Fig. 2.

Family Relations II analysis of blimp1 locus and cis-regulatory reporter constructs. (A) Pairwise sequence analysis of two BAC sequences containing blimp1 genes, using the Family Relations II program. The horizontal line at the top represents the sequence of the Strongylocentrotus purpuratus BAC clone 163 O19; the ordinate represents Lytechinus variegatus BAC clone 060 B16. Red dots indicate 20-nucleotide stretches of sequence sharing ≥80% identity between the two species. Red boxes on the horizontal sequence indicate exons with the bent arrow showing the start of transcription in exon 1b of the Spblimp1 gene; numbered blue boxes indicate conserved regions. Conserved sequence patches are revealed by contiguous dots which produce short diagonal segments. (B) GFP reporter constructs for blimp1 cis-regulatory analysis. The top horizontal line represents the SpBlimp1b BAC-GFP recombinant in which the GFP gene has been inserted by homologous recombination at the site of the start of translation of the blimp1 gene, replacing exon1b. The various reporter constructs derived from the SpBlimp1b BAC-GFP recombinant are diagrammed below; construct names are at the left and the patterns of expression generated by these constructs at 18 hpf are indicated at the right. At this time the normal domain of blimp1 expression is the veg₂ endoderm. (C, D) Diagrams of mesenchyme blastula stage embryos displaying a normal endodermal domain of expression (blue) or ectopic ectodermal expression (red). (E) Representative fluorescent image of an 18 h embryo bearing construct 2, which is expressed ectopically. (F) Representative 18 h embryo displaying correct expression of the recombinant SpBlimp1b BAC-GFP. (G) Representative 18 h embryo bearing construct 34, which also generates a correct expression pattern.