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 reported that plant-specific NAC transcription factors, NARS1 and NARS2, are involved in accumulation of the mucilage (1). A large number of genes (>300 genes) were remarkably down-regulated in developing seeds of nars1 nars2 double mutant. In these genes, we focused on a seed-coat specific peroxidase (PER). PER-GFP fusion protein was specifically localized to the outer cell wall of the mucilage-accumulation cells. The per knockdown mutant showed partial extrusion of the mucilage and failed to form the mucilage gel-matrix. This abnormal mucilage extrusion of per mutant was complemented by chemical treatments such as EDTA and Na2CO3, which cause cell wall loosening. These results indicate that PER is involved in cell wall degradation and promotes the mucilage extrusion in the mucilage-accumulation cells.
(1) Kunieda et al., Plant Cell, 20, 2631-2642 (2008).