Wang Jianli, Lee Alison P, Kodzius Rimantas, Brenner Sydney, Venkatesh Byrappa
Mol Biol Evol. 2009 Mar;26(3):487-90. doi: 10.1093/molbev/msn278. Epub 2008 Dec 3.
Stephen (2008) identified 13,736 ultraconserved elements (UCEs) in placental mammals and investigated their evolution in opossum, chicken, frog, and fugu. They found that there was a massive expansion of UCEs during tetrapod evolution and the substitution rate in UCEs showed a significant decline in tetrapods compared with fugu, suggesting they were exapted in tetrapods. They considered it unlikely that these elements are ancient but evolved at a higher rate in teleost fishes. In this study, we investigated the evolution of UCEs in a cartilaginous fish, the elephant shark and show that nearly half the UCEs were present in the jawed vertebrate ancestor. The substitution rate in UCEs is higher in fugu than in elephant shark, and approximately one-third of ancient UCEs have diverged beyond recognition in teleost fishes. These data indicate that UCEs have evolved at a higher rate in teleost fishes, which may have implications for their vast diversity and evolutionary success.
斯蒂芬（2008年）在胎盘哺乳动物中识别出13736个超保守元件（UCE），并研究了它们在负鼠、鸡、青蛙和河豚中的进化情况。他们发现，在四足动物进化过程中UCE出现了大量扩增，并且与河豚相比，四足动物中UCE的替代率显著下降，这表明它们在四足动物中被适应性利用。他们认为这些元件不太可能是古老的，而是在硬骨鱼类中以更高的速率进化。在本研究中，我们研究了软骨鱼类姥鲨中UCE的进化情况，结果表明近一半的UCE存在于有颌脊椎动物的祖先中。河豚中UCE的替代率高于姥鲨，并且大约三分之一的古老UCE在硬骨鱼类中已经分化到无法识别的程度。这些数据表明，UCE在硬骨鱼类中以更高的速率进化，这可能对它们的广泛多样性和进化成功具有重要意义。
