Vinogradov Alexander E, Anatskaya Olga V
Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Avenue 4, St Petersburg 194064, Russia.
Proc Biol Sci. 2006 Jan 7;273(1582):27-32. doi: 10.1098/rspb.2005.3266.
We show the negative link between genome size and metabolic intensity in tetrapods, using the heart index (relative heart mass) as a unified indicator of metabolic intensity in poikilothermal and homeothermal animals. We found two separate regression lines of heart index on genome size for reptiles-birds and amphibians-mammals (the slope of regression is steeper in reptiles-birds). We also show a negative correlation between GC content and nucleosome formation potential in vertebrate DNA, and, consistent with this relationship, a positive correlation between genome GC content and nuclear size (independent of genome size). It is known that there are two separate regression lines of genome GC content on genome size for reptiles-birds and amphibians-mammals: reptiles-birds have the relatively higher GC content (for their genome sizes) compared to amphibians-mammals. Our results suggest uniting all these data into one concept. The slope of negative regression between GC content and nucleosome formation potential is steeper in exons than in non-coding DNA (where nucleosome formation potential is generally higher), which indicates a special role of non-coding DNA for orderly chromatin organization. The chromatin condensation and nuclear size are supposed to be key parameters that accommodate the effects of both genome size and GC content and connect them with metabolic intensity. Our data suggest that the reptilian-birds clade evolved special relationships among these parameters, whereas mammals preserved the amphibian-like relationships. Surprisingly, mammals, although acquiring a more complex general organization, seem to retain certain genome-related properties that are similar to amphibians. At the same time, the slope of regression between nucleosome formation potential and GC content is steeper in poikilothermal than in homeothermal genomes, which suggests that mammals and birds acquired certain common features of genomic organization.
我们利用心脏指数（相对心脏质量）作为变温动物和恒温动物代谢强度的统一指标，展示了四足动物基因组大小与代谢强度之间的负相关关系。我们发现爬行动物 - 鸟类和两栖动物 - 哺乳动物的心脏指数与基因组大小存在两条独立的回归线（爬行动物 - 鸟类的回归线斜率更陡）。我们还展示了脊椎动物DNA中GC含量与核小体形成潜力之间的负相关，并且与此关系一致，基因组GC含量与核大小之间存在正相关（与基因组大小无关）。已知爬行动物 - 鸟类和两栖动物 - 哺乳动物的基因组GC含量与基因组大小存在两条独立的回归线：与两栖动物 - 哺乳动物相比，爬行动物 - 鸟类（就其基因组大小而言）具有相对较高的GC含量。我们的结果表明将所有这些数据整合为一个概念。外显子中GC含量与核小体形成潜力之间的负回归斜率比非编码DNA中更陡（非编码DNA中核小体形成潜力通常更高），这表明非编码DNA在有序染色质组织中具有特殊作用。染色质凝聚和核大小被认为是适应基因组大小和GC含量影响并将它们与代谢强度联系起来的关键参数。我们的数据表明，爬行动物 - 鸟类进化枝在这些参数之间形成了特殊关系，而哺乳动物保留了类似两栖动物的关系。令人惊讶的是，哺乳动物虽然获得了更复杂的总体组织，但似乎保留了某些与两栖动物相似的基因组相关特性。同时，变温动物基因组中核小体形成潜力与GC含量之间的回归斜率比恒温动物基因组中更陡，这表明哺乳动物和鸟类获得了基因组组织的某些共同特征。
