ALT Models of gap gene regulation and spatiotemporal dynamics of gap gene expression in WT Tribolium embryos. (C,D) HCR FISH detecting subsets of the four core gap genes (hb, Kr, mlpt, gt) in staged WT embryos (14-38 h AEL). Panel C shows expression of hb, Kr, and mlpt concurrently in the same embryos, while panel D shows mlpt and gt concurrently in the same embryos. All embryos are oriented with anterior to the left and posterior to the right.