal genome sequences to investigate this merger. Specifically, we analyzed two Chlorophyceae, Chlamydomonas reinhardtii and Volvox carterii, and four Prasinophytae, two Ostreococcus strains and two Micromonas pusilla strains. Our analyses revealed a complex metabolic pathway whose intricacies and function seem conserved throughout the green lineage. Comparison of this pathway to that recently proposed for the Rhodophyceae suggests that the complexity that we observed is unique to the green lineage and was generated when the latter diverged from the red algae. This finding corresponds well with the plastidial location of starch metabolism in Chloroplastidae. In contrast, Rhodophyceae and Glaucophyta produce and store starch in the cytoplasm and have a lower complexity pathway. Cytoplasmic starch synthesis is currently hypothesized to represent the ancestral state of storage polysaccharide metabolism in Archaeplastida. The retargeting of components of the cytoplasmic pathway to plastids likely required a complex stepwise process involving several rounds of gene duplications. We propose that this relocation of glucan synthesis to the plastid facilitated evolution of chlorophyll-containing light-harvesting complex antennae by playing a protective role within the chloroplast.