Rapid minus-end depolymerization causes lower severing probability at crossovers in the spr2-2 mutant. (A) Observed probabilities of MT severing events per crossover in WT (n = 1,266 events in six cells) and spr2-2 plants (n = 1,056 in six cells). The asterisks indicate a significant difference by Fisher’s exact test (***, P < 0.001). (B) Boxplots for lifetime of MT crossovers with severing (n = 484 from WT and n = 251 from spr2-2; no significant difference by Mann–Whitney U test). (C) MT and SPR2 signal intensities at crossovers. Top: Relative mCherry-TUA5 intensity during crossover formation. Middle: Relative SPR2-GFP intensity during crossover formation. Bottom: SPR2-GFP to mCherry-TUA5 signal intensity ratio during crossover formation. Gray background indicates the time where the crossover is present (n = 547 crossovers in six cells). (D) Boxplots for lifetime of MT crossover without severing (n = 782 from WT and n = 810 from spr2-2). The asterisks indicate a significant difference by Mann-Whitney U test (***, P < 0.001). (E) Fraction of crossovers resolved, classified as caused by either plus-end or minus-end depolymerization in WT (n = 782 crossovers in six cells) and spr2-2 plants (n = 810 crossovers in six cells). In the boxplots, the box represents the range from 25th to 75th percentile, the horizontal line marks the median value and the whiskers span from the 2.5 to 97.5 percentile. The error bars in A represent the 95% confience interval (CI), and the error bars in C represent the SEM.