title: The Arabidopsis transcription factor LUH/MUM1 is required for extrusion of seed coat mucilage.
abstract: During differentiation, the Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells secrete mucilage composed primarily of rhamnogalacturonan I that is extruded from the seed coat upon imbibition. The mucilage of the mucilage modified1 (mum1) mutant contains rhamnogalacturonan I that is more highly branched and lacks the ability to be extruded when exposed to water. Our cloning of the MUM1 gene shows that it encodes a putative transcription factor, LEUNIG_HOMOLOG (LUH). Cellular localization and transcriptional assay results suggest that LUH/MUM1 is a nucleus-localized transcriptional activator. LUH/MUM1 is expressed in all the tissues examined, including the seed coat. Quantitative reverse transcription-polymerase chain reaction data suggest that LUH/MUM1 is expressed throughout seed coat development, reaching peak expression late in differentiation. LUH1/MUM1 expression in plants homozygous for mutations in several genes encoding regulators of seed coat mucilage was unchanged. Thus, LUH/MUM1 expression appears to be independent of other transcription factors known to regulate aspects of seed coat mucilage biology. The expression in the luh/mum1 mutant of three genes encoding enzymes needed for mucilage extrusion, MUM2, SUBSILIN PROTEASE1.7, and β-XYLOSIDASE1, was reduced relative to that of the wild type. Overexpression of MUM2 could partially rescue the mum1 phenotype. These data suggest that LUH/MUM1 is a positive regulator of all three genes.
authors.affiliation: Botany Department, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Jun
authors.initials: J
authors.lastname: Huang
authors.forename: Danisha
authors.initials: D
authors.lastname: DeBowles
authors.forename: Elahe
authors.initials: E
authors.lastname: Esfandiari
authors.forename: Gillian
authors.initials: G
authors.lastname: Dean
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Carpita
authors.forename: George W
authors.initials: GW
authors.lastname: Haughn
mesh_terms: D000269:Adhesives / Q000378:metabolism*; D000468:Alkalies / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002241:Carbohydrates / Q000032:analysis; D002614:Chelating Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008040:Genetic Linkage / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D030821:Plants, Genetically Modified; D021381:Protein Transport / Q000187:drug effects; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics
chemical_list: D000269:Adhesives; D000468:Alkalies; D029681:Arabidopsis Proteins; D002241:Carbohydrates; D002614:Chelating Agents; C560407:LUH protein, Arabidopsis; D012097:Repressor Proteins; D014157:Transcription Factors