title: The defective kernel 1 (dek1) gene required for aleurone cell development in the endosperm of maize grains encodes a membrane protein of the calpain gene superfamily.
abstract: Endosperm of cereal grains is one of the most important renewable resources for food, feed, and industrial raw material. It consists of four triploid cell types, i.e., aleurone, starchy endosperm, transfer cells, and cells of the embryo surrounding region. In maize, the aleurone layer is one cell layer thick and covers most of the perimeter of the endosperm. Specification of maize aleurone cell fate is proposed to occur through activation of the tumor necrosis factor receptor-like receptor kinase CRINKLY4. A second maize gene essential for aleurone cell development is defective kernel 1 (dek1). Here we show that DEK1 shares high homology with animal calpains. The predicted 2,159-aa DEK1 protein has 21 transmembrane regions, an extracellular loop, and a cysteine proteinase domain that shares high homology with domain II of m-calpain from animals. We propose that DEK1 functions to maintain and restrict the aleurone cell fate imposed by CR4 through activation of its cysteine proteinase by contact with the outer endosperm surface. DEK1 seems to be the only member of the calpain superfamily in plants, Arabidopsis DEK1 sharing 70% overall identity with maize DEK1. The expression of dek1 in most plant tissues in maize and Arabidopsis, as well as its presence in a variety of higher plants, including angiosperms and gymnosperms, suggests that DEK1 plays a conserved role in plant signal transduction.
authors.affiliation: Department of Chemistry and Biotechnology, Agricultural University of Norway, 1432 As, Norway.
authors.forename: Stein Erik
authors.initials: SE
authors.lastname: Lid
authors.forename: Darren
authors.initials: D
authors.lastname: Gruis
authors.forename: Rudolf
authors.initials: R
authors.lastname: Jung
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Lorentzen
authors.forename: Evgueni
authors.initials: E
authors.lastname: Ananiev
authors.forename: Mark
authors.initials: M
authors.lastname: Chamberlin
authors.forename: Xiaomu
authors.initials: X
authors.lastname: Niu
authors.forename: Robert
authors.initials: R
authors.lastname: Meeley
authors.forename: Scott
authors.initials: S
authors.lastname: Nichols
authors.forename: Odd-Arne
authors.initials: OA
authors.lastname: Olsen
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000378:metabolism; D017343:Genes, Plant; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000502:physiology*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D003313:Zea mays / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D012313:RNA; D002154:Calpain; D003546:Cysteine Endopeptidases