Fig. 3. Prd expression overlaps with the pre-CF domain and paired is required for the pre-CF domain to form. Cross-section (A) and surface view (B) through a very early cycle 14 embryo showing Myosin (green) and the early single stripe expression of Prd (red). Optical sections from basal side of yolk stalks (C), through yolk stalks (D) and apical side of yolk stalks (E) showing overlap of first stripe of Prd expression (green) with pre-CF domain (deeper band of cellularization front as marked by Myosin in red). A lateral part of embryo (D) has had the green channel removed so the smaller yolk stalks of the pre-CF domain can be seen. (F,G) Representative example of prd/+ embryo (F, classified as 3.5 on 0-5 scale), and its homozygous prd sibling (G, classification of 1.0) stained with Myosin (green) and Neurotactin (a general cell surface marker in red). Embryos were also stained against Prd in far-red channel for genotyping purposes (not shown). (F,G) Embryos are a composite of a cross-section focal plane with the furrow canal focal plane super-imposed. The thin strips in the third row are higher magnifications of yolk stalks from the anterior domain (ad), pre-CF domain (pcf) and posterior domain (pd). The remaining inhomogeneity in the region of the pre-CF domain in G may reflect the role of additional AP patterning genes in the specification of this domain. The graph shows the results of a blind scoring of the pre-CF domain in prd/+ and prd– homozygous embryos. The data illustrates that although a minority of prd heterozygotes possess a poor pre-CF domain, no prd– homozygotes form a normal pre-CF domain (a rating of 3.5 or higher).
