Yudina Sophia V, Schelkunov Mikhail I, Nauheimer Lars, Crayn Darren, Chantanaorrapint Sahut, Hroneš Michal, Sochor Michal, Dančák Martin, Mar Shek-Shing, Luu Hong Truong, Nuraliev Maxim S, Logacheva Maria D
Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
Institute for Information Transmission Problems, Moscow, Russia.
Front Plant Sci. 2021 Mar 16;12:602598. doi: 10.3389/fpls.2021.602598. eCollection 2021.
Heterotrophic plants provide intriguing examples of reductive evolution. This is especially evident in the reduction of their plastid genomes, which can potentially proceed toward complete genome loss. Several milestones at the beginning of this path of degradation have been described; however, little is known about the latest stages of plastome reduction. Here we analyze a diversity of plastid genomes in a set of closely related non-photosynthetic plants. We demonstrate how a gradual loss of genes shapes the miniaturized plastomes of these plants. The subject of our study, the genus , represents the mycoheterotrophic monocot family Thismiaceae, a group that may have experienced a very ancient (60-80 mya) transition to heterotrophy. In all 18 species examined, the plastome is reduced to 14-18 kb and is highly AT-biased. The most complete observed gene set includes , seven ribosomal protein genes, three rRNA, and two tRNA genes. Different clades of have undergone further gene loss (complete absence or pseudogenization) compared to this set: in particular, we report two independent losses of and .
异养植物提供了还原进化的有趣例子。这在它们质体基因组的缩减中尤为明显，质体基因组可能会朝着完全丧失基因组的方向发展。这条降解途径开始阶段的几个里程碑已被描述；然而，对于质体基因组缩减的最后阶段知之甚少。在这里，我们分析了一组密切相关的非光合植物中多种质体基因组。我们展示了基因的逐渐丧失如何塑造这些植物的小型化质体基因组。我们的研究对象是 属，它代表了菌异养单子叶植物水玉簪科，这是一个可能在非常古老的时期（6000 - 8000万年前）就向异养转变的类群。在所研究的全部18个物种中，质体基因组缩减至14 - 18 kb，并且高度偏向于A/T。观察到的最完整基因集包括 、七个核糖体蛋白基因、三个rRNA和两个tRNA基因。与该基因集相比， 的不同分支经历了进一步的基因丧失（完全缺失或假基因化）：特别是，我们报告了 和 的两次独立丧失。
