Fig. 2.

Dynamics and regulation of gap genes in Tribolium blastoderm. (A–D) Gap genes are expressed as sequential waves in WT Tribolium embryos within cad expression domain; cad is expressed as a posterior-to-anterior gradient in the blastoderm (cad in A; quantification of the gradient is shown in B) and retracts to the posterior end (growth zone) of the embryo in the germband stage (23 h AEL onward). The hb, Kr, and mlpt waves are traced in blue, red, and green, respectively, in A. Extraembryonic expression of hb is marked with an asterisk. Head expression of mlpt (not considered in our analysis) is marked with a black dot. (C) Temporal profile of gap genes expression at the posterior end of WT embryo demonstrates their sequential (yet overlapping) expression. Color intensity of a bar within a time window reflects the percentage of embryos having a high level of gene expression of the corresponding gene in that time window (Materials and Methods). (D) Spatial distribution of gap genes along the AP axis of WT Tribolium blastoderm over time (Materials and Methods) demonstrates their posterior-to-anterior shifts over time. Dashed lines show expression domain borders ± SE. For detailed description of gap gene expression in WT, see SI Detailed Description of Gap Gene Expression in WT and axn RNAi Embryos. (E–H) The cad gradient is reduced and shifted toward posterior in lgs RNAi embryos. Correspondingly, gap gene waves are slower and shifted toward posterior. B and F are reproduced with permission from ref. 7. In all embryos shown, anterior is to the left.