Cocca E, Ratnayake-Lecamwasam M, Parker S K, Camardella L, Ciaramella M, di Prisco G, Detrich H W
Istituto di Biochimica delle Proteine ed Enzimologia, Consiglio Nazionale delle Ricerche, Naples, Italy.
Proc Natl Acad Sci U S A. 1995 Mar 14;92(6):1817-21. doi: 10.1073/pnas.92.6.1817.
Alone among piscine taxa, the antarctic icefishes (family Channichthyidae, suborder Notothenioidei) have evolved compensatory adaptations that maintain normal metabolic functions in the absence of erythrocytes and the respiratory oxygen transporter hemoglobin. Although the uniquely "colorless" or "white" condition of the blood of icefishes has been recognized since the early 20th century, the status of globin genes in the icefish genomes has, surprisingly, remained unexplored. Using alpha- and beta-globin cDNAs from the antarctic rockcod Notothenia coriiceps (family Nototheniidae, suborder Notothenioidei), we have probed the genomes of three white-blooded icefishes and four red-blooded notothenioid relatives (three antarctic, one temperate) for globin-related DNA sequences. We detect specific, high-stringency hybridization of the alpha-globin probe to genomic DNAs of both white- and red-blooded species, whereas the beta-globin cDNA hybridizes only to the genomes of the red-blooded fishes. Our results suggest that icefishes retain inactive genomic remnants of alpha-globin genes but have lost, either through deletion or through rapid mutation, the gene that encodes beta-globin. We propose that the hemoglobinless phenotype of extant icefishes is the result of deletion of the single adult beta-globin locus prior to the diversification of the clade.
在鱼类分类群中，南极冰鱼（南极鱼科，南极鱼亚目）独树一帜，它们进化出了补偿性适应机制，能够在没有红细胞和呼吸氧转运蛋白血红蛋白的情况下维持正常的代谢功能。尽管自20世纪初以来人们就已经认识到冰鱼血液独特的“无色”或“白色”状态，但令人惊讶的是，冰鱼基因组中珠蛋白基因的情况仍未得到探索。我们利用南极岩鳕（南极鱼科，南极鱼亚目）的α-珠蛋白和β-珠蛋白cDNA，在三种白血冰鱼和四种红血南极鱼近亲（三种南极鱼，一种温带鱼）的基因组中探测与珠蛋白相关的DNA序列。我们检测到α-珠蛋白探针与白血和红血物种的基因组DNA都发生了特异性的高严谨度杂交，而β-珠蛋白cDNA仅与红血鱼类的基因组杂交。我们的结果表明，冰鱼保留了α-珠蛋白基因的无活性基因组残余，但通过缺失或快速突变失去了编码β-珠蛋白的基因。我们推测，现存冰鱼无血红蛋白的表型是在该进化枝多样化之前单个成年β-珠蛋白基因座缺失的结果。
