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Title: ACTIN-DEPENDENT ASSOCIATION OF PEROXISOMES WITH THE DEVELOPING CELL PLATE DURING CYTOKINESIS IN ONION ROOT TIP CELLS

Author
item COLLINGS, DAVID - AUSTRALIAN NAT'L UNIV
item HARPER, JOHN - CHARLES STUART UNIV -AUS
item Vaughn, Kevin

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2003
Publication Date: 8/21/2003
Citation: Collings, D.A., Harper, J.D., Vaughn, K.C. 2003. Actin-dependent association of peroxisomes with the developing cell plate during cytokinesis in onion root tip cells. Planta Journal. 218:204-216.

Interpretive Summary: When plant cells divide, they form a structure called the cell plate that serves to separate the daughter nuclei and cytoplasm. Previous investigations have noted that a number of herbicides affect the cell plate formation but the exact mechanism for this disruption is not known. This paper documents the presence of two organelles in the cell plate, peroxisomes and actin microfilaments. Each of these organelles appears to be critical in producing a cell plate and are structures which may be affected by herbicides, so that cell plate formation is disrupted. These findings are important because they explain previous results of herbicide action as being due to effects on the peroxisomes. This is a novel site of action.

Technical Abstract: We have investigated changes in the distribution of peroxisomes in onion root tip cells through the cell cycle using confocal and electron microscopy. During interphase and mitosis, peroxisomes distribute randomly throughout the cytoplasm, but beginning late in anaphase, all peroxisomes accumulate at the division plane. Initially, peroxisomes occur within the microtubule phragmoplast in two zones on either side of the developing cell plate. However, as the phragmoplast matures and expands outwards to form an annulus, peroxisomes redistribute into a ring immediately inside the location of the microtubules. This aggregation of peroxisomes adjacent to the cell plate and phragmoplast is an actin-dependent process. Peroxisomes first accumulate in the division plane prior to the formation of the microtubule phragmoplast, and throughout cytokinesis, always codistribute with actin. Electron micrographs, which show some peroxisomes in close association with vesicles near the cell plate, also confirm a direct interaction between the peroxisomes and actin. Furthermore, application of cytochalasin, latrunculin and the myosin-antagonist BDM inhibit aggregation. The phenomenon of peroxisome aggregation adjacent to the cell plate is most pronounced in onion and a range of other monocots, and occurs in some dicots including tobacco BY-2 cells but not in the roots of Arabidopsis. We propose that peroxisomes function in the formation of the cell plate, either by regulating hydrogen peroxide formation within the developing cell plate, or by their involvement in recycling of excess membranes from secretory vesicles via the *-oxidation pathway.