Figure 4.

The disruption of polar auxin transport induced the LlZEP gene and altered the ABA localization in the abscission zone area. The relative level of LlZEP (zeaxanthin epoxidase) transcripts was investigated using qPCR (A). A solution of 2,3,5-triiodobenzoic acid (TIBA, 0.05 mM in 0.05% Tween 20) or 0.05% Tween 20 was applied directly on the inactive flower abscission zone (AZ). Subsequently, the tissue fragments containing the AZ (≈1 mm below and ≈1 mm above) were dissected 4 h or 6 h after treatments and divided into a proximal (PROX) and a distal (DIST) part for further RNA isolation. LlACT (actin) was used as an internal control for the normalization of gene expression. Values represent mean ± SD (n = 3). Error bars indicate SEs. t-test: ^a p < 0.05, TIBA-treated distal part versus Tween 20-treated distal part for different times after application; ^bb p < 0.01 and ^b p < 0.05, TIBA-treated proximal part versus Tween 20-treated proximal part for different times after application, ^## p < 0.01, proximal versus distal part in the TIBA-treated AZ for different times after application. Immunofluorescence localization of ABA in the AZ area (B). Magnified region of the AZ (C). P—proximal side, D—distal side. Observations were carried out 6 h after the TIBA application. The presence of green fluorescence indicates ABA localization (marked by red arrowheads). Scale bars: 40 µM.