Abstract
Arabidopsis seed has a large quantity of polysaccharide "mucilage" in the apoplastic space underneath the outer cell wall of the seed coat. To protect the embryo from dehydration during germination, the mucilage is extruded from seed coat, and then forms a gel-matrix surrounding the seed.
We found that a class III peroxidase (PER) expressed transiently in the mucilage-accumulating cells. The per knockdown mutants showed partial extrusion of the mucilage. This abnormal mucilage extrusion of per mutants was rescued by chemical treatments such as EDTA and Na2CO3, which cause solubilisation of pectin. PER-GFP fusion protein which was controlled under PER promoter was preferentially localized to the outer cell wall of the mucilage-accumulating cells, suggesting that PER was involved in cell wall degradation of mucilage-accumulating cells. On the other hand, the filamentous structure of cell wall decreased in the mucilage of per mutants, compared with that of wild type. Some peroxidases have been identified to cause cross-linking between cell wall components. These results suggest that PER regulates both degradation and formation mechanisms of cell wall.
