Genomic and karyotypic variation in Drosophila parasitoids (Hymenoptera, Cynipoidea, Figitidae)

Abstract

Drosophila melanogaster Meigen, 1830 has served as a model insect for over a century. Sequencing of the 11 additional Drosophila Fallen, 1823 species marks substantial progress in comparative genomics of this genus. By comparison, practically nothing is known about the genome size or genome sequences of parasitic wasps of Drosophila. Here, we present the first comparative analysis of genome size and karyotype structures of Drosophila parasitoids of the Leptopilina Förster, 1869 and Ganaspis Förster, 1869 species. The gametic genome size of Ganaspis xanthopoda (Ashmead, 1896) is larger than those of the three Leptopilina species studied. The genome sizes of all parasitic wasps studied here are also larger than those known for all Drosophila species. Surprisingly, genome sizes of these Drosophila parasitoids exceed the average value known for all previously studied Hymenoptera. The haploid chromosome number of both Leptopilina heterotoma (Thomson, 1862) and Leptopilina victoriae Nordlander, 1980 is ten. A chromosomal fusion appears to have produced a distinct karyotype for Leptopilina boulardi (Barbotin, Carton et Keiner-Pillault, 1979)(n = 9), whose genome size is smaller than that of wasps of the Leptopilina heterotoma clade. Like Leptopilina boulardi, the haploid chromosome number for Ganaspis xanthopoda is also nine. Our studies reveal a positive, but non linear, correlation between the genome size and total chromosome length in Drosophila parasitoids. These Drosophila parasitoids differ widely in their host range, and utilize different infection strategies to overcome host defense. Their comparative genomics, in relation to their exceptionally well-characterized hosts, will prove to be valuable for understanding the molecular basis of the host-parasite arms race and how such mechanisms shape the genetic structures of insectcommunities.

Chromosomes of Belonocnema treatae Mayr, 1881 (Hymenoptera, Cynipidae)

“…Furthermore, the latter karyotypes belong to a particular species complex where cryptic species were discovered (Abe 1998). Interestingly, similar chromosome numbers, n = 10 and 9, are characteristic of five studied species of another cynipoid family, Figitidae, in which two other species with n = 11 and 5 were also found (Gokhman 2009, Gokhman et al 2011). …”

Variation in genome size and karyotype among closely related aphid parasitoids (Hymenoptera, Aphelinidae)

“…This also applies to some genera of parasitoids, e.g. Leptopilina Förster, 1869 (Figitidae) with genome sizes ranging from 363 to 520 Mb (Gokhman et al 2011).…”

Partial venom gland transcriptome of a Drosophila parasitoid wasp, Leptopilina heterotoma, reveals novel and shared bioactive profiles with stinging Hymenoptera

“…The cDNA clones and sequences reported here can be used to examine specific gene expression patterns, to develop physical maps of the wasp genome (Gokhman, 2011), and to confirm DNA assemblies derived from deep sequencing methods. Drosophila genetics will facilitate the analysis of specific Lh venom proteins with potential effects on host physiology in vivo .…”