Distinct Functional Constraints Partition Sequence Conservation in a cis-Regulatory Element
(A) A schematic depiction of GABAergic neurons in C. elegans. (B) Expression pattern of C. elegans promoter unc-47::GFP in C. elegans. (C) Expression pattern of C. briggsae promoter unc-47::GFP in C. briggsae. Photographs of worms are composites of multiple exposures of the same individual that capture the full complement of D-type neurons, in all focal planes, expressing GFP. (D) Vista plot of primary sequence conservation in the promoter region of unc-47 from C. briggsae, C. remanei and C. brenneri aligned to C. elegans. Window size = 20 bp, threshold = 70%. (E) Schematic depiction of full-length and proximal promoters. Consistency of GFP expression in D-type neurons for full-length and proximal promoters from C. elegans (F) and C. briggsae (G). For both C. elegans and C. briggsae, the average number of cells expressing GFP is lower for the proximal promoter compared to full-length (Wilcoxon test, p = 3.2×10−3 and p = 3.4×10−8, respectively). (H) Distribution of ratios of GFP expression intensity in DVB relative to D-type neurons for the full-length and proximal promoters at 20°C. Each strain is represented by 100 animals. The two distributions are significantly different (Wilcoxon test, p = 1.8×10−5; Kolmogorov-Smironov test, p = 1.1×10−8).