Abstract
We previously demonstrated that rice (Oryza sativa) SECRETORY CARRIER MEMBRANE PROTEIN1 (OsSCAMP1)-yellow fluorescent protein in transgenic tobacco (Nicotiana tabacum) Bright Yellow-2 cells locates to the plasma membrane and to motile punctate structures, which represent the trans-Golgi network/early endosome and are tubular-vesicular in nature. Here, we now show that SCAMPs are diverted to the cell plate during cytokinesis dividing Bright Yellow-2 cells. As cells progress from metaphase to cytokinesis, punctate OsSCAMP1-labeled structures begin to collect in the future division plane. Together with the internalized endosomal marker FM4-64, they then become incorporated into the cell plate as it forms and expands. This was confirmed by immunogold electron microscopy. We also monitored for the Golgi apparatus and the prevacuolar compartment (PVC)/multivesicular body. Golgi stacks tend to accumulate in the vicinity of the division plane, but the signals are clearly separate to the cell plate. The situation with the PVC (labeled by green fluorescent protein-BP-80) is not so clear. Punctate BP-80 signals are seen at the advancing periphery of the cell plate, which was confirmed by immunogold electron microscopy. Specific but weak labeling was observed in the cell plate, but no evidence for a fusion of the PVC/multivesicular body with the cell plate could be obtained. Our data, therefore, support the notion that cell plate formation is mainly a secretory process involving mass incorporation of domains of the trans-Golgi network/early endosome membrane. We regard the involvement of multivesicular late endosomes in this process to be equivocal.
Highlights
We previously demonstrated that rice (Oryza sativa) SECRETORY CARRIER MEMBRANE PROTEIN1 (OsSCAMP1)-yellow fluorescent protein in transgenic tobacco (Nicotiana tabacum) Bright Yellow-2 cells locates to the plasma membrane and to motile punctate structures, which represent the trans-Golgi network/early endosome and are tubular-vesicular in nature
To study the dynamics of OsSCAMP1 during cytokinesis, we followed the distribution of fluorescent signals in a single dividing Bright Yellow-2 (BY-2) cell expressing OsSCAMP1-YFP
The signal coalesces into a single thick line corresponding to the cell plate (Fig. 1, panels 8–10). These results indicated that OsSCAMP1-YFP highlights the cell plate formation during cytokinesis in transgenic BY-2 cells
Summary
We previously demonstrated that rice (Oryza sativa) SECRETORY CARRIER MEMBRANE PROTEIN1 (OsSCAMP1)-yellow fluorescent protein in transgenic tobacco (Nicotiana tabacum) Bright Yellow-2 cells locates to the plasma membrane and to motile punctate structures, which represent the trans-Golgi network/early endosome and are tubular-vesicular in nature. Reichardt et al (2007) have shown that wortmannin, which targets the MVB/PVC (Tse et al, 2004; Lam et al, 2007a, 2007b), does not inhibit cytokinesis, whereas the V-ATPase inhibitor concanamycin A, which blocks trafficking at the transGolgi network (TGN), severely impairs cell plate formation Both Reichardt et al (2007) and Chow et al (2008) were unable to detect PVC markers (BP-80 and RAB-F2A/2B) at the cell plate; on the other hand, Rab-A2/A3, which in interphase cells normally locates to a TGN-early endosomal compartment, was detected at the cell plate. This was subsequently identified by immunogold electron microscopy (EM) with SCAMP1 and GFP antibodies as a tubular-vesicular structure resembling the TGN or a partially coated reticulum
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