Comparison of the expression patterns of Sowah and Iroquois genes in amphioxus and fly. In situ hybridization of B. lanceolatum Sowah (A,B) and IrxB (C,D) genes in 15-h early neurulas (A,C) and 21-h neurulas (B,D) in dorsal and lateral views, respectively. Sowah transcripts were detected almost ubiquitously, with stronger expression in the dorsal half of the embryos. In contrast, IrxB showed a very defined and restricted pattern in the endoderm (en), notochord (nt), and neural plate (np). The anterior limit of expression in the neural plate, which is conserved in evolution (Irimia et al. 2010), is indicated by an arrow. The expression of IrxA and IrxC was similar at these stages (data not shown). (bp) Blastopore. In situ hybridization of sowah (E,F) and caup (G,H) in D. melanogaster stage 17 (E) and stage 12 (G) embryos (dorsal views) and third instar larvae wing imaginal discs (F,H, anterior is to the left). (E,F) sowah is expressed in the pharynx (*) and cephalic nervous system of late embryos (arrow in E points to nonspecific staining of the cuticular denticle belts), but is undetectable in the wing imaginal discs. (G,H) During embryonic development, ara and caup display coincident dynamic expression patterns in the epidermis (ep), central nervous system (CNS) and mesoderm, as well as in the head (h). In the wing disc, caup is expressed in the prospective regions of the 1, 3, and 5 longitudinal veins (L1, L3, L5), pleura (Pl); tegula (Tg); dorsal radius (DR); alula and lateral notum (n).
