Protein Domains Driving Hox Protein Function Figure 4. Protein domain mutations inducing neomorphic activities. A. Localized PS7 dpp expression (green) in the visceral mesoderm (in situ hybridization, white arrow) relies on posterior repression by AbdA (upper panels). Ubiquitous mesodermal (24B-Gal4 driven) expression of AbdA (red) represses dpp expression in PS7 (red arrow; middle panels) B. Localized PS8 expression of wg (green) in the visceral mesoderm (in situ hybridization, white arrow) relies on activation by AbdA. Ubiquitous AbdA in the mesoderm (24B-Gal4) induces anterior ectopic wg expression (red arrow; middle panels). In A and B, the effect of the AbdAHX,UA variant on dpp (A) or wg (B) expression is illustrated (lower panels). Right panels are magnifications of the boxed areas. Graphs (% of remaining activities compared to the wild type AbdA protein (WT) following domain mutations) using the boxplot representation on the right summarize quantitative analyses (see Text S1 and Figure S2 (dpp) and S3 (wg) for full illustration). A graded color-coded bar above the graphs illustrates the level of protein activity, ranging from light green (full activity) to black (no activity). Neomorphic activities, ie qualitative changes in protein activity, are depicted in red. doi:10.1371/journal.pgen.1002302.g004 arm-Gal4 driver, to repress Dll (Figure 7A and Figure S7) and Antp (Figure 7B and Figure S8) was evaluated by examining the activity of a Hox responsive Dll enhancer (DME, [44]) and the expression of the Antp protein, respectively (see Text S1). Single domain mutations do not strongly affect repressive activities of AbdA on Dll and Antp, leading to a mean loss of 40%, with the exception of the TD mutation, which affects more (60%) the repressive activities on Antp. Combining domain mutations leads to stronger effects: in the case of Dll, simultaneous mutation of the HX and UA domains almost completely abolishes AbdA repressive PLoS Genetics | www.plosgenetics.org 5 October 2011 | Volume 7 | Issue 10 | e1002302