THE PLASTID GENOME OF THE MYCOHETEROTROPHIC CORALLORHIZA STRIATA (ORCHIDACEAE) IS IN THE RELATIVELY EARLY STAGES OF DEGRADATION
THE PLASTID GENOME OF THE MYCOHETEROTROPHIC CORALLORHIZA STRIATA (ORCHIDACEAE) IS IN THE RELATIVELY EARLY STAGES OF DEGRADATION
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DOI：
10.3732/ajb.1200256
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发表时间：
2012-09-01
影响因子：
3
通讯作者：
Davis, Jerrold I.
中科院分区：
文献类型：
--
作者：
Barrett, Craig F.;Davis, Jerrold I.
研究前提：质体基因组的非光合作用，mycoheterotrophic植物的apt系统，在其中研究放松进化限制的影响。到目前为止，测序的少数真菌异养被子植物质体显示相对于光合亲属的降解/减少的剧烈模式。本研究的目标是集中在一个mycoheterotrophic兰花假设是在“早期”阶段的质体降解，提供对这个process.Methods：短读测序的观点是用来产生一个完整的质体序列珊瑚根striata变种。vreelandii，一种真菌异养兰花，研究质体降解的程度。模式的非同义/同义突变也进行了评估，并进行了比较珊瑚根和其他异养植物lineage.Key结果：珊瑚根产生了一个137 505 bp的质体，与几个光合作用相关的基因丢失或假基因。所有主要的光合作用复合物的成员，除了ATP合酶基因，受到影响。“管家”基因是完整的，尽管失去了一个tRNA。完整的光合作用基因（不包括ATP基因）一起显示升高的非同义变化，而管家基因没有。结论：珊瑚根质体的整体大小没有大幅减少（类似于6%的减少相对于光合文心兰），但显示一个模式一致的光合功能的损失。比较珊瑚根与其他异养生物允许一些新兴的进化模式进行推断，但这些仍然是假设进行测试，特别是在较低的分类水平，并在谱系说明从自养到异养的过渡。真菌异养谱系中独立的、独特的质体修饰过程说明了其保护的紧迫性。
Premise of the study: Plastid genomes of nonphotosynthetic, mycoheterotrophic plants represent apt systems in which to study effects of relaxed evolutionary constraints. The few mycoheterotrophic angiosperm plastomes sequenced to date display drastic patterns of degradation/reduction relative to those of photosynthetic relatives. The goal of this study was to focus on a mycoheterotrophic orchid hypothesized to be in the "early" stages of plastome degradation, to provide perspective on this process.Methods: Short-read sequencing was used to generate a complete plastome sequence for Corallorhiza striata var. vreelandii, a mycoheterotrophic orchid, to investigate the extent of plastome degradation. Patterns of nonsynonymous/synonymous mutations were also assessed, and comparisons were made between Corallorhiza and other heterotrophic plant lineages.Key results: Corallorhiza yielded a plastome of 137 505 bp, with several photosynthesis-related genes either lost or pseudogenized. Members of all major photosynthesis complexes, except ATP-synthase genes, were affected. "Housekeeping" genes were intact, despite the loss of a single tRNA. Intact photosynthesis genes (excluding atp genes) together displayed elevated nonsynonymous changes, while housekeeping genes did not.Conclusions: The Corallorhiza plastome is not drastically reduced in overall size (similar to 6% reduction relative to that of photosynthetic Oncidium), but displays a pattern congruent with a loss of photosynthetic function. Comparing Corallorhiza with other heterotrophs allows some emergent evolutionary patterns to be inferred, but these remain as hypotheses to be tested, especially at lower taxonomic levels, and in lineages illustrating transitions from autotrophy to heterotrophy. The independent, unique processes of plastome modification among mycoheterotrophic lineages illustrate the urgency of their conservation.