Identification of At4g32460 promoter activity during Arabidopsis thaliana development using pBDX::ER-GFP plants (Additional file 1: Figure S1C). A) GFP fluorescence in radicle tissue of a 48-h germinating seed. B) GFP fluorescence in radicle tissue of a 72-h germinating seed. C) GFP fluorescence in different cell types of meristematic and transition zones of primary roots from 4-day-old seedlings. D) GFP fluorescence in vascular tissue of maturation zone of primary roots of 22-day-old plants. E) GFP fluorescence in pericycle-differentiated cells that constitute primordium of lateral root emerging from maturation zone of primary roots of 22-day-old plants. F) GFP fluorescence in vascular tissue of fully expanded leaves. G) GFP fluorescence in anthers and petals of stage-6 flowers. H) GFP fluorescence in vascular tissue of stamen filaments, anthers, petals, and stigma of stage-12 flowers. Scale bars =50 μm in A and B, 15 μm in D, 100 μm in E and F, and 300 μm in C, G, H, and I. Images A, B, E, F, G, and H are projections of confocal Z-stacks. C and D are longitudinal sections.