White M M, McLaren I A
Department of Biology, Dalhousie University, Halifax, Canada.
Genome. 2000 Oct;43(5):750-5. doi: 10.1139/g00-048.
It is known that body sizes and temperature-independent developmental durations within two genera of calanoid Copepoda (Crustacea) are positively related to nuclear DNA contents of their somatic nuclei. Evidently because of the constraint of similar cell numbers among the species, (nucleotypic) effects of nucleus size on cell size and on cell-level processes are expressed at the whole-organism level. Here, we show that developmental durations of eight species of five genera are also negatively related to their greatly differing numbers of 18S rRNA genes per unit DNA. We propose that levels of rDNA iteration among copepods have been controlled by natural selection to regulate ribosome concentrations, therefore protein production and development rates, independently of the large variations in genome sizes, which are in turn adapted to regulating cell and therefore body sizes.
已知哲水蚤目（甲壳纲）两个属内的体型大小和与温度无关的发育持续时间与它们体细胞核的核DNA含量呈正相关。显然，由于物种间细胞数量相似的限制，细胞核大小对细胞大小和细胞水平过程的（核型）影响在整个生物体水平上得以体现。在此，我们表明五个属的八个物种的发育持续时间也与它们每单位DNA中18S rRNA基因数量的巨大差异呈负相关。我们提出，桡足类动物中rDNA重复水平受自然选择控制，以调节核糖体浓度，从而调节蛋白质产生和发育速率，这独立于基因组大小的巨大变化，而基因组大小的变化反过来又适应于调节细胞进而调节体型大小。
