Fig. 2. Tec29 embryos show delays in invagination of the salivary placodes. (A) Changes in the length of the salivary gland (µm) as the placode cells invaginate during stage 12 of embryogenesis and at stages 13 through 16. Progression through stage 12 was monitored by the position of the tip of the germ band (as percent embryo length measured from the posterior end of the embryo). The bars show the mean length of the salivary glands in embryos whose germ band tip lies in the indicated intervals. Seventy-five wild-type salivary glands and 46 Tec29^K00206 salivary glands from embryos at different stages were measured. As the germ band has finished retraction by the end of stage 12, the later stages are indicated only by stage numbers, not position. In w¹¹¹⁸ embryos (blue bars), the length of the salivary glands gradually increases during stage 12 and then decreases slightly at stages 13-16. In Tec29^K00206 embryos (red bars), there is no increase in length of gland observed at mid stage 12 (*); however, the length of the gland increases and exceeds w¹¹¹⁸ at stage 15 (**). (B) This graph shows the area of the salivary placodes on the surface measured in the same embryos used for measurement in A. Although there is a decrease in the surface area of the placodes in w¹¹¹⁸ embryos (blue bars), in Tec29^K00206 embryos (red bars) the area of the placodes does not decrease such that at stage 13-14, one-third of the placode is still on the surface. Uninvaginated cells remain on the surface of Tec29^K00206 embryos at stage 15-16; however, these cells have moved more anteriorly in the head and are hard to quantitate.