Fig. 3. GFPKN1 does not traffic from epidermal to sub-epidermal cells in the leaf. GFP fusion reporters were expressed using the epidermis-specific pLTP1 or pAtML1 promoters in the GAL4/UAS-reporter system. Expression of the cell-autonomous mGFP5-ER reporter (A-C) under the control of pLTP1 showed the epidermal specificity of pLTP1 in expanded leaf (A,C) and in hypocotyl (B). Similarly, GFPKN1 was restricted to epidermal cells of expanded leaf (D) and hypocotyl (E). Note that the weak fluorescence in mesophyll cell layers in A and D is autofluorescence that is inevitable in sectioned plant tissues. (F) Epidermally expressed GFPKN1 does not show punctate cell wall spots of green fluorescence. pAtML1 expression similarly resulted in epidermis-specific localization of GFPKN1 in young leaf primordia (G,H, lower panel) and mGFP5-ER (H, upper panel). (I-K) In contrast, GFP (I) and GFPTVCV MP (J) expressed under the control of pLTP1 showed extensive movement and GFPTVCV MP localized to PDs (K). (L) A control root expressing mGFP5-ER under the control of pAtML1 does not show any green fluorescence over background levels (L, upper panel). In contrast, the GFPTVCV MP fusion produced in shoot epidermal cells could also be detected in root vascular and cortical tissues (lower panel), indicating its long distant trafficking. C,F,K are paradermal and A,B (inset) D, E (inset) and G-J are cross sections. Inset images and paradermal images are red/green channel images. Yellow arrows indicate nuclei; arrowheads show punctate cell wall spots. Scale bars: 25 µm (C,F,K,H); 50 µm (A,B,D,E,I,J,L); 100 µm (G).

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