鸟类基因组大小和结构在非鸟类恐龙中的起源
Chris L Organ1, Andrew M Shedlock, Andrew Meade
1Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138, USA. corgan@oeb.harvard.edu
Nature
|March 9, 2007
概括
小型鸟类基因组在鸟类数百万年前的类恐龙中进化. 这表明关键的鸟类特征,如减少的重复性DNA,起源于非鸟类恐龙,而不仅仅是鸟类.
科学领域:
- 进化生物学 进化生物学
- 古遗传学是古遗传学的一部分.
- 进行比较基因组学.
背景情况:
- 与其他羊动物相比,鸟类基因组显著较小和精简,具有较少的重复和非编码DNA元素.
- 这种精简的基因组被假设是适应飞行,减少与大基因组和细胞大小相关的代谢成本.
- 研究基因组进化是具有挑战性的,因为从灭绝的物种基因组数据的稀缺性.
研究的目的:
- 为了研究小鸟类基因组大小的进化起源.
- 估计灭绝的恐龙的基因组大小,包括灭绝的鸟类,使用一种新的比较方法.
- 确定什么时候在恐龙进化过程中发生了鸟类基因组的特征,即重复性DNA的减少.
主要方法:
- 利用一种新的贝叶斯比较方法,将骨细胞大小与现存脊椎动物的基因组大小相关联.
- 应用了这种既定的关系来估计31种灭绝的恐龙物种的基因组大小.
- 分析了比较的基因组数据,以估计灭绝的恐龙血统中全基因组间分散的移动元素的比例.
主要成果:
- 该研究估计,典型的鸟类飞行适应的小基因组在2.3亿至2.5亿年前的类恐龙血统中进化,比第一批鸟类更早.
- 据推断,ornithischian恐龙拥有显著更大的基因组,可能代表了Dinosauria的祖先条件.
- 重复的DNA (间隔的移动元素) 构成了类恐龙的总基因组中较小的部分 (5-12%) 与鸟类恐龙 (7-19%) 相比,这表明前者活动减少.
结论:
- 与鸟类飞行相关的基因组精简起源于非鸟类的类恐龙,早在鸟类的进化之前.
- 这一发现将基因组特征添加到日益增长的特征列表中,如羽毛和先进的呼吸系统,这些特征在非鸟类恐龙中演变.
- 索里斯基动物中重复元素的活性减少代表了朝着紧的鸟类基因组迈出的重大进化步骤.
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