Fig. 1. Expression of Drosophila hb during embryogenesis. Immunostaining reveals the dynamic expression of Hb during D. melanogaster development, and provides a basis for interpretation of the grasshopper expression pattern. (A) At blastoderm stage, Hb is found in a large anterior domain (arrow) and a posterior domain around PS 13/14 (arrowhead). In a stage 12 germ band extended embryo (B), Hb is found in multiple tissues including the nervous system (arrow). In addition, it is expressed in extra-embryonic tissue and in nuclei around the yolk (arrowhead). Both domains are also seen in stage 13 germ band retracted embryos (C,D; arrow is neural expression, arrowhead is extra-embryonic expression), with the extra-embryonic domain shown in both a lateral (C) and dorsal view (D). Drosophila hb expression in a dissected stage 14 embryo (E) reveals a ‘bow-tie’-like pattern in each neuromere (arrow points to CNS) as well as in lateral domains (orange arrowheads) of mesodermal and possibly PNS expression. (F) Close-up view showing hb expression in the stage 15 CNS (arrow indicates the midline).