| Cell separation is important to many plant growth processes including germination, fruit ripening, seed dehiscence, and abscission of fruit and vegetative tissues. Understanding how separation and adhesion are regulated may increase our ability to manipulate plants for improved yields, fruit quality, digestibility, and longevity. Abscission, the removal of an organ from the main body of the plant, is an excellent process to study cell separation. The process of abscission includes differentiation of cells in the abscission zone, initiation of abscission leading to cell wall modifications and middle lamella degradation, and finally the generation of a protective scar covering the abscission zone. We have characterized a delayed abscission mutant, dab5-1, in Arabidopsis thaliana that retains its petals significantly longer than wild type. The delayed abscission phenotype in dab5-1 is caused by a T-DNA insertion upstream of SECRETORY CARRIER MEMBRANE PROTEIN5 (SCAMP5). SCAMP genes have been identified in many other multi-cellular organisms and there is evidence that these proteins are involved in vesicle formation and protein trafficking within the cell. Mutations in the other four SCAMP genes in Arabidopsis do not cause an abnormal phenotype, suggesting there may be redundancy within the family. However, silencing of multiple SCAMPs below 40% of wild type levels results in detrimental growth defects. We hypothesize that the delay in abscission and the growth defects are due to a change in vesicle trafficking. Further studies of SCAMPs will help to better characterize the secretory system in plants, refine our understanding of SCAMP function, and increase our understanding of the role of protein trafficking in abscission. |
