Sheppard Anna E, Ayliffe Michael A, Blatch Laura, Day Anil, Delaney Sven K, Khairul-Fahmy Norfarhana, Li Yuan, Madesis Panagiotis, Pryor Anthony J, Timmis Jeremy N
School of Molecular and Biomedical Science, University of Adelaide, South Australia 5005, Australia.
Plant Physiol. 2008 Sep;148(1):328-36. doi: 10.1104/pp.108.119107. Epub 2008 Jul 25.
In eukaryotes, many genes were transferred to the nucleus from prokaryotic ancestors of the cytoplasmic organelles during endosymbiotic evolution. In plants, the transfer of genetic material from the plastid (chloroplast) and mitochondrion to the nucleus is a continuing process. The cellular location of a kanamycin resistance gene tailored for nuclear expression (35SneoSTLS2) was monitored in the progeny of reciprocal crosses of tobacco (Nicotiana tabacum) in which, at the start of the experiments, the reporter gene was confined either to the male or the female parental plastid genome. Among 146,000 progeny from crosses where the transplastomic parent was male, 13 transposition events were identified, whereas only one atypical transposition was identified in a screen of 273,000 transplastomic ovules. In a second experiment, a transplastomic beta-glucuronidase reporter gene, tailored to be expressed only in the nucleus, showed frequent stochastic expression that was confined to the cytoplasm in the somatic cells of several plant tissues. This gene was stably transferred in two out of 98,000 seedlings derived from a male transplastomic line crossed with a female wild type. These data demonstrate relocation of plastid DNA to the nucleus in both somatic and gametophytic tissue and reveal a large elevation of the frequency of transposition in the male germline. The results suggest a new explanation for the occurrence of uniparental inheritance in eukaryotes.
在真核生物中，在共生进化过程中，许多基因从细胞质细胞器的原核祖先转移到了细胞核。在植物中，遗传物质从质体（叶绿体）和线粒体向细胞核的转移是一个持续的过程。在烟草（Nicotiana tabacum）正反交后代中，监测了一个为核表达量身定制的卡那霉素抗性基因（35SneoSTLS2）的细胞定位，在实验开始时，报告基因要么局限于雄性亲本质体基因组，要么局限于雌性亲本质体基因组。在转基因父本为雄性的杂交后代的146,000个后代中，鉴定出13个转位事件，而在对273,000个转基因胚珠的筛选中仅鉴定出1个非典型转位。在第二个实验中，一个仅为在细胞核中表达而定制的转基因β-葡萄糖醛酸酶报告基因，在几种植物组织的体细胞中表现出频繁的随机表达，且局限于细胞质。在一个雄性转基因品系与雌性野生型杂交产生的98,000株幼苗中，有2株该基因稳定转移。这些数据证明了质体DNA在体细胞和配子体组织中都向细胞核的重新定位，并揭示了雄性生殖系中转位频率的大幅提高。这些结果为真核生物中单亲遗传的发生提出了一种新的解释。
