Fig. 6. Model of Notch signalling controlling cell movement in the proventriculus. (A) Schematic illustration of the proventriculus primordium in late stage 13 (left) and stage 15 (right), highlighting the expression domains of proventriculus regulators and the cell movement events. Mesoderm in blue; ectoderm in orange; endoderm in green; ac, anterior boundary cells; pc, posterior boundary cells. Arrows highlight the inward movement of the ac. Note that the number of cells in the mesoderm-free region is about 10. For a better overview of the localisation of gene activities in the proventriculus primordium, only maximum gene activities are highlighted in the cells. The expression domains of regulators of proventricular development are shown in B. For further information, see text.