Figure 4.

Organization of the honey bee Hox complex and expression of Hox genes. Illustration (not to scale) of Hox complexes from (A) D. melanogaster and (B) honey bee. Homeobox genes are shown as colored rectangles with arrows indicating the direction of transcription. Non-homeobox genes are shown as ovals, non-protein-coding genes as yellow circles. (B, i–x) In situ hybridization to honey bee embryos using Hox gene probes. Embryos are oriented with anterior up. Scale bars, 100 μm. (i and ii) Honey bee labial (lab) expression in a stage 10 embryo. lab is expressed in small, paired subsets of cells (asterisks) in the intercalary segment (magnified in ii). (iii and iv) Honey bee zen expression in a stage 3 embryo (iii, lateral view) and a stage 10 embryo (iv, ventral view). In early development, zen is expressed in the dorsal extraembryonic membranes. This persists until stage 9. Expression is then seen in cells of the CNS (iv). (v) Honey bee dfd expression in a stage 9 embryo (ventral view). Dfd is expressed in the mandibular and maxillary segments, especially in the limb buds. (vi and viii) Expression of honey bee ftz in stages 4 (vi and vii) and 5 (viii) (lateral views). Cells in a broad trunk domain express honey bee ftz. Expression in this domain fades, forming broad stripes (vii) at a spacing consistent with double segment periodicity (Osborne and Dearden 2005a). In viii, three broad stripes are visible (asterisks), but the embryo is damaged at the posterior end. (ix) Expression of honey bee Ultrabithorax (Ubx) RNA. Ubx is expressed in cells from A1 to A8. (x) Expression of honey bee abd-A RNA in a stage 10 embryo. abd-A is expressed in segments A2–A8 more broadly than Ubx. (xi) Expression of honey bee Abd-B RNA in a stage 9 embryo. Abd-B is expressed in segments A9–A10, but in later stages comes to be expressed in the posterior edges of A7 and A8 (data not shown).