Extended Data Fig. 4: Segregation errors in LexA-CENH3(v2) ABS4 plants.

a) Mitotic errors. Root tips from five sectored seeds were processed for FISH and the number of Cent4 and ABS spots counted in interphase nuclei. Two Cent4 (red) spots were observed in all nuclei. ABS (green), which is on one copy of chromosome 4, showed high frequencies of mis-segregation consistent with the model in Fig. 2a. The images shown above are examples. The two cells in the right image are daughter cells of a single division, where the left cell has no ABS and the right cell as two ABS loci. b) Meiotic errors. Three plants heterozygous for LexA-CENH3(v2) and ABS4 were analyzed at meiosis (siblings from a single ear). Only cells in mid-anaphase I, identified by the short distance between segregating chromosomes masses, were tallied. Figures with no recombination between the centromere and ABS4 were identified by having ABS dots only on one side (first column). Cases where recombination occurred and ABS4 loci segregated freely to one pole were identified by having one ABS dot on both sides (second column). Figures with bridges invariably had one or two ABS dots in the midzone, suggesting there had been recombination between centromere and ABS4, and that centromere cohesion at ABS4 restrained movement. At late anaphase I and telophase I, no intact bridges were observed.