Université de Lyon, Institut de Génomique Fonctionnelle de Lyon, CNRS UMR 5242, École Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, France.
Howard Hughes Medical Institute and Laboratory of Molecular Biology, University of Wisconsin, Madison.
Genome Biol Evol. 2019 Jun 1;11(6):1541-1551. doi: 10.1093/gbe/evz094.
The birth-and-death evolutionary model proposes that some members of a multigene family are phylogenetically stable and persist as a single copy over time, whereas other members are phylogenetically unstable and undergo frequent duplication and loss. Functional studies suggest that stable genes are likely to encode essential functions, whereas rapidly evolving genes reflect phenotypic differences in traits that diverge rapidly among species. One such class of rapidly diverging traits are insect cuticular hydrocarbons (CHCs), which play dual roles in chemical communications as short-range recognition pheromones as well as protecting the insect from desiccation. Insect CHCs diverge rapidly between related species leading to ecological adaptation and/or reproductive isolation. Because the CHC and essential fatty acid biosynthetic pathways share common genes, we hypothesized that genes involved in the synthesis of CHCs would be evolutionary unstable, whereas those involved in fatty acid-associated essential functions would be evolutionary stable. To test this hypothesis, we investigated the evolutionary history of the fatty acyl-CoA reductases (FARs) gene family that encodes enzymes in CHC synthesis. We compiled a unique data set of 200 FAR proteins across 12 Drosophila species. We uncovered a broad diversity in FAR content which is generated by gene duplications, subsequent gene losses, and alternative splicing. We also show that FARs expressed in oenocytes and presumably involved in CHC synthesis are more unstable than FARs from other tissues. Taken together, our study provides empirical evidence that a comparative approach investigating the birth-and-death evolution of gene families can identify candidate genes involved in rapidly diverging traits between species.
诞生和灭绝进化模型提出，多基因家族的一些成员在系统发育上是稳定的，随着时间的推移，它们作为单个拷贝持续存在，而其他成员在系统发育上是不稳定的，经历频繁的复制和丢失。功能研究表明，稳定的基因可能编码基本功能，而快速进化的基因反映了在物种间迅速分化的特征上的表型差异。快速分化的特征之一是昆虫表皮碳氢化合物 (CHC)，它们在化学通讯中具有双重作用，既是短距离识别信息素，又是保护昆虫免受干燥的作用。昆虫 CHC 在相关物种之间迅速分化，导致生态适应和/或生殖隔离。由于 CHC 和必需脂肪酸生物合成途径共享共同的基因，我们假设参与 CHC 合成的基因是进化不稳定的，而那些与脂肪酸相关的必需功能相关的基因是进化稳定的。为了验证这一假设，我们研究了参与 CHC 合成的脂肪酸酰基辅酶 A 还原酶 (FAR) 基因家族的进化历史。我们在 12 种果蝇物种中编译了一个独特的 200 个 FAR 蛋白数据集。我们发现 FAR 含量的多样性很广，这是由基因复制、随后的基因丢失和选择性剪接产生的。我们还表明，在脂肪体细胞中表达的 FAR（可能参与 CHC 合成）比来自其他组织的 FAR 更不稳定。总之，我们的研究提供了经验证据，表明比较研究基因家族的诞生和灭绝进化可以识别参与物种间快速分化特征的候选基因。
