由加拿大蒙特利尔大学科学家Normand Brisson带领的一组研究人员鉴定出一类能使基因组避免发生有害突变的蛋白。这类蛋白的结构与陀螺十分相似,Brisson证实它们在防止基因发生较大重排以致产生多基因拷贝方面起着重要作用。这些蛋白参与一系列的生物现象,包括病原体防御反应。
科研人员研究了该类蛋白在维持拟南芥质体基因组稳定性方面的作用。研究成果发表于PNAS。他们发现,这类螺旋状的蛋白能与单链DNA分子结合,起到阻止结合的作用,从而保证了质体基因组的完整性。将这类蛋白的编码基因沉默,会使植物叶片出现青白斑,这是叶绿体失效的症状。
研究人员发现,这类蛋白不仅能阻止基因组发生不利转变,而且还允许发生一些有利突变。Brisson说:“这些突变性状如植物高营养价值、抗病性及抗气候变化性等在现代农业中起重要作用。我们的结果为与之相似的人类基因修复机理的研究提供了一种方法,基因修复或许对人类进化、胁迫反应以及预防破坏性疾病等具有重要作用。”(生物谷bioon.com)
生物谷推荐原文出处:
PNAS August 25, 2009 vol. 106 no. 34 14693-14698
Whirly proteins maintain plastid genome stability in Arabidopsis
Alexandre Maréchal,1, Jean-Sébastien Parent,1, Félix Véronneau-Lafortune, Alexandre Joyeux, B. Franz Lang and Normand Brisson,2
Department of Biochemistry, Université de Montréal, P.O. Box 6128, Station Centre-ville, Montréal, QC, Canada H3C 3J7
Maintenance of genome stability is essential for the accurate propagation of genetic information and cell growth and survival. Organisms have therefore developed efficient strategies to prevent DNA lesions and rearrangements. Much of the information concerning these strategies has been obtained through the study of bacterial and nuclear genomes. Comparatively, little is known about how organelle genomes maintain a stable structure. Here, we report that the plastid-localized Whirly ssDNA-binding proteins are required for plastid genome stability in Arabidopsis. We show that a double KO of the genes AtWhy1 and AtWhy3 leads to the appearance of plants with variegated green/white/yellow leaves, symptomatic of nonfunctional chloroplasts. This variegation is maternally inherited, indicating defects in the plastid genome. Indeed, in all variegated lines examined, reorganized regions of plastid DNA are amplified as circular and/or head-tail concatemers. All amplified regions are delimited by short direct repeats of 10–18 bp, strongly suggesting that these regions result from illegitimate recombination between repeated sequences. This type of recombination occurs frequently in plants lacking both Whirlies, to a lesser extent in single KO plants and rarely in WT individuals. Maize mutants for the ZmWhy1 Whirly protein also show an increase in the frequency of illegitimate recombination. We propose a model where Whirlies contribute to plastid genome stability by protecting against illegitimate repeat-mediated recombination.