Rampant gene loss in the underground orchid Rhizanthella gardneri highlights evolutionary constraints on plastid genomes.
Rampant gene loss in the underground orchid Rhizanthella gardneri highlights evolutionary constraints on plastid genomes.
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DOI：
10.1093/molbev/msr028
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发表时间：
2011-07
影响因子：
10.7
通讯作者：
Small I
中科院分区：
文献类型：
--
作者：
Delannoy E;Fujii S;Colas des Francs-Small C;Brundrett M;Small I
自20亿年前蓝藻叶绿体的内共生起源以来，质体的进化一直以基因的大量丢失为特征。大多数植物和藻类依赖光合作用获得能量，并且在它们的叶绿体基因组中保留了编码基因表达机制和光系统亚基的基因。然而，非光合作用的寄生植物保留了一个简化的质体基因组，表明质体除了光合作用外还有其他基本功能。我们测序了地下兰花Rhizanthella gardneri的完整质体基因组。这种非凡的寄生地下兰花拥有迄今为止在陆地植物中描述的最小的细胞器基因组。在59，190 bp中只有20个蛋白质，4个rRNA和9个tRNA编码，它是迄今为止已知的基因最少的质体基因组，除了一些甲藻的碎片质体基因组。尽管存在许多差异，但与来自无关寄生植物的质体基因组的惊人相似性确定了驻留在植物质体中所需的最小的一组蛋白质编码和tRNA基因。这个趋同进化的最好例子意味着对基因丢失或转移的共同选择性约束。
Since the endosymbiotic origin of chloroplasts from cyanobacteria 2 billion years ago, the evolution of plastids has been characterized by massive loss of genes. Most plants and algae depend on photosynthesis for energy and have retained ∼110 genes in their chloroplast genome that encode components of the gene expression machinery and subunits of the photosystems. However, nonphotosynthetic parasitic plants have retained a reduced plastid genome, showing that plastids have other essential functions besides photosynthesis. We sequenced the complete plastid genome of the underground orchid, Rhizanthella gardneri. This remarkable parasitic subterranean orchid possesses the smallest organelle genome yet described in land plants. With only 20 proteins, 4 rRNAs, and 9 tRNAs encoded in 59,190 bp, it is the least gene-rich plastid genome known to date apart from the fragmented plastid genome of some dinoflagellates. Despite numerous differences, striking similarities with plastid genomes from unrelated parasitic plants identify a minimal set of protein-encoding and tRNA genes required to reside in plant plastids. This prime example of convergent evolution implies shared selective constraints on gene loss or transfer.
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