Institut Jacques Monod

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Research projects

Our goal is to understand how and why specific phenotypes arise during evolution. We use all the available approaches (genomics, developmental biology, biochemistry, behavioral assays, genetics, etc.) to tackle the problem.

Ecological specialization to an obligatory host plant due to mutations in an enzyme gene

http://www.biology.ed.ac.uk/research/groups/jdeacon/

  Drosophila pachea is one of the rare insect species that is unable to metabolise cholesterol. It lives exclusively on one host plant, the senita cactus, and it requires 7-dehydrogenated sterols produced by this cactus to survive. We identified several coding mutations in an enzyme gene that have made D. pachea dependent on its host cactus. Our work suggests that these mutations are beneficial for D. pachea and have been subject to positive selection.
  Drosophila pachea has also evolved a resistance towards the toxic compounds of its host cactus. We would like to investigate the genetic basis of this resistance.

  We also plan to study how a moth species adapted to the senita cactus.



Evolution of left-right size asymmetry

  How left-right asymmetries in organ size develop remains a mystery. Drosophila pachea has evolved a unique left-right asymmetry in genitalia lobes. No left-right size asymmetry has been described in D. melanogaster. We are trying to uncover the mechanisms that triger asymmetric lobe development and the role of these asymmetric lobes during copulation. We use a stock of Drosophila pachea containing spontaneous symmetric mutant males and we perform micro-scale laser removal of lobe bristles and micro-scale surgery of lobes. We are also examining left-right asymmetries in behavior and morphology in species closely related to D. pachea, in order to understand how left-right asymmetry in lobe size evolved in D. pachea.








Evolution of a new stable phenotype





santomea bristles

  How robust phenotypes evolve despite developmental noise remains unclear. Does evolution of a new phenotype goes through an intermediate unstable state that is then stabilized due to fixation of additional mutations? Or does it evolve directly as a new phenotype that is stable across various external conditions? We are examining the evolution of a new genital sensory organ pattern in Drosophila santomea and aim to better characterize the molecular mechanisms that stabilize this recently evolved phenotype. Our goal is three-fold: (1) characterize and compare the development of these structures in D. santomea and its closely-related species, (2) identify the underlying genes and mutations that act collectively to produce a robust phenotype in pure species, and (3) unveil the selective forces at play on this evolved phenotype.



Evolution of genitalia lobe shape


  We wish to understand how diverse biological forms develop and evolve. To try to understand how genes and cellular mechanisms modulate organ shape in a subtle and precise way, we are examining the precise changes in genitalia lobe shape that have appeared during evolution in Drosophila melanogaster and its three closely related species. We would like to identify genes and mutations responsible for specific changes in lobe shape and to characterize in detail the development of the posterior lobe at the cellular level in D. melanogaster, in its closely related species, and in hybrid lines that carry a small piece of another species genome.