Peroxisome aggregation during cytokinesis in different angiosperm taxa

During cytokinesis in onion (Allium cepa L.) and leek (Allium porrum L.), all the peroxisomes present within the dividing cell aggregate in the phragmoplast adjacent to the developing cell plate. In order to understand the functional implications of this novel arrangement, especially in onion, which has hitherto been regarded as a model system in which to study plant cell division, we investigated how widespread the phenomenon was in selected monocots and dicots. During monocot cytokinesis, peroxisomes lacked aggregation in some taxa, notably grasses, and underwent partial aggregation in other taxa. However, complete aggregation of a cell's entire complement of peroxisomes was restricted to the genus Allium. Although peroxisomal aggregation has been suggested to function in the formation of the cell plate, the distribution of partial and complete aggregation in monocots did not match known differences in primary cell wall biochemistry. No aggregation was seen during cytokinesis in dicots. Through quantification of peroxisome distribution in cells whose actin microfilaments were disrupted with either latrunculin or cytochalasin, we demonstrated that peroxisomal aggregation is a microfilament-dependent process in Allium and the closely related plant Tristagma, which shows only partial aggregation. We speculate whether analysis of the peroxisomal proteome might reveal novel function(s) for aggregated peroxisomes during cytokinesis.