title: Spatiotemporal secretion of PEROXIDASE36 is required for seed coat mucilage extrusion in Arabidopsis.
abstract: The epidermal cells of the Arabidopsis thaliana seed coat, which correspond to the second layer of the outer integument (oi2), contain large quantities of a pectic polysaccharide called mucilage within the apoplastic space beneath the outer periclinal cell wall. Immediately after seed imbibition, the mucilage is extruded and completely envelops the seed in a gel-like capsule. We found that a class III peroxidase family protein, PEROXIDASE36 (PER36), functions as a mucilage extrusion factor. Expression of PER36 occurred only in oi2 cells for a few days around the torpedo stage. A PER36-green fluorescent protein fusion was secreted into the outer cell wall in a polarized manner. per36 mutants were defective in mucilage extrusion after seed imbibition due to the failure of outer cell wall rupture, although the mutants exhibited normal monosaccharide composition of the mucilage. This abnormal phenotype of per36 was rescued by pectin solubilization, which promoted cell wall loosening. These results suggest that PER36 regulates the degradation of the outer cell wall. Taken together, this work indicates that polarized secretion of PER36 in a developmental stage-dependent manner plays a role in cell wall modification of oi2 cells.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kunieda
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.forename: Maki
authors.initials: M
authors.lastname: Kondo
authors.forename: Mikio
authors.initials: M
authors.lastname: Nishimura
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishitani
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009154:Mutation; D009195:Peroxidase / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D062087:Plant Mucilage / Q000378:metabolism*; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D062211:Spatio-Temporal Analysis; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D062087:Plant Mucilage; D049452:Green Fluorescent Proteins; C585249:PER36 protein, Arabidopsis; D010544:Peroxidases; D009195:Peroxidase