(a) A. thaliana flowers of ap1-12; gChAP1-GFP (ChAP1::ChAP1:GFP) genotype. (b) Beeswarm plot of average petal number (black) and average number of ectopic flowers (grey) in A. thaliana wild-type (n = 369 flowers, 15 plants), ap1-12 (n = 375 flowers, 15 plants) and ap1-12; gChAP1-GFP (n = 598 flowers, 25 plants, two independent insertion lines). Red lines indicate means. Levene’s test showed that the variance in petal number differed between wild-type and ap1-12 (***p=5.588e-05) and wild-type and ap1-12; gChAP1-GFP (**p=0.005823), but not between ap1-12 and ap1-−12; gChAP1-GFP (p=0.282). (c) Beeswarm plot of average petal number in A. thaliana ap1-12 plants either untransformed or transformed with chimeric AP1 constructs comprising the promoter sequences from either AtAP1 (A. thaliana) or ChAP1 (C. hirsuta) and the cDNA sequences from either AtAP1 or ChAP1. A two-way ANOVA test on ranked data showed a significant effect of promoter sequence on petal number (p=9.45e-08) but no effect of coding sequence (p=0.103) and no interaction effect between the promoter and coding sequences (p=0.258). Post-hoc Tukey's HSD tests showed that AP1 constructs containing the A. thaliana promoter had significantly higher petal number than those containing the C. hirsuta promoter, and all transgenic genotypes had higher petal number than ap1-12 at 0.05 level of significance. ap1-12: n = 375 flowers, 15 plants; ap1-12; pAtAP1::AtAP1: n = 1454 flowers, 37 plants, 10 independent insertion lines; ap1-12; pAtAP1::ChAP1: n = 1414 flowers, 36 plants, nine independent insertion lines; ap1-12; pChAP1::AtAP1: n = 986 flowers, 25 plants, five independent insertion lines; ap1-12; pChAP1::ChAP1: n = 717 flowers, 18 plants, five independent insertion lines. (d) Beeswarm plot of relative AP1 expression levels in inflorescences of C. hirsuta transgenic lines of gChAP1-GFP (black) and gAtAP1-GFP (orange) with 2 or four transgene copies. AP1 expression is quantified by qRT-PCR in three biological replicates of each sample and expressed relative to AP1 expression in wild-type inflorescences (dashed line). Relative AP1 expression is higher for gAtAP1-GFP lines, both for two (Student’s t-test, p<0.01) and four (p<0.05) transgene copies. n = 26 plants from six independent insertion lines for gAtAP1-GFP; n = 24 plants from five independent insertion lines for gChAP1-GFP. (e–f) Surface projections showing nuclear expression (green) of gAtAP1-GFP (d) and gChAP1-GFP (e) in stage 4 C. hirsuta flowers viewed from the lateral sepal. The dashed circle indicates the petal initiation domain on the floral meristem. (g) Boxplot of the size of inter-sepal regions (Physical) and the extent of AP1 expression along these transects into whorl 2 (AP1 expr) in C. hirsuta stage four floral meristems of gAtAP1-GFP and gChAP1-GFP. Size of the AP1 expression domain differs significantly between genotypes (Wilcoxon test, p<0.001; n = 7 samples each genotype) but physical size does not (p=0.44). Box and whiskers: quartiles, circles: outliers, black lines: median. Scale bars: 0.5 mm (a), 20 µm (e, f).