Wu K J, Wang D, Ding J, Yang S H, Zhang X H
State Key Laboratory of Pharmaceutical Biotechnology, Department of Biology, School of Life Sciences, Nanjing University, Nanjing, China.
Genet Mol Res. 2013 Jun 13;12(2):1882-96. doi: 10.4238/2013.January.9.1.
Cytochrome b5 (cyt b5) genes encode ubiquitous electron transport hemoproteins found in animals, plants, fungi, and purple bacteria. However, little is known about their evolutionary history in genomes so far. Here, we conducted an extensive genome-wide survey of cyt b5 genes in 20 representative model species and identified 310 of these genes. Both the absolute number and relative proportion of cyt b5 genes in Paramecium tetraurelia were significantly higher than those in other genomes. Our data also showed that whole-genome duplications (WGDs), especially the recent WGD, contributed to the species-specific expansion of cyt b5 genes in the Paramecium genome. Furthermore, 24 cyt b5 genes were identified as the minimal number of ancestral cyt b5 in the ancestral Paramecium genome, which is also the largest number of these genes encountered in an organism. These results suggest that an excess of cyt b5 genes were selectively retained in this species even before the three WGDs took place. Although more cyt b5 genes were retained in P. tetraurelia than in other genomes, more cyt b5 losses were also observed in the P. tetraurelia genome, suggesting that the balance of gene retention and loss maintained an optimum dosage of cyt b5 genes.
细胞色素b5（cyt b5）基因编码在动物、植物、真菌和紫色细菌中普遍存在的电子传递血蛋白。然而，迄今为止，人们对它们在基因组中的进化历史知之甚少。在此，我们对20个代表性模式物种的cyt b5基因进行了广泛的全基因组调查，共鉴定出310个此类基因。四膜虫（Paramecium tetraurelia）中cyt b5基因的绝对数量和相对比例均显著高于其他基因组。我们的数据还表明，全基因组复制（WGDs），尤其是最近的一次WGD，促成了四膜虫基因组中cyt b5基因的物种特异性扩增。此外，24个cyt b5基因被确定为四膜虫祖先基因组中祖先cyt b5的最小数量，这也是在一个生物体中发现的此类基因的最大数量。这些结果表明，即使在三次WGD发生之前，该物种中就已经选择性地保留了过量的cyt b5基因。虽然四膜虫中保留的cyt b5基因比其他基因组中的多，但在四膜虫基因组中也观察到了更多的cyt b5基因丢失，这表明基因保留和丢失的平衡维持了cyt b5基因的最佳剂量。
