Intra- and interspecies comparison of rhodopsin expression in the retina of Drosophila

• Applicant: Dr. Jens Rister
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 207887987

The Drosophila retina consists of about 700 ommatidia (unit eyes) that contain different photoreceptor (PR) types. Colour vision is mediated by R7 PRs that express one of two UV-sensitive Rhodopsins (Rhs; Rh3 or Rh4), and the underlying R8 PRs that contain either the blue-sensitive Rh5 or the green-sensitive Rh6. R7 and R8 Rhs are coupled in two ommatidial subtypes which are stochastically distributed throughout the retina: In inbred lab stocks, 70% of ommatidia have Rh4 in R7 coupled with Rh6 in R8, while the remaining 30% express Rh3 in R7 and Rh5 in R8. Although the pattern of Rh distribution is quite variable amongst individual flies, the 30:70 ratio appears to be evolutionarily conserved. The stochastic arrangement of PRs is reminiscent of the distribution of cones in the human retina. Interestingly, the ratio of long- and medium-wavelength sensitive cones is variable between human individuals with a broad range of opsin distribution. This proposal offers to analyze the variability in wildtype fly stocks and to understand whether it is a result of a noisy mechanism that controls the stochastic choice or whether it responds to environmental or genetic factors. To address this, I will take advantage of a collection of available Drosophila melanogaster stocks and closely related Drosophila species that were recently derived from natural populations that were also fully sequenced. This will allow me to address two main questions: (1) How variable is the 30:70 ratio of Rhs in wildtype isolates of Drosophila melanogaster? (2) How conserved is this ratio in related species? This will reveal how robust the underlying mechanisms are that control the stochastic choice, the expression of Rhs and tight coupling between R7 and R8 Rhs. Additionally, this will show whether variants with impaired colour vision occur as they do in human. The polymorphisms causing variability will be identified using the extensive Drosophila toolkit as well as available sequence data.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Claude Desplan, Ph.D.