摘要
酪氨酸酶是生物体黑色素合成的关键限速酶,黑色斑纹是瓯江彩鲤（Cyprinus carpio var.color）体色的主要特点之一。以瓯江彩鲤的5种体色选育系F5为材料,探讨酪氨酸酶基因5个外显子及其在不同体色间的变异特性和承受选择压力的敏感性。结果发现：酪氨酸酶基因外显子1和外显子5的核苷酸变异率最高,选择性位点最多,易承受到选择压力;5个外显子的非同义替换率（d_N）与同义替换率（d_S）的比值（ω值）均小于1（0.10-0.67）,表明它们均受到净化选择压力;不同体色瓯江彩鲤的酪氨酸酶基因也均受到净化选择压力（ω=0.12～0.23）。应用PAML软件中的M2a和M8两种模型检测显示：无黑斑体色瓯江彩鲤所受正向选择压力位点数高于有黑斑体色,但不存在显著差异（P〉0.05）;酪氨酸酶基因中的部分氨基酸位点较易受正向选择压力。研究结果表明：瓯江彩鲤酪氨酸酶基因较保守,主要受净化选择作用,当前的人工选育未对酪氨酸酶基因造成显著的选择压力。
Tyrosinase（ TYR） is a key and rate-limited enzyme in melanin synthesis pathway. Black spots are one of the main body color characteristics in Oujiang color common carp（ Cyprinus carpio var. color）. In this study,the total of the fifth generations of Oujiang color common carp（ F5） were used to observe the variation and selective pressure sensitivity of tyrosinase（ TYR） gene among the five exons in this gene and among the five body color patterns in this fish. The results showed： the nucleotide variation rate and the number of their positive selection sites in exon 1 and exon 5 were higher than those of the other three exons,indicating these two exons were more easily subjected to selective pressure. The ratios（ ω） of d_N/d_Sof the five exons were all less than 1（ 0. 10- 0. 67）,which demonstrated there was purifying selection conducted in tyrosinase gene.Similarly,the ratio（ ω = 0. 12- 0. 23） illustrated there was also purifying selection in the five body color patterns of Oujiang color common carp. The amino acid site analysis of selection pressure using the Codeml models（ M2 a and M8） in the software PAML indicated that there were more positive selection sites in the fish without black spots than the fish with black spots,although there was no significant difference（ P〉 0. 05）.Furthermore,some amino acid sites were also found with more easily positive selection than the other acids in tyrosinase gene. Generally,tyrosinase gene was conservative in evolutionary process and mainly subjected to purifying selection in Oujiang color common carp,and no significant selection pressure on this gene was found under artificial selection in this fish.
出处
《上海海洋大学学报》
CAS
CSCD
北大核心
2016年第3期329-336,共8页
Journal of Shanghai Ocean University
基金
国家自然科学基金(30907725
31372521)
上海市科学技术委员会项目(15391900800)
关键词
瓯江彩鲤
酪氨酸酶基因
选择压力
遗传变异
Cyprinus carpio var
color
tyrosinase gene
selection pressure
genetic variation
