Figure 4.

Expression of Pdu-Gsx, Pdu-Xlox and Pdu-Cdx during larval development. (A-F) Pdu-Gsx is expressed in distinct cell clusters in the apical hemisphere (red arrowheads), and stomodeum (yellow arrowheads) that marks the anterior end of the future gut. Expression is also found in ventral neuroectoderm (E, white arrowheads). (G, H) Later, Pdu-Gsx marks specific cells (black arrowheads) in midgut (G) and posterior foregut (H). (I-K) Early Pdu-Xlox expression is confined to cells in the medial ventral plate (I, J; white arrowheads), where weak expression also persists to later stages (K). (L, M) In parallel, Pdu-Xlox transcripts appear inside the larvae (black arrowheads), marking distinct cell clusters in prospective midgut. Weak expression is also observed in bilateral lobes of the larval brain (red asterisks). (N-P) In trochophore larva (N), Pdu-Cdx is prominent in the proctodeal area (black asterisk); which subsequently (O, P), resolves into cells of the posterior midgut and hindgut (black arrowheads), and pygidial epidermis (black asterisks). For Pdu-Gsx, we also observe signal in the anterior foregut region (yellow asterisk in H), but we presently cannot rule out that this anterior signal results from probe trapping in the foregut cavity rather than being a further Pdu-Gsx expression domain. Orientation of panels: (A, C, E, I, N, O) ventral views, apical/anterior to the top; (B, D, F, J) apical views, ventral to the bottom; (G, H, K-M, P) ventral views, anterior to the left. Asterisks mark stomodeum/foregut cavity (yellow), ventral plate (white), head lobes (red) and proctodeum/pygidium (black), respectively.

Hui et al. BMC Biology 2009 7:43   doi:10.1186/1741-7007-7-43
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