Comparative genomic analysis of teleost fish <Emphasis Type="Italic">bmal</Emphasis> genes |
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Authors: | Han Wang |
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Institution: | (1) Department of Zoology and Stephenson Research & Technology Center, University of Oklahoma, Norman, OK 73019, USA |
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Abstract: | Bmal1 (Brain and muscle ARNT
like 1) gene is a key circadian clock gene. Tetrapods also have the second Bmal gene, Bmal2. Fruit fly has only one bmal1/cycle gene. Interrogation of the five teleost fish genome sequences coupled with phylogenetic and splice site analyses found that
zebrafish have two bmal1 genes, bmal1a and bmal1b, and bmal2a; Japanese pufferfish (fugu), green spotted pufferfish (tetraodon) and Japanese medaka fish each have two bmal2 genes, bmal2a and bmal2b, and bmal1a; and three-spine stickleback have bmal1a and bmal2b. Syntenic analysis further indicated that zebrafish bmal1a/bmal1b, and fugu, tetraodon and medaka bmal2a/bmal2b are ancient duplicates. Although the dN/dS ratios of these four fish bmal duplicates are all <1, implicating they have been under purifying selection, the Tajima relative rate test showed that fugu,
tetraodon and medaka bmal2a/bmal2b have asymmetric evolutionary rates, suggesting that one of these duplicates have been subject to positive selection or relaxed
functional constraint. These results support the notion that teleost fish bmal genes were derived from the fish-specific genome duplication (FSGD), divergent resolution following the duplication led to
retaining different ancient bmal duplicates in different fishes, which could have shaped the evolution of the complex teleost fish timekeeping mechanisms.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Circadian clocks Conserved synteny Genome duplication Differential gene loss Ratio of nonsynonymous to synonymous substitutions and relative evolutionary rates |
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