Department of Integrative Biology, University of Texas at Austin.
Center of Excellence for Bionanoscience Research, King Abdulaziz University (KAU), Jeddah, Saudi Arabia.
Genome Biol Evol. 2019 Apr 1;11(4):1321-1333. doi: 10.1093/gbe/evz076.
The plant genome comprises a coevolving, integrated genetic system housed in three subcellular compartments: the nucleus, mitochondrion, and the plastid. The typical land plant plastid genome (plastome) comprises the sum of repeating units of 130-160 kb in length. The plastome inverted repeat (IR) divides each plastome monomer into large and small single copy regions, an architecture highly conserved across land plants. There have been varying degrees of expansion or contraction of the IR, and in a few distinct lineages, including the IR-lacking clade of papilionoid legumes, one copy of the IR has been lost. Completion of plastome sequencing and assembly for 19 Medicago species and Trigonella foenum-graceum and comparative analysis with other IR-lacking clade taxa revealed modest divergence with regard to structural organization overall. However, one clade contained unique variation suggesting an ancestor had experienced repeat-mediated changes in plastome structure. In Medicago minima, a novel IR of ∼9 kb was confirmed and the role of repeat-mediated, recombination-dependent replication in IR reemergence is discussed.
植物基因组由三个亚细胞区室（核、线粒体和质体）中的协同进化、整合的遗传系统组成。典型的陆地植物质体基因组（质体基因组）由长度为 130-160kb 的重复单元的总和组成。质体反向重复（IR）将每个质体单体分为大、小单拷贝区，这种结构在陆地植物中高度保守。IR 发生了不同程度的扩张或收缩，在一些独特的谱系中，包括缺少 IR 的豆科植物类群，已经丢失了一个 IR 拷贝。对 19 种紫花苜蓿物种和三叶草的质体基因组测序和组装完成，并与其他缺少 IR 的类群进行了比较分析，结果表明整体结构组织上存在适度的差异。然而，一个类群包含独特的变异，表明其祖先经历了质体结构的重复介导变化。在紫花苜蓿 minuta 中，确认了一个新的约 9kb 的 IR，并讨论了重复介导、重组依赖复制在 IR 重新出现中的作用。
