Poster  D23SY03PS1105

cis-regulatory evolution and functional diversification of gene duplicates in Diptera

Author(s): Tanaka K, Hazbun A, Vreede B, Diekmann Y, Roch F, Sucena É

Summary:

Gene duplication plays a major role in evolution of novel gene functions as it provides a material basis for variation and selection. We are interested in elucidating how cis-regulatory changes contribute to functional diversification ensuing gene duplication. To address this question we are studying the Three-Finger-Domain Protein/Ly6 gene family in insects. Members of this family encode different GPI-anchored membrane proteins and are fully conserved across drosophilids. Our analyses of the sequenced insect genomes indicate that a subset of these genes is unique to higher dipterans. We are focusing our attention on seven paralogues of Drosophila, which our phylogenetic analysis showed to derive from sequential duplications of a single orthologue. In order to determine how their expression domains diversified, we have characterized the embryonic expression patterns of the Drosophila paralogues and their unduplicated orthologues in other insects representing different phylogenetic positions and stages of duplication (the Mediterranean fruit fly, Ceratitis capitata, the scuttle fly, Megaselia abdita, the mosquito, Anopheles, the butterfly, Bicyclus anynana and the red flour beetle, Tribolium castaneum). We found that the original expression domain of the unduplicated orthologue localized predominantly to the developing nervous system, which, upon subsequent duplications, expanded to a wide array of tissues. While a subset of the duplicates retained the tissue-specificity of the unduplicated orthologues, the others acquired novel tissue-specific expression suggesting neofunctionalization. We are currently identifying the cis-regulatory elements of the duplicates and the unduplicated orthologues to elucidate the cis-regulatory mechanisms underlying the evolution of divergent expression patterns.