A dual role for PI4Kβ in endocytosis and phragmoplast dynamics during plant somatic cytokinesis (2018)
Figure 5

Figure 5. Impaired endocytosis in the Arabidopsis pi4kβ1 pi4kβ2 double mutant.

Experiments were performed to address possible effects of the pi4kβ1 pi4kβ2 double mutant on endocytosis of markers relevant for cell plate formation. Panels a-f display data obtained using cytokinetic cells; panels g-j display data from the analysis of interphase cells.

(a) Five-day-old seedlings were immunostained with anti-KNOLLE (green) and counterstained with DAPI (blue). In the pi4kβ1 pi4kβ2 double mutant, diffusion of KNOLLE occurred at the plasma membrane (arrowheads). Scale bars, 10 μm.

(b) Quantitative analysis of lateral diffusion of KNOLLE at the plasma membrane (PM) from (A). Data are mean ± SD from four independent experiments. **, a significant difference (p<0.01) according to a two-tailed Student's t test (untreated wild type, n= 97 cells, 25 roots; untreated pi4kβ1 pi4kβ2, n = 142 cells, 44 roots; BFA treated wild type, n = 126 cells, 28 roots; BFA treated pi4kβ1 pi4kβ2, n = 183 cells, 43 roots).

(c) Enhanced accumulation of KNOLLE at the cell plate at the end of cytokinesis in the pi4kβ1 pi4kβ2 double mutant. Five-day-old seedlings were immunostained with anti-KNOLLE antibodies (green) and counterstained with DAPI (blue). Scale bars, 10 μm.

(d) Quantification of KNOLLE intensity at the cell plate from (C), normalized to the signal intensity of intracellular compartments. ***, a significant difference (p<0.0001) according to a two-tailed Mann-Whitney U-test (wild type, n = 26 cells, 20 roots; pi4kβ1 pi4kβ2, n = 41 cells, 37 roots).

(e) Enhanced accumulation of PIN2-GFP at the cell plate at the end of cytokinesis in the the pi4kβ1 pi4kβ2 double mutant. Five-day-old seedlings were stained with 2 μM FM 4-64 for 3 minutes at room temperature. Scale bars, 10 μm.

(f) Quantification of PIN2-GFP signal at the cell plate from (E), normalized to the intensity at the apical plasma membrane intensity, as indicated by the dashed lines. ***, a significant difference (p<0.001) according to a two-tailed Mann-Whitney U-test (wild type, n = 28 cells, 16 roots; pi4kβ1 pi4kβ2, n = 45 cells, 26 roots).

(g) Internalization of PIN2-GFP was tracked overtime in live roots pretreated with 50 μM CHX for 30 min, then washed and incubated with 50 μM CHX and 25 μM BFA. Scale bars, 10 μm.

(h) Quantification of punctate signals from (G) induced by BFA in wild type and pi4kβ1 pi4kβ2 double mutants. Data are mean ± SD. *, a significant difference (p<0.05) according to a two-tailed Student's t test; (wild type, n = 116 cells, 6 roots; pi4kβ1 pi4kβ2, n = 110 cells, 7 roots).

(i) Delayed internalization of FM 4-64 from the plasma membrane in the pi4kβ1 pi4kβ2 double mutant. Four-day-old seedlings were pulsed with 2 μM FM 4-64 for 3 minutes on ice and then fluorescence was recorded for 20 min. Scale bars, 10 μm.

(j) Quantification of intracellular FM 4-64 signal from (i), normalized to apical and basal plasma membrane intensities. ***, a significant difference (p<0.0001) according to a two-tailed Mann-Whitney U-test (wild type, n = 116 cells, 6 roots; pi4kβ1 pi4kβ2, n = 66 cells, 9 roots).