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Fig. 2. Protein trafficking from mesophyll to epidermal cells in the
Arabidopsis leaf. GFP fusion reporters were expressed using the
mesophyll-specific pRbcS2b-GAL4/UAS-reporter system. The
tissue specificity of the promoter is shown by the expression of the
cell-autonomous mGFP5-ER reporter. (A-C) Expanded leaves of transgenic plants
expressing mGFP5-ER showed GFP fluorescence in mesophyll and epidermal guard
cells, but not in epidermal pavement cells. (D-L) In contrast, the presence of
GFP KN1 (D-F), GFPTVCV MP (G-I) and free GFP (J-L) under the same
promoter was detected in all epidermal and subepidermal cells. (F) GFPKN1
and (I) GFPTVCV MP localized to puncta (arrowheads) that were not
observed in plants expressing free GFP (L). Hand-made cross sections
(A-B,D-E,G-H,J-K) were imaged by using red and green channels (left column)
and green channel only (middle column) of the confocal microscope. Paradermal
images are shown in (C,F,I,L). Left panels of A and D show bright-field images
of mGFP5-ER and GFPKN1 plant sections, respectively. (M-O)
Immunolocalization using an anti-KN1 antiserum was performed on leaf sections
of wild-type (M, red box is magnified in upper panel of O) and GFPKN1
expressing plants (N, red box is magnified in lower panel of O). GFPKN1
protein was detected in nuclei of epidermal cells and in mesophyll cells.
Arrows indicate nuclear localization of GFP and GFP fusions (F, I, L) and KN1
protein (O). Scale bars: 50 µm (A,B,D,E,G,H,J,K,M); 25 µm
(C,F,I,L,N,O).
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