Insect pickpocket (PPK) receptors mediate diverse functions, among them the detection of mechano- and chemo-sensory stimuli. Notwithstanding their relevance, studies on their evolution only focused on Drosophila. We have analyzed the genomes of 26 species of eight orders including holometabolous and hemimetabolous insects (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera), to characterize the evolution of this gene family. PPKs were detected in all genomes analyzed, with 578 genes distributed in seven subfamilies. According to our phylogeny, ppk17 is the most divergent member, composing the new subfamily VII. PPKs evolved under a gene birth-and-death model that generated lineage-specific expansions usually located in clusters, while purifying selection affected several orthogroups. Subfamily V was the largest, including a mosquito-specific expansion that can be considered a new target for pest control. PPKs present a high gene turnover generating considerable variation. On one hand, Musca domestica (59), Aedes albopictus (51), Culex quinquefasciatus (48), and Blattella germanica (41) presented the largest PPK repertoires. On the other hand, Pediculus humanus (only ppk17), bees, and ants (6–9) had the smallest PPK sets. A subset of prevalent PPKs was identified, indicating very conserved functions for these receptors. Finally, at least 20% of the sequences presented calmodulin-binding motifs, suggesting that these PPKs may amplify sensory responses similarly as proposed for Drosophila melanogaster ppk25. Overall, this work characterized the evolutionary history of these receptors revealing relevant unknown gene sequence features and clade-specific expansions.

中文翻译：

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昆虫 PPK 基因家族的进化

昆虫扒手 (PPK) 受体介导多种功能，其中包括检测机械和化学感觉刺激。尽管它们具有相关性，但对其进化的研究仅集中在果蝇上。我们分析了包括全代谢和半代谢昆虫在内的 26 个物种的基因组，包括全代谢和半代谢昆虫（Blattodea、Orthoptera、Hemiptera、Phthiraptera、Hymenoptera、Lepidoptera、Coleoptera 和 Diptera），以表征该基因家族的进化。在所有分析的基因组中均检测到 PPK，其中 578 个基因分布在 7 个亚科中。根据我们的系统发育，ppk17 是最分歧的成员，构成了新的亚科 VII。PPKs 在基因出生和死亡模型下进化，该模型产生通常位于簇中的谱系特异性扩展，而纯化选择影响了几个正交群。亚科 V 是最大的，包括可被视为害虫防治新目标的特定蚊子扩展。PPK 呈现出高基因周转率，产生相当大的变异。一方面，Musca domestica (59)、Aedes albopictus (51)、Culex quinquefasciatus (48) 和德国小蠊 (41) 展示了最大的 PPK 库。另一方面，Pediculus humanus（只有 ppk17）、蜜蜂和蚂蚁（6-9）具有最小的 PPK 集。鉴定了一个流行的 PPK 子集，表明这些受体的功能非常保守。最后，至少 20% 的序列呈现出钙调蛋白结合基序，这表明这些 PPK 可能会像对黑腹果蝇 ppk25 提出的那样放大感觉反应。全面的，