Distinct Functional Constraints Partition Sequence Conservation in a cis-Regulatory Element
Distribution of fluorescence intensity driven by C. elegans full-length (A) and proximal (B), and C. briggsae full-length (C) and proximal (D) promoters in C. elegans at two temperatures (red for 26°C and blue for 15°C). For each individual, the log intensity in D-type neurons is plotted against the log intensity in DVB. Individuals that did not show any fluorescence in DVB were excluded from analysis. Data for additional strains are given in Figure S4. Superimposed on each graph is a schematic of the construct used: a straight line represents C. elegans promoter of unc-47, a wavy line represents C. briggsae promoter of unc-47. The gray vertical bar indicates the 5′ boundary of the proximal promoter.