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Cytokinesis is the process of partitioning the cytoplasm of a dividing cell, thereby completing mitosis. Cytokinesis in the plant cell is achieved by the formation of a new cell wall between daughter nuclei using components carried in Golgi-derived vesicles that accumulate at the midplane of the phragmoplast and fuse to form the cell plate. Proteins that play major roles in the development of the cell plate in plant cells are not well defined. Here, we report that an AP180 amino-terminal homology/epsin amino-terminal homology domain-containing protein from Arabidopsis (Arabidopsis thaliana) is involved in clathrin-coated vesicle formation from the cell plate. Arabidopsis Epsin-like Clathrin Adaptor1 (AtECA1; At2g01600) and its homologous proteins AtECA2 and AtECA4 localize to the growing cell plate in cells undergoing cytokinesis and also to the plasma membrane and endosomes in nondividing cells. AtECA1 (At2g01600) does not localize to nascent cell plates but localizes at higher levels to expanding cell plates even after the cell plate fuses with the parental plasma membrane. The temporal and spatial localization patterns of AtECA1 overlap most closely with those of the clathrin light chain. In vitro protein interaction assays revealed that AtECA1 binds to the clathrin H chain via its carboxyl-terminal domain. These results suggest that these AP180 amino-terminal homology/epsin amino-terminal homology domain-containing proteins, AtECA1, AtECA2, and AtECA4, may function as adaptors of clathrin-coated vesicles budding from the cell plate.
Cytokinesis is the last stage of mitosis, in which the cytoplasm of a dividing cell is partitioned to daughter cells. Unlike animal cells, which divide by fission, plant cells employ a more complicated mechanism for cytokinesis: a phragmoplast, a cytokinetic organelle, is formed from the remains of spindle microtubules, and a new cell wall is generated at the midplane of the phragmoplast, thereby separating the cytoplasm (Jürgens, 2005). Secretory vesicles originating from the trans-Golgi network (TGN) are delivered to the division plane and fuse to each other via a homotypic fusion to form the cell plate (Mayer and Jürgens, 2004; Jürgens, 2005; Dhonukshe et al., 2006; Chow et al., 2008; Van Damme et al., 2008; Thiele et al., 2009; Reyes et al., 2011). The fused vesicles at the growing cell plate are then further processed via intermediate structures, such as tubulovesicular networks, to form planar fenestrated sheets...