Evolution of male-biased genes in Drosophila

Recent work demonstrated that X-linked male-biased genes have two special characteristics: (i) underrepresentation an the X chromosome, (ii) lower conservation in comparison to A. gambiae. The evolutionary forces creating this pattern are completely unknown. This proposal aims to take advantage of the soon to be completed genomic sequence of D. pseudoobscura. Using expression profiling (cDNA arrays and realtime PCR) genes will be identified which are X-linked and malebiased in D. melanogaster, but not in D. pseudoobscura. The analysis of these genes in the phylogenetic framework of the melanogaster and obscura group will allow to pinpoint when the expression pattern of these genes changed. The ratio of non-synonymous to synonymous substitutions in these genes will be used to test whether the presumed functional shift (as indicated by a shift in expression pattern) was driven by directional selection. The second aspect of the proposal takes advantage of the different chromosomal organization of D. melanogaster and D. pseudoobscura. Muller`s element D corresponds to one autosomel chromosome arm in D. melanogaster, but forms part of the X chromosome in D. pseudoobscura. This difference permits to contrast the fate of male-biased genes, which were located an autosomes in D. melanogaster, but map to the X chromosome in D. pseudoobscura. lf similar evolutionary forces are operating in D. pseudoobscura, these male-biased genes should also be underrepresented an the D. pseudoobscura X chromosome.