Fig. 1: Root-restricted elimination of B chromosomes starts with radicle formation at the onset of embryo differentiation of Ae. speltoides.

a Flow cytometric histograms representing the DNA content of nuclei of 17 DAP 0B and +B embryos. Black peaks correspond to 0B nuclei with 2C or 4C DNA content and red peaks correspond to nuclei containing B chromosomes. The presence of additional 0B peaks in +B embryos implies that the elimination of Bs had been initiated prior to this stage of embryogenesis. Tissue sections (b, c) of +B embryos and (d) seedling after FISH using the B-specific probe AesTR-183. For each stage of embryo/plant development 2–4 embryos/seedlings were sectioned and analyzed. Obtained results were consistent. b Embryo at the stage of 5 DAP exhibits B-specific signals in all cells. Scale bar, 10 µm. c 15 DAP old embryo exhibiting complete absence of Bs in root cells. Root region is indicated by arrowheads. Scale bar, 100 µm. d Tissue section of a one-day-old seedling. The transition zone between B-positive leaf and B-negative root tissues is marked by yellow dotted lines. Scale bar, 100 µm. The insert shows the seedling with the sectioning plane marked by a black dashed line. Scale bar, 5 mm.