O'Conner Seth, Li Ling
Department of Biological Sciences, Mississippi State University, Mississippi State, MS, United States.
Front Plant Sci. 2020 Dec 3;11:600117. doi: 10.3389/fpls.2020.600117. eCollection 2020.
Plant mitochondrial genomes exhibit unique evolutionary patterns. They have a high rearrangement but low mutation rate, and a large size. Based on massive mitochondrial DNA transfers to the nucleus as well as the mitochondrial unique evolutionary traits, we propose a "Mitochondrial Fostering" theory where the organelle genome plays an integral role in the arrival and development of orphan genes (genes with no homologs in other lineages). Two approaches were used to test this theory: (1) bioinformatic analysis of nuclear mitochondrial DNA (Numts: mitochondrial originating DNA that migrated to the nucleus) at the genome level, and (2) bioinformatic analysis of particular orphan sequences present in both the mitochondrial genome and the nuclear genome of . One study example is given about one orphan sequence that codes for two unique orphan genes: one in the mitochondrial genome and another one in the nuclear genome. DNA alignments show regions of this orphan sequence exist scattered throughout other land plant mitochondrial genomes. This is consistent with the high recombination rates of mitochondrial genomes in land plants. This may also enable the creation of novel coding sequences within the orphan loci, which can then be transferred to the nuclear genome and become exposed to new evolutionary pressures. Our study also reveals a high correlation between the amount of mitochondrial DNA transferred to the nuclear genome and the number of orphan genes in land plants. All the data suggests the mitochondrial genome may play a role in nuclear orphan gene evolution in land plants.
植物线粒体基因组呈现出独特的进化模式。它们具有高度重排但低突变率，且基因组规模较大。基于大量线粒体DNA向细胞核的转移以及线粒体独特的进化特征，我们提出了一种“线粒体培育”理论，即细胞器基因组在孤儿基因（在其他谱系中无同源物的基因）的出现和发展中发挥着不可或缺的作用。我们采用了两种方法来验证这一理论：（1）在基因组水平对核线粒体DNA（Numts：迁移到细胞核的源自线粒体的DNA）进行生物信息学分析，以及（2）对 植物线粒体基因组和核基因组中都存在的特定孤儿序列进行生物信息学分析。给出了一个关于一个孤儿序列的研究实例，该序列编码两个独特的孤儿基因：一个在线粒体基因组中，另一个在核基因组中。DNA比对显示，该孤儿序列的区域分散存在于其他陆地植物线粒体基因组中。这与陆地植物线粒体基因组的高重组率相一致。这也可能促使在孤儿基因座内产生新的编码序列，然后这些序列可转移到核基因组并面临新的进化压力。我们的研究还揭示了转移到核基因组的线粒体DNA数量与陆地植物中孤儿基因数量之间的高度相关性。所有数据表明线粒体基因组可能在陆地植物核孤儿基因的进化中发挥作用。
