Fig. 3. Line-specific regulatory modules responsible for regulating Hr-Otx transcription during cleavage stage. (A) Schematic representation of the regions, 5402-1473 bp and 812-24 bp. For analysis of their transcriptional activity, regions lacking the putative endogenous Hr-Otx promoter were placed upstream of the HrMA4a basal promoter. Dark gray lines indicate the region that exhibited lacZ transcription in Hr-Otx-expressing cells. The positions of the line-specific transcription regulatory modules (#1-#6) are indicated at the bottom. The regions marked by light gray lines directed lacZ transcription only weakly during cleavage stage. (B-G') Transcription of lacZ in 64-cell stage embryos injected with reporter constructs harboring regulatory modules #1 (B,B'), #2 (C,C'), #3 (D,D'), #4 (E,E'), #5 (F,F') and #6 (G,G'), as visualized by whole-mount in situ hybridization. Animal (B-G) and vegetal (B'-G') views are shown. The identity of the lacZ-transcribing cell line is indicated below the in situ hybridization specimens. Asterisk indicates that module #6 also drives lacZ transcription in all a-line cells from the 110-cell stage onward. (H) Frequency of lacZ-positive cells for a given cell line in 64-cell embryos injected with constructs harboring modules #1-#6. For color codes see Fig. 1