Fig. 4. The extra cells in the Xcl1 mutant have epidermal identity. (A-F) Immunolocalizations with cell-type-specific antibodies. Silver enhancement of the gold-conjugated secondary antibody produced a black signal. (A,B) The small subunit of RuBisCO is localized to the bundle sheath cells in both wild-type (A) and Xcl1 (B) leaves, but is not detected in the extra cell layer. (C,D) PEPC is localized to the mesophyll cells in wild-type (C) and Xcl1 (D) leaves, but is not in the extra cell layer. (E-F) ß (1,3) and (1,4) mixed linkage glucans are localized to epidermal and vascular cell walls in wild-type leaves (E) and in the extra cell layers in the Xcl1 mutant (F). (G) Anthocyanin production is limited to the epidermis in the adult wild-type leaf. (H) Anthocyanins are produced in both the epidermis and the extra cell layers in Xcl1. (I-J) ZmOCL5 is expressed in the outer cell layer in both wild-type (I) and Xcl1 (J) meristems and leaves. Scale bars A-J, 100 µm.