Evolution of the PPK gene family in insects

LATORRE-ESTIVALIS, JOSE MANUEL; DOPAZO, HERNÁN; ALMEIDA, FRANCISCA CUNHA; BARROZO, ROMINA B; PONTES, GINA; LORENZO, MARCELO GUSTAVO

Congreso; 6th Congress of the Latin American Association of Chemical Ecology; 2021

Universidad de Buenos Aires

Insect pickpocket (PPK) receptors mediate diverse functions, among them the detection of mechano- and chemo-sensory stimuli. These receptors are encoded by genes belonging a single gene family in insects. To have a better understanding of their evolution we searched for PPK genes in the genomes of 26 species of 8 orders including holometabolous and hemimetabolous insects (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera). Our searches found 578 PPK genes in total and at least one gene per species. Phylogenetic analyses support their classification into 7 subfamilies, of which, subfamily VII, represented by ppk17 in Drosophila melanogaster, was the most divergent. The PPK gene family evolved according to a gene birth-and-death model that generated lineage‐specific expansions, which were usually located in clusters in the genome. The different subfamilies had very different number of genes and evolutionary dynamics: some were more conserved across insect orders whereas other subfamilies had high turnover rates. Significant differences in repertoire were observed among species: on one hand, Musca domestica (59), Aedes albopictus (51), Culex quinquefasciatus (48), and Blattella germanica (41) presented the largest PPK repertoires and 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 twenty percent of the sequences presented calmodulin-binding motifs, suggesting that these PPKs may amplify sensory responses similarly as proposed for D. melanogaster ppk25. Overall, this work characterized the evolutionary history of these receptors revealing relevant unknown gene sequence features and clade-specific expansions.