Figure 4. Tissue localization of the expression of VpVAN in transverse sections of a 6-month-old vanilla pod determined by in tube in situ PCR.

Transcripts of VpVAN were detected in specific cells (Panels a and b) using FITC-conjugated antibodies recognizing digoxigenin (DIG) incorporated in the specific PCR products representing the VpVAN transcript. Higher magnification of the selected area in Panel a is shown in Panel b. No transcripts of VpVAN were detected in the controls in the absence of specific primers for VpVAN (Panel c). The fluorescence detected in Panel c represents unspecific binding of the FITC-conjugated antibodies recognizing DIG to cell walls and supporting fibre cells surrounding the vascular systems. In all panels the chloroplasts are visible owing to their auto fluorescence at the used filter settings. The sections were analysed with a Leica FI/RH filter with excitation filters: BP490/15; 560/25 and emission filters: BP525/20; 605/30. e, epidermis; c, cortex; cl, chloroplast; s, supporting fibre tissue; Scale bar, 100 μm.