Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes

Abstract

Background Tsetse flies ( Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans ( G. morsitans morsitans , G. pallidipes , G. austeni ), Palpalis ( G. palpalis , G. fuscipes ), and Fusca ( G. brevipalpis ) which represent different habitats, host preferences, and vectorial capacity. Results Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges. Conclusions Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies. Electronic supplementary material The online version of this article (10.1186/s13059-019-1768-2) contains supplementary material, which is available to authorized users.

Multi-level analysis of reproduction in the Antarctic midge,Belgica antarctica, identifies female and male accessory gland products that are altered by larval stress and impact progeny viability

“…The large proportion of apparently conserved, female-specific or female-enriched genes that are uncharacterized (≈44%) suggests there are many aspects of Belgica female physiology that remain poorly understood. However, the results of the GO analysis of the female-enriched gene set are consistent with results reported for Drosophila and other insect systems 36,[65][66][67] . In an analysis of genes differentially expressed between germline-naive and gonadectomized females in Drosophila, Parisi et al…”

“…Many of the male accessory gland genes from Belgica have orthologs based on predicted genes from midge and mosquito genomes, but few overlapping orthologs were identified that are expressed in the male accessory gland of B. antarctica compared to the male reproductive tissues of mosquitoes 25,26 . This is not surprising since a similar lack in orthology among male accessory gland products has been observed between Drosophila and Glossina and other higher flies 34,36 . We did not conduct biological examination of specific roles for accessory gland proteins from B. antarctica, such as whether their transfer during mating impacts refractoriness of females, as noted in many species 19,21,123,124 .…”

“…Between 60% and 71% of the reads from each RNA-seq set mapped to predicted genes. At the 4-fold or greater level for stage-specificity, overlap between the two methods was over 99%; thus we used the CLC Genomics (Qiagen) pipeline 36,58 for the remaining analyses (Table S1). When expression differences were compared among all developmental stages, each sex and associated reproductive organs were most similar, followed by similarity between adults, while the larval stages were the most unique ( Fig.…”

“…Even in Drosophila, the female accessory gland (paraovaria) remains one of the most understudied organs 128 . In tsetse flies, this organ provides nourishment to developing intrauterine larvae 22,36,129 , but there are no similarities, beyond standard housekeeping genes, between this organ in tsetse flies and B. antarctica. Of interest, regulation of transcript expression within the female accessory gland seems to be conserved 128 , suggesting that regulatory aspects may be similar but drive expression of specific genes related to unique functions of this organ in different flies.…”

“…Based on our results, one of the main functions of the gel is to provide a nutritional resource, which leads to a higher larval survival. Products of the accessory glands of females have been documented as food sources for insect species among many orders 22,36,53,132,133 . Production of gel substances surrounding eggs have been noted in other species, such as in stink bugs, where the gel serves as a source of nutrition, protects the eggs, and provides a vehicle to transfer microbial symbionts 53 .…”