Which of the following morphogens is essential for anterior-posterior patterning in Drosophila embryos?
Bicoid mRNA is localized anteriorly in Drosophila oocyte by swallow, exuperantia and staufen proteins anchoring to cytoskeleton. After fertilization, translation creates anterior-to-posterior protein gradient that functions as morphogen for anterior patterning. High anterior Bicoid activates hunchback, orthodenticle and buttonhead to specify head and thorax, while low posterior permits abdomen via repression of Caudal translation. Nuclear Bicoid concentration directly activates gap gene enhancers in threshold-dependent manner via homeodomain binding. Notch, FGF8 and retinoic acid do not provid
Ref: Nusslein-Volhard, Drosophila Development, Chapter 2: Bicoid Gradient and AP Patterning.
