Evolution of plastid gene rps2 in a lineage of hemiparasitic and holoparasitic plants: Many losses of photosynthesis and complex patterns of rate variation
Evolution of plastid gene rps2 in a lineage of hemiparasitic and holoparasitic plants: Many losses of photosynthesis and complex patterns of rate variation
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DOI：
10.1073/pnas.94.14.7367
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发表时间：
1997-07-08
影响因子：
11.1
通讯作者：
Wolfe, AD
中科院分区：
文献类型：
--
作者：
dePamphilis, CW;Young, ND;Wolfe, AD
一些非光合寄生植物的质体基因组经历了基因含量的极度减少和剩余基因进化速率的增加。这些事件的动力学，或者是否是光合作用丧失的直接结果，目前还不清楚。寄生玄参科和列当科，代表了一个连续的异养能力，从光合半寄生虫nonphotosynthetic holoparasites，被用来调查这些问题。我们提出了寄生玄参科和列当科的质体基因rps2，编码的质体核糖体的S2亚基的序列的基础上的系统发育假说。寄生玄参科和列当科形成一个单系群，其中寄生可以推断已经进化了一次。全寄生现象至少已经独立进化了五次，某些全寄生谱系代表单个种、属和非光合属的集合。光合作用基因rbcL的进化损失仅限于一个子集的holoparasitic谱系，与几个holoparasitic保留全长rbcL序列。与此相反，翻译基因rps2保留在所有的植物调查，但经历了几个半，以及holoparasitic谱系的速率加速，这表明可能有大量的分子进化变化的质体基因组的寄生虫光合作用的损失之前。rps2中同义和非同义速率加速的独立模式指向不同谱系中速率变化的不同机制。寄生玄参科（包括传统列当科）为研究其分子进化过程、基因功能和寄生性进化提供了丰富的平台。
The plastid genomes of some nonphotosynthetic parasitic plants have experienced an extreme reduction in gene content and an increase in evolutionary rate of remaining genes. Nothing is known of the dynamics of these events or whether either is a direct outcome of the loss of photosynthesis. The parasitic Scrophulariaceae and Orobanchaceae, representing a continuum of heterotrophic ability ranging from photosynthetic hemiparasites to nonphotosynthetic holoparasites, are used to investigate these issues. We present a phylogenetic hypothesis for parasitic Scrophulariaceae and Orobanchaceae based on sequences of the plastid gene rps2, encoding the S2 subunit of the plastid ribosome. Parasitic Scrophulariaceae and Orobanchaceae form a monophyletic group in which parasitism can be inferred to have evolved once. Holoparasitism has evolved independently at least five times, with certain holoparasitic lineages representing single species, genera, and collections of nonphotosynthetic genera. Evolutionary loss of the photosynthetic gene rbcL is limited to a subset of holoparasitic lineages, with several holoparasites retaining a full length rbcL sequence. In contrast, the translational gene rps2 is retained in all plants investigated but has experienced rate accelerations in several hemi- as well as holoparasitic lineages, suggesting that there may be substantial molecular evolutionary changes to the plastid genome of parasites before the loss of photosynthesis. Independent patterns of synonymous and nonsynonymous rate acceleration in rps2 point to distinct mechanisms underlying rate variation in different lineages. Parasitic Scrophulariaceae (including the traditional Orobanchaceae) provide a rich platform for the investigation of molecular evolutionary process, gene function, and the evolution of parasitism.