Figure 4.

Polar secretion of NtPPME that contributes to cell plate formation during cytokinesis is distinct from the endocytic pathway in tobacco BY2 cells. A, Polar secretion of NtPPME1 was not overlapped with endocytic dye FM4-64 (1) and insensitive to the 10 μg mL⁻¹ BFA treatment (2). Transgenic tobacco BY2 cells expressing GFP-AtSCAMP3 used as a control (3 and 4). Scale bar = 50 µm. B, Time-lapse images of cell plate initiation and formation in tobacco BY2 cell. (1) NtPPME1-GFP on the forming cell plate. (2) FM4-64-labeled endocytic membrane on the forming cell plate. Scale bar = 75 µm. The ImageJ program with the PSC colocalization plug-in (see “Materials and Methods”) was used to calculate the colocalizations between these two fluorophores. Results are presented either as Pearson correlation coefficients or as Spearman’s rank correlation coefficients, both of which produce r values in the range −1 to 1, where 0 indicates no discernable correlation while +1 and −1 indicate strong positive or negative correlations, respectively.