Laboratório de Citogenética Evolutiva e Conservação Animal (LabCECA), Departamento de Genética, Universidade Federal do Paraná (UFPR), Paraná, Brazil.
J Mol Evol. 2023 Dec;91(6):793-805. doi: 10.1007/s00239-023-10135-y. Epub 2023 Oct 31.
Olfaction is a crucial capability for most vertebrates and is realized through olfactory receptors in the nasal cavity. The enormous diversity of olfactory receptors has been created by gene duplication, following a birth-and-death model of evolution. The olfactory receptor genes of the amphibians have received relatively little attention up to now, although recent studies have increased the number of species for which data are available. This study analyzed the diversity and chromosomal distribution of the OR genes of three anuran species (Engystomops pustulosus, Bufo bufo and Hymenochirus boettgeri). The OR genes were identified through searches for homologies, and sequence filtering and alignment using bioinformatic tools and scripts. A high diversity of OR genes was found in all three species, ranging from 917 in B. bufo to 1194 in H. boettgeri, and a total of 2076 OR genes in E. pustulosus. Six OR groups were recognized using an evolutionary gene tree analysis. While E. pustulosus has one of the highest numbers of genes of the gamma group (which detect airborne odorants) yet recorded in an anuran, B. bufo presented the smallest number of pseudogene sequences ever identified, with no pseudogenes in either the beta or epsilon groups. Although H. boettgeri shares many morphological adaptations for an aquatic lifestyle with Xenopus, and presented a similar number of genes related to the detection of water-soluble odorants, it had comparatively far fewer genes related to the detection of airborne odorants. This study is the first to describe the complete OR repertoire of the three study species and represents an important contribution to the understanding of the evolution and function of the sense of smell in vertebrates.
嗅觉是大多数脊椎动物的重要能力，是通过鼻腔中的嗅觉受体实现的。嗅觉受体的巨大多样性是通过基因复制产生的，遵循着一种诞生和死亡的进化模式。到目前为止，两栖动物的嗅觉受体基因受到的关注相对较少，尽管最近的研究增加了可供研究的物种数量。本研究分析了三种蛙类（非洲爪蟾、中华蟾蜍和波氏雨蛙）的 OR 基因的多样性和染色体分布。通过同源搜索、使用生物信息学工具和脚本进行序列过滤和比对，鉴定出了 OR 基因。在所有三种物种中都发现了高度多样化的 OR 基因，范围从 B. bufo 的 917 个到 H. boettgeri 的 1194 个，而 E. pustulosus 则有 2076 个 OR 基因。使用进化基因树分析识别了六个 OR 组。虽然 E. pustulosus 拥有记录在案的最多种类的 gamma 组基因（用于检测空气传播的气味），但 B. bufo 呈现出的假基因序列数量最少，beta 组和 epsilon 组都没有假基因。尽管 H. boettgeri 与非洲爪蟾共享许多适应水生生活方式的形态特征，并且与检测水溶性气味的相关基因数量相似，但它与检测空气传播气味的相关基因数量相比要少得多。本研究首次描述了这三种研究物种的完整 OR 基因库，为理解脊椎动物嗅觉的进化和功能做出了重要贡献。
