Da Lage, J.-L. | Search bioRxiv

bioRxiv2018

Evolution of salivary glue genes in Drosophila species

BackgroundAt the very end of the larval stage Drosophila expectorate a glue secreted by their salivary glands to attach themselves to a substrate while pupariating. The glue is a mixture of apparently unrelated proteins, some of which are highly glycosylated and possess internal repeats. Because species adhere to distinct substrates (i.e. leaves, wood, rotten fruits), glue genes are expected to evolve rapidly.\n\nResultsWe used available genome sequences and PCR-sequencing of regions of interest to investigate the glue genes in 20 Drosophila species. We discovered a new gene in addition to the seven glue genes annotated in D. melanogaster. We also identified a phase 1 intron at a conserved position present in five of the eight glue genes of D. melanogaster, suggesting a common origin for those glue genes. A slightly significant rate of gene turnover was inferred. Both the number of repeats and the repeat sequence were found to diverge rapidly, even between closely related species. We also detected high repeat number variation at the intrapopulation level in D. melanogaster.\n\nConclusionMost conspicuous signs of accelerated evolution are found in the repeat regions of several glue genes.

evolutionary biology↗

bioRxiv2017

The use of salivary α-amylase as an evolutionary solution to host selection in parasitoids

Foraging parasitoids use chemical signals in host recognition and selection processes. Thereby, chemicals from the herbivore hosts play a crucial role. When different herbivores are present in the same plant or field, the perception of specific volatiles and contact compounds emitted from the host itself enable the parasitoids both to differentiate between hosts and non-hosts and to estimate the health status of its host. During the host feeding process, contact between the parasitoid and its host is very crucial, and oral secretions from the host play a key role during the first contact for such evaluation by the parasitoid. Using an integration of behavioral observations, biochemical and sensory physiological approaches we demonstrate that female parasitoids of Cotesia flavipes recognize their host and oviposit in reaction to an -amylase, which is present in the oral secretions of the larvae of their host, Chilo partellus. This activity was also mediated by a purified -amylase synthetized from Drosophila melanogaster. Using this synthetized enzyme, we further demonstrate that the conformation of the enzyme rather than its catalytic site is responsible for this activity. This enzyme is activating gustatory neurons of the terminal antennal sensilla chaetica of C. flavipes females. -amylases are therefore good candidates for an evolutionary solution to host selection in parasitoids, thus opening new avenues for investigations in hosts-parasitoids interactions.

evolutionary biology↗