Barker Michael S, Li Zheng, Kidder Thomas I, Reardon Chris R, Lai Zhao, Oliveira Luiz O, Scascitelli Moira, Rieseberg Loren H
Department of Ecology & Evolutionary Biology, University of Arizona, P. O. Box 210088, Tucson, Arizona 85721 USA
Department of Ecology & Evolutionary Biology, University of Arizona, P. O. Box 210088, Tucson, Arizona 85721 USA.
Am J Bot. 2016 Jul;103(7):1203-11. doi: 10.3732/ajb.1600113. Epub 2016 Jun 16.
Like many other flowering plants, members of the Compositae (Asteraceae) have a polyploid ancestry. Previous analyses found evidence for an ancient duplication or possibly triplication in the early evolutionary history of the family. We sought to better place this paleopolyploidy in the phylogeny and assess its nature.
We sequenced new transcriptomes for Barnadesia, the lineage sister to all other Compositae, and four representatives of closely related families. Using a recently developed algorithm, MAPS, we analyzed nuclear gene family phylogenies for evidence of paleopolyploidy.
We found that the previously recognized Compositae paleopolyploidy is also in the ancestry of the Calyceraceae. Our phylogenomic analyses uncovered evidence for a successive second round of genome duplication among all sampled Compositae except Barnadesia.
Our analyses of new samples with new tools provide a revised view of paleopolyploidy in the Compositae. Together with results from a high density Lactuca linkage map, our results suggest that the Compositae and Calyceraceae have a common paleotetraploid ancestor and that most Compositae are descendants of a paleohexaploid. Although paleohexaploids have been previously identified, this is the first example where the paleotetraploid and paleohexaploid lineages have survived over tens of millions of years. The complex polyploidy in the ancestry of the Compositae and Calyceraceae represents a unique opportunity to study the long-term evolutionary fates and consequences of different ploidal levels.
与许多其他开花植物一样，菊科（菊苣科）植物具有多倍体祖先。先前的分析发现了该科早期进化历史中存在古老的加倍事件，甚至可能是三倍化事件的证据。我们试图在系统发育中更准确地定位这种古多倍体现象，并评估其性质。
我们对菊科其他所有类群的姊妹谱系巴纳德菊属以及四个近缘科的代表进行了新的转录组测序。使用最近开发的算法MAPS，我们分析了核基因家族系统发育，以寻找古多倍体的证据。
我们发现，先前确认的菊科古多倍体现象也存在于萼角花科的祖先中。我们的系统基因组分析发现，除巴纳德菊属外，所有采样的菊科植物中都存在连续第二轮基因组加倍的证据。
我们使用新工具对新样本进行的分析提供了关于菊科古多倍体现象的修正观点。结合高密度莴苣连锁图谱的结果，我们的结果表明，菊科和萼角花科有一个共同的古四倍体祖先，并且大多数菊科植物是古六倍体的后代。尽管先前已经鉴定出古六倍体，但这是古四倍体和古六倍体系谱在数千万年中存活下来的首个例子。菊科和萼角花科祖先中的复杂多倍体现象为研究不同倍性水平的长期进化命运和后果提供了独特的机会。
