Fig. 6. hb expression in the developing germband. Immunostaining and paired DAPI images show the development of S. americana hb domains as the posterior growth zone forms and begins extension. (A,B) At 44 hours hb is expressed throughout the embryo, but starts to become less intense in more posterior regions of the embryo (arrowhead). In addition, strong Hb labeling is seen at this time in extra-embryonic nuclei of the serosa (arrow). By around 48 hours (C,D), Hb protein has disappeared from the posterior growth zone, but remains expressed at low levels in the headlobes (diamond). At this time the transcript pattern (E,F) matches that of the protein. (G,H) As posterior growth begins, hb is absent from the posterior growth zone (arrowhead), but is upregulated in an arc anterior to it. Strong expression continues in serosal nuclei (arrows). By about 15% (I, closer view in J), there are at least four levels of hb expression: weak in the headlobes (diamond), strong anteriorly (arrow), weaker posteriorly (arrowhead) in the gnathal/thoracic domain and absent in the more posterior part of the embryo. These expression domains are still evident at 17% (K-N), for both the protein (K, closer view in L) and the transcript (M, closer view in N) in S. americana (K,L) and L. migratoria (M,N). Red lines in J,L,N indicate the boundary between the strong and weak hb domains. Anterior is at the top in all cases.
