Lineage-specific expansions and contractions of the bitter taste receptor gene repertoire in vertebrates
Lineage-specific expansions and contractions of the bitter taste receptor gene repertoire in vertebrates
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DOI：
10.1093/molbev/msj106
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发表时间：
2006-05-01
影响因子：
10.7
通讯作者：
Go, Y
中科院分区：
文献类型：
--
作者：
Go, Y
苦味在生物体如何避免苦味有毒有害物质中起着至关重要的作用。先前的研究表明，人类有25个完整的苦味受体（T2R）基因，老鼠有34个。然而，由于最近的鸡基因组计划只报告了三个T2R基因，因此似乎在导致哺乳动物的谱系中发生了广泛的基因扩增，而在导致鸟类的谱系中发生了广泛的基因收缩。在这里，我检查了胎盘哺乳动物（狗，家犬，牛），有袋动物（负鼠，家鼠），两栖动物（青蛙，热带爪蟾）和鱼类（斑马鱼，斑马鱼，河豚，红鳉）的T2R基因库，以研究T2R基因在脊椎动物进化过程中的生与死过程。我表明：(1)第一次广泛的基因扩增发生在哺乳动物与爬行动物/鸟类分化之前，但在羊膜动物（爬行动物/鸟类/哺乳动物）与两栖动物分化之后；(2)随后的基因扩增持续发生在哺乳动物祖先谱系和导致两栖动物的谱系中，狗、牛、负鼠和青蛙的基因组中分别存在15、18、26和49个完整的T2R基因。(3)基因库的收缩发生在导致鸡的谱系中。因此，持续的基因扩增形成了哺乳动物的T2R库，但第一轮扩增后的收缩使鸡的T2R库缩小。这些剧目大小的戏剧性变化可能反映了每天从外部环境中摄取食物作为进化的驱动力。
The sense of bitter taste plays a critical role in how organisms avoid generally bitter toxic and harmful substances. Previous studies revealed that there were 25 intact bitter taste receptor (T2R) genes in humans and 34 in mice. However, because the recent chicken genome project reported only three T2R genes, it appears that extensive gene expansions occurred in the lineage leading to mammals or extensive gene contractions occurred in the lineage leading to birds. Here, I examined the T2R gene repertoire in placental mammals (dogs, Canis familiaris; and cows, Bos taurus), marsupials (opossums, Monodelphis domestica), amphibians (frogs, Xenopus tropicalis), and fishes (zebrafishes, Danio rerio; and pufferfishes, Takifugu rubripes) to investigate the birth-and-death process of T2R genes throughout vertebrate evolution. I show that (1) the first extensive gene expansions occurred before the divergence of mammals from reptiles/birds but after the divergence of amniotes (reptiles/birds/mammals) from amphibians, (2) subsequent gene expansions continuously took place in the ancestral mammalian lineage and the lineage leading to amphibians, as evidenced by the presence of 15, 18, 26, and 49 intact T2R genes in the dog, cow, opossum, and frog genome, respectively, and (3) contractions of the gene repertoire happened in the lineage leading to chickens. Thus, continuous gene expansions have shaped the T2R repertoire in mammals, but the contractions subsequent to the first round of expansions have made the chicken T2R repertoire narrow. These dramatic changes in the repertoire size might reflect the daily intake of foods from an external environment as a driving force of evolution.