Lineage-Specific Reductions of Plastid Genomes in an Orchid Tribe with Partially and Fully Mycoheterotrophic Species.
Lineage-Specific Reductions of Plastid Genomes in an Orchid Tribe with Partially and Fully Mycoheterotrophic Species.
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具有部分和完全真菌异养物种的兰花部落中质体基因组的谱系特异性减少
DOI：
10.1093/gbe/evw144
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发表时间：
2016-08-03
影响因子：
3.3
通讯作者：
Jin XH
中科院分区：
文献类型：
--
作者：
Feng YL;Wicke S;Li JW;Han Y;Lin CS;Li DZ;Zhou TT;Huang WC;Huang LQ;Jin XH
异养植物如真菌异养菌和寄生虫的质体基因组（质体组）显示出大量的基因丢失，结果是光合作用功能限制的放松。为了了解这种聚合质体减少综合征在异养植物的模式，我们研究了12个密切相关的兰花的三种不同的生活型的族Neottieae（兰科）。我们采用比较基因组学的方法来研究Neottieae内质体的结构和选择性变化。有叶和无叶的异养物种都具有功能减少的质体基因组。我们的分析表明，NAD（P）H脱氢酶复合物、光系统和RNA聚合酶的基因在功能上已经多次独立地丢失。物理还原以高度谱系特异性的方式进行，伴随着结构重构，如大反向重复序列的倒位或修饰。尽管有重大但微小的选择变化，所有保留的基因继续在纯化选择下进化。所有无叶Neottia属物种，包括明显的绿色和非绿色成员，是完全的真菌异养，可能进化自多叶和部分真菌异养物种。Neottieae的质体跨越质体降解的许多阶段，包括最长的质体的一个真菌异养，提供了宝贵的见解质体进化的机制沿着从自养到完全的真菌异养。
The plastid genome (plastome) of heterotrophic plants like mycoheterotrophs and parasites shows massive gene losses in consequence to the relaxation of functional constraints on photosynthesis. To understand the patterns of this convergent plastome reduction syndrome in heterotrophic plants, we studied 12 closely related orchids of three different lifeforms from the tribe Neottieae (Orchidaceae). We employ a comparative genomics approach to examine structural and selectional changes in plastomes within Neottieae. Both leafy and leafless heterotrophic species have functionally reduced plastid genome. Our analyses show that genes for the NAD(P)H dehydrogenase complex, the photosystems, and the RNA polymerase have been lost functionally multiple times independently. The physical reduction proceeds in a highly lineage-specific manner, accompanied by structural reconfigurations such as inversions or modifications of the large inverted repeats. Despite significant but minor selectional changes, all retained genes continue to evolve under purifying selection. All leafless Neottia species, including both visibly green and nongreen members, are fully mycoheterotrophic, likely evolved from leafy and partially mycoheterotrophic species. The plastomes of Neottieae span many stages of plastome degradation, including the longest plastome of a mycoheterotroph, providing invaluable insights into the mechanisms of plastome evolution along the transition from autotrophy to full mycoheterotrophy.