Biology subjects

Courtier-Orgogozo, V.

Publications and source records attributed to Courtier-Orgogozo, V..

4 recordsLinked to original sources

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↗

bioRxiv2018

Correlated Evolution of two Sensory Organs via a Single Cis-Regulatory Nucleotide Change

Diverse traits often covary between species. The possibility that a single mutation could contribute to the evolution of several characters between species is rarely investigated as relatively few cases are dissected at the nucleotide level. Drosophila santomea has evolved additional sex comb sensory teeth on its legs and has lost two sensory bristles on its genitalia. We found that a single nucleotide substitution in an enhancer of the scute gene contributes to both changes. The mutation alters a binding site for the Hox protein Abdominal-B in the developing genitalia, leading to bristle loss, and for another factor in the developing leg, leading to bristle gain. Our study shows that morphological evolution between species can occur through a single nucleotide change affecting several sexually dimorphic traits.\n\nOne Sentence SummaryWe identify one nucleotide substitution in a gene regulatory region contributing to evolutionary change of two distinct organs.

evolutionary biology↗

bioRxiv2018

Robustness of bristle number to temperature and genetic background varies with bristle type and is regulated by miR-9a.

Robustness is the invariance of a given phenotype when faced with a given incoming genetic or environmental variation. Such essential property is being studied in a wide diversity of traits in many organisms but it is difficult to compare the results obtained on the robustness of different traits with each other given the differences that exist between traits in the way they are measured, in their genetic architecture and development. In this study, we assessed robustness of bristle number to incoming genetic and environmental variation for eight bristle types in the fruit fly Drosophila melanogaster, allowing for a straightforward comparison of the robustness observed between bristle types. We measured the response of bristle number mean and variance to changes in temperature and in the number of copies of two genes (scute and miR-9a) known to be involved in bristle development. Many combinations between the three factors were tested, thus allowing to test for the effect of each factor in different contexts for the two other factors - to which we refer herein as different backgrounds. We have found different responses between bristle types, suggesting that they present different levels of robustness to the factors tested. In addition, we have found that temperature and miR-9a affect more generally the variance of the traits rather than their means, thus fulfilling a criteria usually admitted to identify robustness factors.

genetics↗

bioRxiv2017

Predicting the genetic loci of past evolution

Repetitions in the mutations found to be responsible for independent evolution of similar phenotypes in various taxa have led some biologists to propose that for certain evolutionary changes the causal mutations are predictable. We examine here the nature of the predictions that have been made and their associated arguments. Predictions about the loci of past evolution are retrodictions, i.e. inferences about events that occurred in the past. They are not based on elaborate models and they derive mainly from the observation of repeated cases of genetic evolution. Predictions at the nucleotide level or at the gene level have a higher inference gain than those for broader categories of genetic changes such as cis-regulatory mutations.

genetics↗