title: HIGHLY METHYL ESTERIFIED SEEDS is a pectin methyl esterase involved in embryo development.
abstract: Homogalacturonan pectin domains are synthesized in a highly methyl-esterified form that later can be differentially demethyl esterified by pectin methyl esterase (PME) to strengthen or loosen plant cell walls that contain pectin, including seed coat mucilage, a specialized secondary cell wall of seed coat epidermal cells. As a means to identify the active PMEs in seed coat mucilage, we identified seven PMEs expressed during seed coat development. One of these, HIGHLY METHYL ESTERIFIED SEEDS (HMS), is abundant during mucilage secretion, peaking at 7 d postanthesis in both the seed coat and the embryo. We have determined that this gene is required for normal levels of PME activity and homogalacturonan methyl esterification in the seed. The hms-1 mutant displays altered embryo morphology and mucilage extrusion, both of which are a consequence of defects in embryo development. A significant decrease in the size of cells in the embryo suggests that the changes in embryo morphology are a consequence of lack of cell expansion. Progeny from a cross between hms-1 and the previously characterized PME inhibitor5 overexpression line suggest that HMS acts independently from other cell wall-modifying enzymes in the embryo. We propose that HMS is required for cell wall loosening in the embryo to facilitate cell expansion during the accumulation of storage reserves and that its role in the seed coat is masked by redundancy.
authors.affiliation: Departments of Botany (G.L.-T., G.W.H.) andWood Science (S.D.M.), Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4; andDepartment of Biological Science, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (K.M.).
authors.forename: Gabriel
authors.initials: G
authors.lastname: Levesque-Tremblay
authors.affiliation: Departments of Botany (G.L.-T., G.W.H.) andWood Science (S.D.M.), Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4; andDepartment of Biological Science, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (K.M.).
authors.forename: Kerstin
authors.initials: K
authors.lastname: Müller
authors.affiliation: Departments of Botany (G.L.-T., G.W.H.) andWood Science (S.D.M.), Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4; andDepartment of Biological Science, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (K.M.).
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Mansfield
authors.affiliation: Departments of Botany (G.L.-T., G.W.H.) andWood Science (S.D.M.), Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4; andDepartment of Biological Science, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 (K.M.) george.haughn@ubc.ca.
authors.forename: George W
authors.initials: GW
authors.lastname: Haughn
mesh_terms: D000906:Antibodies / Q000378:metabolism; D017360:Arabidopsis / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001696:Biomechanical Phenomena; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D048429:Cell Size; D004951:Esterification; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D016254:Mutagenesis, Insertional; D010368:Pectins / Q000378:metabolism; D010641:Phenotype; D062087:Plant Mucilage / Q000378:metabolism; D030821:Plants, Genetically Modified; D012639:Seeds / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure
chemical_list: D000906:Antibodies; D029681:Arabidopsis Proteins; D062087:Plant Mucilage; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C000604152:HIGHLY METHYL ESTERIFIED SEEDS protein, Arabidopsis; C022323:pectinesterase; C003181:polygalacturonic acid