Fig. 4.

Dynamics and regulation of gap genes in Tribolium germband. (A) Gap genes continue to be expressed sequentially in the posterior end of WT Tribolium germband (the so-called growth zone); cad is expressed in the growth zone and retracts as the germband elongates. More to the anterior, early expressed gap gene domains stabilize and eventually fade. Expression patterns are tracked by dots. Faint dots represent decaying expression. Dots outlined in black signify the second expression domains of mlpt and gt. (B) In axn RNAi embryos, germband experiences very limited axial elongation, and cad expression does not retract. Nevertheless, gap genes continue to emanate from the posterior and propagate toward anterior until they reach the (much reduced in size) head lobes. Expression patterns are tracked by arrows. Arrows outlined in black signify the second domain of mlpt and gt. For detailed description of axn RNAi phenotype, see SI Detailed Description of Gap Gene Expression in WT and axn RNAi Embryos. For the full dataset of all gap gene expression dynamics during germband stage, see Fig. S3. In all embryos shown, anterior is to the left.