Reverse Evolution in RH1 for Adaptation of Cichlids to Water Depth in Lake Tanganyika
Reverse Evolution in RH1 for Adaptation of Cichlids to Water Depth in Lake Tanganyika
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DOI：
10.1093/molbev/msq344
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发表时间：
2011-06-01
影响因子：
10.7
通讯作者：
Okada, Norihiro
中科院分区：
文献类型：
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作者：
Nagai, Haruka;Terai, Yohey;Okada, Norihiro
反向进化是生物学中的一种普遍现象，但逆转适应祖先状态的遗传变化的遗传机制尚不清楚。在这里，我们报告了第一个完全反向进化的两种氨基酸，丝氨酸和丙氨酸，在RH1视蛋白色素的单一位置，以适应水的深度。我们测定了坦噶尼喀湖四个部落不同栖息地深度的慈鱼的RH1序列。大多数种类可分为两类：浅水种RH1,292A种；深水种292S种。RH1色素的吸收光谱表明，这两种类型都适应了环境光环境。基于RH1基因座树和生态数据，我们推断了祖先氨基酸292位和每个部落祖先物种的深度范围(浅或深)的分布。根据这些估计，我们发现了两个明显的平行适应进化：从浅水到深水适应时，A292S替换至少发生了4次，而从深水适应到浅水适应时，相反的替换S292A发生了3次。后者代表了从起源状态到祖先状态的完全反向进化，随后是RH1色素功能逆转的适应性突变，并伴随着物种栖息地转移的逆转。
Reverse evolution is a widespread phenomenon in biology, but the genetic mechanism for the reversal of a genetic change for adaptation to the ancestral state is not known. Here, we report the first case of complete reverse evolution of two amino acids, serine and alanine, at a single position in RH1 opsin pigment for adaptation to water depth. We determined RH1 sequences of cichlid fishes from four tribes of Lake Tanganyika with different habitat depths. Most of the species were divided into two types: RH1 with 292A for species in shallow water or 292S for species in deep water. Both types were adapted to their ambient light environments as indicated by the absorption spectra of the RH1 pigments. Based on the RH1 locus tree and ecological data, we inferred the ancestral amino acids at position 292 and the distribution of the depth ranges (shallow or deep) of ancestral species of each tribe. According to these estimates, we identified two distinct parallel adaptive evolutions: The replacement A292S occurred at least four times for adaptation from shallow to deep water, and the opposite replacement S292A occurred three times for adaptation from deep to shallow water. The latter parallelism represents the complete reverse evolution from the derived to the ancestral state, following back adaptive mutation with reversal of the RH1 pigment function accompanied by reversal of the species habitat shift.