title: The UCU1 Arabidopsis gene encodes a SHAGGY/GSK3-like kinase required for cell expansion along the proximodistal axis.
abstract: Most signal transduction pathways central to development are not shared by plants and animals. Such is the case of the Wingless/Wnt signaling pathway, whose components play key roles in metazoan pattern formation and tumorigenesis, but are absent in plants, with the exception of SHAGGY/GSK3, a cytoplasmic protein kinase represented in the genome of Arabidopsis thaliana by a family of 10 AtSK genes for which mutational evidence is scarce. Here, we describe the characterization of mutant alleles of the Arabidopsis ULTRACURVATA1 (UCU1) gene, the two strongest of which dramatically reduce cell expansion along the proximodistal axis, dwarfing the mutant plants, whose cells expand properly across but not along most organs. Proximodistal expansion of adaxial (dorsal) and abaxial (ventral) leaf cells exhibits a differential dependence on UCU1 function, as suggested by the leaves of ucu1 mutants, which are rolled spirally downward in a circinate manner. We have positionally cloned the UCU1 gene, which encodes an AtSK protein involved in the cross-talk between auxin and brassinosteroid signaling pathways, as indicated by the responses of ucu1 mutants to plant hormones and the phenotypes of double mutants involving ucu1 alleles.
authors.affiliation: División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Pérez-Pérez
authors.forename: María Rosa
authors.initials: MR
authors.lastname: Ponce
authors.forename: José Luis
authors.initials: JL
authors.lastname: Micol
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D019070:Cell Lineage; D003001:Cloning, Molecular; D017931:DNA Primers; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D011494:Protein Kinases
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C448985:At4g18710 protein, Arabidopsis; D011494:Protein Kinases