Dopazo, H. | Search bioRxiv

bioRxiv2021

Evolution of the insect PPK gene family

Insect Pickpocket (PPK) receptors mediate the detection of stimuli of diverse sensory modalities, therefore having a relevant role for environmental sounding. Notwithstanding their relevance, studies on their evolution are scarce. We have analyzed the genomes of 26 species belonging to 8 insect orders (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera) to identify their PPK repertoires and study the evolution of this gene family. PPKs were detected in all genomes analyzed, with a total of 578 genes identified that distributed in 7 subfamilies. Our phylogenetic analysis allowed clarifying that the ppk17 gene appears to be the most divergent family member, composing a new group designed as subfamily VII. According to our analysis, PPKs evolved under a birth-and-death model that generated lineage-specific expansions usually located in clusters and the effect of strong purifying selection was seen for several orthogroups. Subfamily V was the largest one, presenting half of all PPKs studied, including a mosquito-specific expansion that can be considered a new target for pest control. Consistently with their sensory role, PPKs present a high gene turnover that generated considerable variation in the size of insect repertoires: Musca domestica (59), Blattella germanica (41), Culex quinquefasciatus (48), and Aedes albopictus (51) presented the largest PPK repertoires, while Pediculus humanus (only ppk17), bees and ants (6-9) had the smallest ones. The expansions identified in M. domestica and Bl. germanica also show promise as specific targets for controlling these nuisance insects. Our phylogenetic analysis revealed a subset of prevalent PPKs across insect genomes, suggesting a very conserved function that resembles the case of antennal ionotropic receptors. Finally, we identified new highly conserved residues in the second transmembrane domain that may be key for receptor function. Besides, more than a hundred PPK sequences presented calmodulin binding motifs, suggesting that at least some members of this family may amplify sensory responses as previously proposed for D. melanogaster ppk25. Overall, our study is a first attempt to characterize the evolutionary history of this family of sensory receptors, revealing relevant unknown features and clade-specific expansions.

genomics↗

bioRxiv2020

Fine-scale genomic analyses of admixed individuals reveal unrecognized genetic ancestry components in Argentina

Similarly to other populations across the Americas, Argentinean populations trace back their genetic ancestry into African, European and Native American ancestors, reflecting a complex demographic history with multiple migration and admixture events in pre- and post-colonial times. However, little is known about the sub-continental origins of these three main ancestries. We present new high-throughput genotyping data for 87 admixed individuals across Argentina. This data was combined to previously published data for admixed individuals in the region and then compared to different reference panels specifically built to perform population structure analyses at a sub-continental level. Concerning the Native American ancestry, we could identify four Native American components segregating in modern Argentinean populations. Three of them are also found in modern South American populations and are specifically represented in Central Andes, Central Chile/Patagonia, and Subtropical and Tropical Forests geographic areas. The fourth component might be specific to the Central Western region of Argentina, and it is not well represented in any genomic data from the literature. As for the European and African ancestries, we confirmed previous results about origins from Southern Europe, Western and Central Western Africa, and we provide evidences for the presence of Northern European and Eastern African ancestries. Author SummaryThe human genetic diversity in Argentina reflects demographic processes during which the European colonists invaded a territory where Native American populations were settled. During the colonial period, the slave trade also prompted many African people to move to Argentina. Little is known about the origins of these three continental ancestry components in Argentinean populations nowadays. Genotyping data for 87 admixed individuals throughout Argentina was generated and data from the literature was re-analyzed to shed light on this question. We confirmed that most of the European genetic ancestry comes from the South, although several individuals are related to Northern Europeans. We confirmed that the African origins in Argentina mainly trace back from Western and Central/Western regions, and we document some proportion of Eastern African origins poorly described before. As for the Native American ancestry, we identified that it can be divided into four main components that correspond to Central Chile/Patagonia, Subtropical and Tropical Forests, Central Andes and Central Western region of Argentina. In order to understand the specificity of the genetic diversity in Argentina, more effort is required to generate specific massive genomic knowledge at the local level.

genetics↗