Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis.
In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.
Western
T L
TL
Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4.
Burn
J
J
Tan
W L
WL
Skinner
D J
DJ
Martin-McCaffrey
L
L
Moffatt
B A
BA
Haughn
G W
GW
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D029681:Arabidopsis Proteins; D002454:Cell Differentiation; D002473:Cell Wall / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D005306:Fertilization; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D009024:Morphogenesis; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010368:Pectins / Q000096:biosynthesis* / Q000378:metabolism; D010641:Phenotype; D019441:Plant Epidermis / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012430:Ruthenium Red; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D015053:Zygote / Q000254:growth & development; D001616:beta-Galactosidase
C499534:APETALA2 protein, Arabidopsis; D029681:Arabidopsis Proteins; C089991:GL2 protein, Arabidopsis; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; C121067:TTG1 protein, Arabidopsis; D012430:Ruthenium Red; D010368:Pectins; C000597451:MUM2 protein, Arabidopsis; D001616:beta-Galactosidase