Newfeld S J, Gelbart W M
Biological Laboratories, Harvard University, Cambridge, MA 02138, USA.
J Mol Evol. 1995 Aug;41(2):155-60. doi: 10.1007/BF00170667.
Intercellular signaling molecules of the transforming growth factor-beta (TGF-beta) superfamily are required for pattern formation in many multicellular organisms. The decapentaplegic (dpp) gene of Drosophila melanogaster has several developmental roles. To improve our understanding of the evolutionary diversification of this large family we identified dpp in the grasshopper Schistocerca americana. S. americana diverged from D. melanogaster approximately 350 million years ago, utilizes a distinct developmental program, and has a 60-fold-larger genome than D. melanogaster. Our analyses indicate a single dpp locus in D. melanogaster and S. americana, suggesting that dpp copy number does not correlate with increasing genome size. Another TGF-beta superfamily member, the D. melanogaster gene 60A, is also present in only one copy in each species. Comparison of homologous sequences from D. melanogaster, S. americana, and H. sapiens, representing roughly 900 million years of evolutionary distance, reveals significant constraint on sequence divergence for both dpp and 60A. In the signaling portion of the dpp protein, the amino acid identity between these species exceeds 74%. Our results for the TGF-beta superfamily are consistent with current hypotheses describing gene duplication and diversification as a frequent response to high levels of selective pressure on individual family members.
转化生长因子-β（TGF-β）超家族的细胞间信号分子在许多多细胞生物的模式形成中是必需的。果蝇的“截瘫”（dpp）基因具有多种发育作用。为了增进我们对这个大家族进化多样化的理解，我们在美洲沙漠蝗中鉴定出了dpp。美洲沙漠蝗大约在3.5亿年前与果蝇分化，采用独特的发育程序，并且其基因组比果蝇大60倍。我们的分析表明，果蝇和美洲沙漠蝗中都只有一个dpp基因座，这表明dpp的拷贝数与基因组大小的增加无关。另一个TGF-β超家族成员，果蝇的60A基因，在每个物种中也只有一个拷贝。对果蝇、美洲沙漠蝗和人类的同源序列进行比较，这三个物种大约有9亿年的进化距离，结果显示dpp和60A的序列分歧都受到显著限制。在dpp蛋白的信号传导部分，这些物种之间的氨基酸同一性超过74%。我们对TGF-β超家族的研究结果与当前的假说一致，该假说认为基因复制和多样化是对单个家族成员高水平选择压力的常见反应。
