Figure 7.

Inhibition of myosin causes CSC insertion failures at the PM. A, Representative images show a typical CSC insertion event at the PM. A CESA particle (yellow arrowhead) arriving in the cortex initially undergoes erratic motility, which likely represents a delivery vesicle (V) that is transported to an exocytosis site. The particle then pauses (marked as 0 s) and exhibits a static phase for ∼80 s in a fixed position, which likely corresponds to tethering, docking, and fusion of the delivery compartment to the PM. After the CSC particle is inserted, it shows steady movement at the PM as an active complex. T, Tethering proteins. Bar, 1 µm. B, Representative kymograph of the CSC insertion event shown in A illustrates the pause phase and the steady movement phase. The exact duration of the pause phase was determined by fitting a straight line (green) along the moving trajectory and another line (magenta) along the pause phase. The intersection of the two lines was defined as the end of the pause phase. C, Representative kymographs show five categories of insertion events from left to right: standard insertion with normal pause time, insertion that has a shorter pause time, insertion that has a longer pause time, a shorter pause time and failure to insert, and a longer pause time and failure to insert. Pause phases are marked with magenta dashed lines, and steady movement phases are marked with green dashed lines. Bar, 2 µm. D, Distribution of particle pause times (n ≥ 11 cells from seven seedlings for each genotype or treatment; a total of 114, 113, 124, 104, and 109 events were measured in wild type [WT], xi3KO, and BDM-, PBP-, and LatB-treated cells, respectively). E, The proportion of five types of insertion events described in C in wild-type, xi3KO, and BDM-, PBP-, and LatB-treated cells. A shorter or longer pause time was defined as the mean value (81 ± 27 s) of particle pause time in wild type minus (<54 s) or plus 1 sd (>108 s), respectively.