title: Cyclin-dependent kinase inhibitors in maize endosperm and their potential role in endoreduplication.
abstract: Two maize (Zea mays) cyclin-dependent kinase (CDK) inhibitors, Zeama;KRP;1 and Zeama;KRP;2, were characterized and shown to be expressed in developing endosperm. Similar to the CDK inhibitors in Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum), the maize proteins contain a carboxy-terminal region related to the inhibitory domain of the mammalian Cip/Kip inhibitors. Zeama;KRP;1 is present in the endosperm between 7 and 21 d after pollination, a period that encompasses the onset of endoreduplication, while the Zeama;KRP;2 protein declines during this time. Nevertheless, Zeama;KRP;1 accounts for only part of the CDK inhibitory activity that peaks coincident with the endoreduplication phase of endosperm development. In vitro assays showed that Zeama;KRP;1 and Zeama;KRP;2 are able to inhibit endosperm Cdc2-related CKD activity that associates with p13(Suc1). They were also shown to specifically inhibit cyclin A1;3- and cyclin D5;1-associated CDK activities, but not cyclin B1;3/CDK. Overexpression of Zeama;KRP;1 in maize embryonic calli that ectopically expressed the wheat dwarf virus RepA protein, which counteracts retinoblastoma-related protein function, led to an additional round of DNA replication without nuclear division.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Cintia M
authors.initials: CM
authors.lastname: Coelho
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Dante
authors.forename: Paolo A
authors.initials: PA
authors.lastname: Sabelli
authors.forename: Yuejin
authors.initials: Y
authors.lastname: Sun
authors.forename: Brian P
authors.initials: BP
authors.lastname: Dilkes
authors.forename: William J
authors.initials: WJ
authors.lastname: Gordon-Kamm
authors.forename: Brian A
authors.initials: BA
authors.lastname: Larkins
mesh_terms: D000595:Amino Acid Sequence; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis*; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics
chemical_list: D010940:Plant Proteins; D018844:Cyclin-Dependent Kinases