Transcriptome analysis of female reproductive tissues of Anastrepha obliqua and molecular evolution of eggshell proteins in the fraterculus group

Abstract

The investigation of cDNA libraries has been an important tool for the identification of new genes in nonmodel species such as the fruit flies from the Anastrepha fraterculus group. In the present study, we constructed a cDNA library from the female reproductive tissues of Anastrepha obliqua aiming to identify genes with high evolutionary rates. We sequenced 2304 clones obtained from the female reproductive tissues of A. obliqua flies. The expressed sequence tags generated a total of 816 unigenes which were classified into different protein classes. Among these,we identified chorionic and vitelline protein genes as being among the most highly expressed. We used unigene sequences to amplify a set of chorionic and vitelline genes, involved in the formation of the eggshell,in species of the fraterculus group. Four chorionic genes and two vitelline genes showed evidence of positive selection along the Anastrepha and/or Tephritidae lineage. The signal of selection detected for Vm26Aa was possibly generated by a gene duplication event. The rapid evolutionary rates indicate that these genes could serve as important markers in population and evolutionary studies, not only for species of this group, but possibly also for other Diptera.

Evidence for Introgression Among Three Species of the Anastrepha fraterculus Group, a Radiating Species Complex of Fruit Flies

“…DNA was extracted from individual flies by a slight modification of the method described by Chomczynski and Sacchi (1987) in order to maintain exoskeletons intact for future morphological analyses. Genes were selected from a cDNA library of reproductive tissues of A. obliqua ( Gonçalves et al, 2013 ). For primer design ( Supplementary Table S2 ), sequences were aligned to other Diptera available online ( Supplementary Table S3 ) using the software ClustalW ( Thompson et al, 1994 ) implemented in BioEdit ( Hall, 1999 ) and the stability of their structures were checked using OligoAnalyzer 3.0.…”

“…Even though these studies have used data from a range of methods, including behavior, morphometrics, karyotype, isozymes, pheromone, cuticular hydrocarbons, mtDNA and reproductive studies, they lack a comprehensive sampling across the species’ range and fail to fully integrate molecular and phenotypic data, which complicates their use in species identification. An indication of the complex taxonomic questions in this genus is that single-gene molecular phylogenies based on mtDNA ( McPheron et al, 1999 ; Smith-Caldas et al, 2001 ) or nuclear genes ( Barr et al, 2005 ; Ruiz et al, 2007 ; Sarno et al, 2010 ; Gonçalves et al, 2013 ), and even using multiple genes ( Mengual et al, 2017 ) have failed to identify species-specific fixed differences among the most closely related taxa, leading some to propose a multidisciplinary approach ( Dias et al, 2016 ).…”

“…We took advantage of a recently developed cDNA library of reproductive female tissues of A. obliqua ( Gonçalves et al, 2013 ), to select a set of 20 genes to study the evolutionary relationships and demographic history among three of the most widespread Anastrepha species in Brazil ( Nascimento et al, 1993 ) using a multilocus analysis. For this, we integrated phylogenetic methods that account for ILS and introgression as well as compared several speciation models under an approximate Bayesian computation framework.…”

Evolution of egg coats: linking molecular biology and ecology

“…In invertebrates, the oocyte coat genes have been mainly studied in marine invertebrates, particularly sea urchin and abalone (reviewed in Vacquier & Swanson ), and a small number of insects (fruit flies, Jagadeeshan & Singh ; Gonçalves et al . ; lepidopterans, Carter et al . ; mosquitoes, Marinotti et al .…”

“…Moreover, as ZP domain proteins also function outside egg coats (Jovine et al 2005), the evolution of ZP genes is likely to be affected also by egg coat-independent processes (Wong & Wessel 2006). In invertebrates, the oocyte coat genes have been mainly studied in marine invertebrates, particularly sea urchin and abalone (reviewed in Vacquier & Swanson 2011), and a small number of insects (fruit flies, Jagadeeshan & Singh 2007;Gonc ßalves et al 2013;lepidopterans, Carter et al 2013;mosquitoes, Marinotti et al 2014). Drosophila and the silk moth (Bombus mori) are classical model systems for the developmental genetics of oocyte coats (reviewed in Papantonis et al 2015).…”