Figure 2. Identification of cis-Regulatory Changes in the Plate Size Interval.
(A) The freshwater allele of GDF6 is expressed at higher level than the marine allele in F1 hybrids. RNA was extracted from the indicated region of F1 hybrid fish from a cross between a small-plated freshwater (FW) and large-plated marine fish, and the relative abundance of the freshwater and marine alleles was quantified by pyrosequencing. Significance of observed deviation from the fraction of freshwater allele of 0.5 (dashed line) was tested using one sample t-test, and “*” represents p<0.05. Error bars represent SEM.
(B) Freshwater but not marine enhancer drives expression along the flanks of developing stickleback embryos. Marine and freshwater (FW) sequences were cloned from the regulatory region shown in Figure 1B into a GFP reporter vector with a minimal hsp70 promoter, and were then injected in fertilized one-cell stage embryos from marine fish. Pictures of the flanks of developing fry (dashed white lines) were taken at 4 dpf.
(C) Map of the enhancer region and sequences tested in transgenic fish. Repeating vertical lines represent regions of alignment between marine (red) and freshwater (blue) sequence, with gaps shown in the region of a complex repeat and a L2 LINE transposable element (TE) present in the freshwater but not marine sequence. Tall vertical lines denote the edges of the region added or removed from the modified constructs also tested for enhancer activity.