Relative quantitative gene expression in dissected flower tissues. TB1a expression is significantly stronger in ventral versus dorsal tepals of C. communis and C. dianthifolia but not T. pallida, and is expressed asymmetrically in different directions in stamens of all three species (top panel). TB1b expression is low or absent in floral tissues, but is expressed strongly in leaves (second top panel). GLO expression is significantly stronger in staminodes versus stamens of C. dianthifolia and C. communis, and is low to undetectable in outer tepals and gynoecia (second bottom panel). DEF expression is significantly stronger in dorsal versus ventral inner tepals of C. communis, being undetectable in the latter (bottom panel). β-ACT and EF1a were used as internal controls. Experiments were conducted with three to four technical replicates. Bars show mean and standard deviation. Second biological replicates were analyzed separately and are shown in Additional file 2. White bars, whole organs; blacks bars, dorsal organs; gray bars, ventral organs. Asterisks denote significant differences between dorsal and ventral organ comparisons. nd, not detected.