The two toothed jaws of cichlid fishes provide textbook examples of convergent evolution. Tooth phenotypes such as enlarged molar-like teeth used to process hard-shelled mollusks have evolved numerous times independently during cichlid diversification. Although the ecological benefit of molar-like teeth to crush prey is known, it is unclear whether the same molecular mechanisms underlie these convergent traits. To identify genes involved in the evolution and development of enlarged cichlid teeth, we performed RNA-seq on the serially homologous-toothed oral and pharyngeal jaws as well as the fourth toothless gill arch of Astatoreochromis alluaudi. We identified 27 genes that are highly upregulated on both tooth-bearing jaws compared with the toothless gill arch. Most of these genes have never been reported to play a role in tooth formation. Two of these genes (unk, rpfA) are not found in other vertebrate genomes but are present in all cichlid genomes. They also cluster genomically with two other highly expressed tooth genes (odam, scpp5) that exhibit conserved expression during vertebrate odontogenesis. Unk and rpfA were confirmed via in situ hybridization to be expressed in developing teeth of Astatotilapia burtoni. We then examined expression of the cluster’s four genes in six evolutionarily independent and phylogenetically disparate cichlid species pairs each with a large- and a small-toothed species. Odam and unk commonly and scpp5 and rpfA always showed higher expression in larger toothed cichlid jaws. Convergent trophic adaptations across cichlid diversity are associated with the repeated developmental deployment of this genomic cluster containing conserved and novel cichlid-specific genes.

中文翻译：

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包含新的和保守的基因的基因组簇与慈鲷的牙齿发育趋同有关。

慈鲷鱼的两个有齿的下颚提供了趋同进化的教科书例子。牙齿表型，例如用于加工硬壳软体动物的增大的臼齿状牙齿，在慈鲷多样化过程中独立进化了无数次。尽管已知臼齿压碎猎物的生态效益，但尚不清楚这些收敛特征是否具有相同的分子机制。为了鉴定参与增大的慈鲷牙齿进化和发育的基因，我们对Astatoreochromis alluaudi的连续同源牙齿的口腔和咽颌以及第四个无牙鳃弓进行了RNA-seq. 与无牙鳃弓相比，我们确定了 27 个在两个带牙颌骨上高度上调的基因。大多数这些基因从未被报道在牙齿形成中起作用。其中两个基因（unk、rpfA）在其他脊椎动物基因组中未发现，但存在于所有慈鲷基因组中。它们还与另外两个高度表达的牙齿基因（odam、scpp5）在基因组上聚类，这些基因在脊椎动物牙形成过程中表现出保守的表达。Unk和rpfA通过原位杂交证实在Astatotilapia burtoni 的发育牙齿中表达. 然后，我们检查了集群的四个基因在六个进化独立且系统发育不同的慈鲷物种对中的表达，每个物种对都有一个大齿和小齿物种。Odam和unk通常以及scpp5和rpfA在较大的齿慈鲷颌骨中总是表现出更高的表达。跨越慈鲷多样性的趋同营养适应性与这个包含保守和新颖慈鲷特异性基因的基因组簇的重复发育部署有关。