Dynamics and function of intron sequences of thewinglessgene during the evolution of theDrosophilagenus

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Abstract
SummaryTo understand the function and evolution of genes with complex patterns of expression, such as theDrosophila winglessgene, it is essential to know how their transcription is regulated. However, extracting the relevant regulatory information from a genome is still a complex task. We used a combination of comparative genomics and functional approaches to identify putative regulatory sequences in two introns (1 and 3) of thewinglessgene and to infer their evolution. Comparison of the sequences obtained from severalDrosophilaspecies revealed colinear and well‐conserved sequence blocks in both introns.Drosophila willistonishowed a rate of evolution, in both introns, faster than expected from its phylogenetic position. Intron 3 appeared to be composed of two separate modules, one of them lost in the willistoni group. We tested whether sequence conservation in noncoding regions is a reliable indicator of regulatory function and, if this function is conserved, by analyzingD. melanogastertransgenic reporter lines harboring intron 3 sequences fromD. melanogaster(Sophophorasubgenus) and the species from theDrosophilasubgenus presenting the most divergent sequence,D. americana. The analysis indicated that intron 3 contains pupal enhancers conserved during the evolution of the genus, despite the fact that only 30% of theD. melanogasterintron 3 sequences lie in conserved blocks. Additional analysis ofD. melanogastertransgenic reporter lines harboring intron 3 sequences fromD. willistonirevealed the absence of an abdomen‐specific expression pattern, probably due to the above‐mentioned loss of a regulatory module in this species.