Sat, 26 Jul 2008 13:37:56 BST CiteULike: emptyhbs trans_elements http://www.citeulike.org/user/emptyhb/tag/trans_elements CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/emptyhb/article/2609677 <i>Dev Biol (13 February 2008)</i><br /><br />The Bicoid morphogen evolved approximately 150 MYA from a Hox3 duplication and is only found in higher dipterans. A major difference between dipteran species, however, is the size of the embryo, which varies up to 5-fold. Although the expression of developmental factors scale with egg length, it remains unknown how this scaling is achieved. To test whether scaling is accounted for by the properties of Bicoid, we expressed eGFP fused to the coding region of bicoid from three dipteran species in transgenic Drosophila embryos using the Drosophila bicoid cis-regulatory and mRNA localization sequences. In such embryos, we find that Lucilia sericata and Calliphora vicina Bicoid produce gradients very similar to the endogenous Drosophila gradient and much shorter than what they would have produced in their own respective species. The common shape of the Drosophila, Lucilia and Calliphora Bicoid gradients appears to be a conserved feature of the Bicoid protein. Surprisingly, despite their similar distributions, we find that Bicoid from Lucilia and Calliphora do not rescue Drosophila bicoid mutants, suggesting that that Bicoid proteins have evolved species-specific functional amino acid differences. We also found that maternal expression and anteriorly localization of proteins other than Bcd does not necessarily give rise to a gradient; eGFP produced a uniform protein distribution. However, a shallow gradient was observed using eGFP-NLS, suggesting nuclear localization may be necessary but not sufficient for gradient formation. Shape and function of the Bicoid morphogen gradient in dipteran species with different sized embryos. Thomas Gregor Alistair Mcgregor Eric Wieschaus doi:10.1016/j.ydbio.2008.01.039 Dev Biol (13 February 2008) 2008-03-28T22:31:11-00:00 2008 Dev Biol 1095-564X binding_sites_turnover cis_regulatory_evolution drosophila trans_elements http://www.citeulike.org/user/emptyhb/article/2264102 <i>Mol Biol Evol, Vol. 15, No. 11. (November 1998), pp. 1403-1411.</i><br /><br />To study the microevolutionary processes shaping the evolution of the segmentation gene hunchback (hb) from Drosophila melanogaster, we cloned and sequenced the gene from 12 isofemale lines representing wild-type populations of D. melanogaster, as well as from the closely related species Drosophila sechellia, Drosophila orena, and Drosophila yakuba. We find a relatively low degree of sequence variation in D. melanogaster (theta = 0.0017), which is, however, consistent with its chromosomal location in a region of low recombination. Tests of neutrality do not reject a neutral-evolution model for the whole region. However, pairwise tests with different subregions indicate that there is a relative excess of polymorphic sites in the leader and the intron. Codon usage pattern analysis shows a particularly biased codon usage in the highly conserved regions, which is in line with the hypothesis that selection on translational accuracy is the driving force behind such a bias. A comparison of the expression pattern of hb in different sibling species of D. melanogaster reveals some regulatory changes in D. yakuba, which could be interpreted as changes in the timing of secondary expression domains. Microevolutionary divergence pattern of the segmentation gene hunchback in Drosophila. D Tautz L Nigro Mol Biol Evol, Vol. 15, No. 11. (November 1998), pp. 1403-1411. 2008-01-20T21:38:27-00:00 1998 Mol Biol Evol 0737-4038 15 11 1403 1411 drosophila pattern_formation species_divergence trans_elements