Simpson-Brose M, Treisman J, Desplan C
Howard Hughes Medical Institute, Rockefeller University, New York, New York 10021-6399.
Cell. 1994 Sep 9;78(5):855-65. doi: 10.1016/s0092-8674(94)90622-x.
Anterior patterning of the Drosophila embryo is specified by the localized expression of the gap genes, which is controlled by the gradient of the maternal morphogen bicoid (bcd). Another maternal component, hunchback (hb), can substitute for bcd in the thorax and abdomen. Here we show that hb is required for bcd to execute all of its functions. Removal of both maternal and zygotic hb produces embryos with disrupted polarity that fail to express all known bcd target genes correctly. Proper expression of hb and the head gap genes requires synergistic activation by hb and bcd. We propose that it is the combined activity of bcd and hb, and not bcd alone, that forms the morphogenetic gradient that specifies polarity along the embryonic axis and patterns the embryo. bcd may be a newly acquired Drosophila gene, which is gradually replacing some of the functions performed by maternal hb in other species.
果蝇胚胎的前部模式由间隙基因的局部表达所决定，而间隙基因的表达受母体形态发生素双胸（bcd）梯度的控制。另一个母体成分驼背（hb），在胸部和腹部可以替代bcd。我们在此表明，hb是bcd执行其所有功能所必需的。去除母体和合子型hb会产生极性紊乱的胚胎，这些胚胎无法正确表达所有已知的bcd靶基因。hb和头部间隙基因的正确表达需要hb和bcd的协同激活。我们提出，形成沿胚胎轴确定极性并为胚胎定型的形态发生梯度的是bcd和hb的联合活性，而不只是bcd。bcd可能是一个新获得的果蝇基因，它正在逐渐取代其他物种中由母体hb执行的一些功能。
