Fig. 2. GL2 gene expression in the root and hypocotyl of 3-day-old plants bearing the GL2::GUS or GL2::GFP reporter constructs. Postembryonic expression of GL2::GUS (blue staining) and GL2::GFP (green fluorescence) occurs preferentially in epidermal cells located outside periclinal cortical cell walls. Propidium iodide staining (red) was performed on plants in D and E to visualize cell boundaries. (A) Hypocotyl bearing the GL2::GUS transgene, stained for GUS activity (blue). Bar, 100 µm for A and B. (B) Hypocotyl bearing the GL2::GFP transgene, viewed by fluorescence microscopy (green). (C) Surface view of root tip from seedling with the GL2::GUS transgene, stained for GUS activity. Bar, 50 µm for C and D. (D) Surface view of root tip from seedling with GL2::GFP, viewed by fluorescence microscopy. The inset shows the arrangement of the underlying cortical cells, with an arrow marking the anticlinal cortical cell wall. (E) Median longitudinal optical section of root tip with the GL2::GFP transgene, viewed by fluorescence microscopy. Bar, 50 µm.