Figure 2.

Regulation of Microtubule Severing by SPR2

(A) MT severing frequency in different cell types. Absence of severing in bot1-7 represents a negative control. Error bars show the SD between squared zones representing the different cells used for the analysis.

(B) Example of a WT Ler petiole cell arbitrarily divided into different regions with differing degrees of organization.

(C) Severing frequency is linearly correlated with crossover concentration. Data are based on the delimitation of 11 MT subpopulations from three WT petiole cells, as shown in (B).

(D) MT crossover density in petiole and pavement cells from different genotypes.

(E) SPR2 dynamics and intensity at MT crossover. The middle panel shows a kymograph of part of the MT depicted by the white line in the top panel. The white dotted line (middle panel) represents the crossover position over time. A plot of the intensity of the kymograph (bottom panel) gives the intensity of SPR2 at the crossover over time. The arrowhead and arrow mark the point at which severing occurred. In the right panel, individual images taken 1 s apart from the movie sequenced show that the severing occurs following the clearance of the crossover by a SPR2 particle that moves rapidly away from the crossover site (arrowhead). Scale bars represent 1 μm (left panels) and 2 μm (right panels).

(F) Distribution of SPR2 intensity at MT crossovers monitored over time in pavement and petiole cells. This distribution graph is based on ten crossovers in pavement and in petiole cells monitored each second for 1 min (600 s per cell type). SPR2 intensity is plotted in increments of 20 grayscale units; there is a maximum of 255 grayscale units for this image type.

See also Figure S3.