Figure 5.

ATHB5 correlates with EXPA3 promoter activity and GA-mediated growth specifically in the embryonic hypocotyl. Shown is relative increase in cell surface area (A to D) and increase in EXPA3 promoter activity (E–H) in wild-type, athb5-1 knockout, and 35S::GFP-ATHB5 embryos between the final germination stages (LTR to JG) on water (A and E) and on 5 µm PAC (B–D and F–H). A to D, Changes in cell surface area were determined as the ratio between LTR and JG and frequency normalized to enable comparisons across genotypes. E to H, Change in EXPA3 promoter activity between LTR and JG. The mean GUS quantity in each cell was calculated, and the difference between these means at JG and LTR was determined. All growth and reporter quantification data were derived from four embryos at each stage. White scale bar in D is 50 µm.