Department of Horticulture, University of Wisconsin, Madison, WI 53706, USA.
Theor Appl Genet. 2012 Jun;125(1):11-8. doi: 10.1007/s00122-012-1812-z. Epub 2012 Feb 21.
Mitochondria are organelles that have their own DNA; serve as the powerhouses of eukaryotic cells; play important roles in stress responses, programmed cell death, and ageing; and in the vast majority of eukaryotes, are maternally transmitted. Strict maternal transmission of mitochondria makes it difficult to select for better-performing mitochondria, or against deleterious mutations in the mitochondrial DNA. Cucumber is a useful plant for organellar genetics because its mitochondria are paternally transmitted and it possesses one of the largest mitochondrial genomes among all eukaryotes. Recombination among repetitive motifs in the cucumber mitochondrial DNA produces rearrangements associated with strongly mosaic (MSC) phenotypes. We previously reported nuclear control of sorting among paternally transmitted mitochondrial DNAs. The goal of this project was to map paternal sorting of mitochondria as a step towards its eventual cloning. We crossed single plants from plant introduction (PI) 401734 and Cucumis sativus var. hardwickii and produced an F(2) family. A total of 425 F(2) plants were genotyped for molecular markers and testcrossed as the female with MSC16. Testcross families were scored for frequencies of wild-type versus MSC progenies. Discrete segregations for percent wild-type progenies were not observed and paternal sorting of mitochondria was therefore analyzed as a quantitative trait. A major quantitative trait locus (QTL; LOD >23) was mapped between two simple sequence repeats encompassing a 459-kb region on chromosome 3. Nuclear genes previously shown to affect the prevalence of mitochondrial DNAs (MSH1, OSB1, and RECA homologs) were not located near this major QTL on chromosome 3. Sequencing of this region from PI 401734, together with improved annotation of the cucumber genome, should result in the eventual cloning of paternal sorting of mitochondria and provide insights about nuclear control of organellar-DNA sorting.
线粒体是具有自身 DNA 的细胞器；是真核细胞的“动力工厂”；在应激反应、程序性细胞死亡和衰老中发挥重要作用；在绝大多数真核生物中，通过母系遗传。线粒体严格的母系遗传使得选择性能更好的线粒体或对抗线粒体 DNA 中的有害突变变得困难。黄瓜是细胞器遗传学的有用植物，因为其线粒体通过父系遗传，并且拥有所有真核生物中最大的线粒体基因组之一。黄瓜线粒体 DNA 中重复序列之间的重组产生了与强烈镶嵌（MSC）表型相关的重排。我们之前报道了核控制父系传递的线粒体的分拣。该项目的目标是绘制父系分拣线粒体的图谱，作为其最终克隆的一个步骤。我们从植物引种（PI）401734 和 Cucumis sativus var. hardwickii 中杂交了单个植物，并产生了一个 F(2)家系。总共对 425 株 F(2)植物进行了分子标记的基因型分析，并作为雌性与 MSC16 进行了测交。对 MSC16 的测交家系进行了野生型与 MSC 后代频率的评分。没有观察到离散的野生型后代分离，因此线粒体的父系分拣被分析为一种数量性状。在染色体 3 上的两个简单重复序列之间，映射到一个包含 459-kb 区域的主要数量性状位点（LOD >23）。先前显示影响线粒体 DNA 流行率的核基因（MSH1、OSB1 和 RECA 同源物）不在染色体 3 上这个主要 QTL 附近。从 PI 401734 中对该区域进行测序，以及对黄瓜基因组的改进注释，应该最终导致线粒体父系分拣的克隆，并提供关于核控制细胞器 DNA 分拣的见解。
