Liu Jiang, Wang Xiao-ping, Cho Soochin, Lim Burton K, Irwin David M, Ryder Oliver A, Zhang Ya-ping, Yu Li
Laboratory for Conservation and Utilization of Bio-resource & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming 650091, PR China.
Department of Biology, Creighton University, Omaha, Nebraska, United States of America.
Sci Rep. 2014 May 27;4:5070. doi: 10.1038/srep05070.
Pancreatic ribonuclease (RNASE1) is a digestive enzyme that has been one of the key models in studies of evolutionary innovation and functional diversification. It has been believed that the RNASE1 gene duplications are correlated with the plant-feeding adaptation of foregut-fermenting herbivores. Here, we characterized RNASE1 genes from Caniformia, which has a simple digestive system and lacks microbial digestion typical of herbivores, in an unprecedented scope based on both gene sequence and tissue expression analyses. Remarkably, the results yielded new hypotheses regarding the evolution and the function of Caniformia RNASE1 genes. Four independent gene duplication events in the families of superfamily Musteloidea, including Procyonidae, Ailuridae, Mephitidae and Mustelidae, were recovered, rejecting previous Mustelidae-specific duplication hypothesis, but supporting Musteloidea duplication hypothesis. Moreover, our analyses revealed pronounced differences among the RNASE1 gene copies regarding their selection pressures, pI values and tissue expression patterns, suggesting the differences in their physiological functions. Notably, the expression analyses detected the transcription of a RNASE1 pseudogene in several tissues, raising the possibility that pseudogenes are also a potential source during the RNase functional diversification. In sum, the present work demonstrated a far more complex and intriguing evolutionary pattern and functional diversity of mammalian ribonuclease than previously thought.
胰腺核糖核酸酶（RNASE1）是一种消化酶，一直是进化创新和功能多样化研究中的关键模型之一。人们认为RNASE1基因复制与前肠发酵食草动物的食草适应性相关。在此，我们以前所未有的规模，基于基因序列和组织表达分析，对具有简单消化系统且缺乏典型食草动物微生物消化的犬型亚目动物的RNASE1基因进行了表征。值得注意的是，研究结果产生了关于犬型亚目动物RNASE1基因进化和功能的新假设。在鼬超科家族中发现了四个独立的基因复制事件，包括浣熊科、小熊猫科、臭鼬科和鼬科，这推翻了先前关于鼬科特异性复制的假设，但支持了鼬超科复制假设。此外，我们的分析揭示了RNASE1基因拷贝在选择压力、pI值和组织表达模式方面存在显著差异，表明它们的生理功能存在差异。值得注意的是，表达分析在多个组织中检测到了一个RNASE1假基因的转录，这增加了假基因也是核糖核酸酶功能多样化过程中潜在来源的可能性。总之，目前的研究表明，哺乳动物核糖核酸酶的进化模式和功能多样性比以前认为的要复杂得多且更具趣味性。
