Figure 4.

POM2/CSI1 Fluorescent Signals Associate with Microtubule Depolymerizing Ends.

(A) Images from time series (see Supplemental Movie 1 online) of cells in 4-d-old hypocotyls expressing mCherry:TUA5 and POM2:CFP treated with 100 nM isoxaben for 2 h. Yellow arrowheads indicate POM2/CSI1 fluorescent signal associated with a depolymerizing microtubule end. Right panel displays kymographs, which show that the POM2/CSI1 signal follows the microtubule retracting end.

(B) Time series (see Supplemental Movie 2 online) of POM2/CSI1 collecting other POM2/CSI1s. Yellow arrowheads indicate collecting POM2/CSI1 and red arrowheads collected POM2/CSI1s.

(C) Kymograph displaying POM2/CSI1 bidirectional migration (left), accelerating and stopping POM2/CSI1 (middle), and collecting POM2/CSI1 (right).

(D) Surface plot displayed as a heat map. The mean intensity of the signals above background was measured for the right kymograph in (C) and is displayed as relative values ± sd.

(E) Kymograph showing bifurcation and merge of POM2/CSI1 signal that is associated with a retracting microtubule end. When the end crosses another microtubule, the POM2/CSI1 signal bifurcates (yellow arrowheads). Merging events of two POM2/CSI1 signals happen along retracting microtubules that contain laterally associated POM2/CSI1 (red arrowheads).

Bars = 5 μm (A), (C), and (E) and 1 μM in (B).