ABC transporters are evenly localized in plasma membranes during protoxylem TE differentiation in VND7-VP16-GR seedlings. A, Maximum projection image of cotyledon epidermal cells undergoing protoxylem TE differentiation, expressing GFP-ABCG33. B, Cellulose stain, Pontamine S4B, counterstained image of cells shown in A, highlighting secondary cell wall domains. C, Median optical slice of induced protoxylem TE, showing invaginations of GFP-ABCG33 (green), counterstained with Pontamine S4B (red) demonstrating secondary cell wall domains, with inset image of the optical cross section of one secondary wall thickening. D, Induced protoxylem TE from plants expressing GFP-ABCG29, with inset showing plasma membrane localization over primary and secondary wall domains. Bars = 15 μm.