title: Developmental regulation and downstream effects of the knox class homeobox genes Oskn2 and Oskn3 from rice.
abstract: Plant homeobox genes of the class 1 knox (knotted1-like) type are involved in the regulation of shoot apical meristem formation and function. Their expression generally occurs either throughout the meristem or specifically at the lateral organ boundaries. Down-regulation in the organ primordia is tightly controlled and misexpression in leaves leads to a perturbed development. Here, the transcriptional control of two rice knox genes, Oskn2 and Oskn3, was addressed, showing that the promoter sequences of both genes mediate the initial down-regulation during lateral organ formation, but are insufficient to keep expression in lateral organs stably off. Therefore, maintenance of the repressed state requires control elements outside the promoter regions. Ectopic expression of Oskn2 or Oskn3 induced similar defects in panicle branching. internode elongation and leaf patterning. However, small differences suggested that their target gene specificities are not completely overlapping. This was supported by the observation that Oskn3 protein but not Oskn2 could interact with two reported recognition sequences of a KNOX protein from barley. Finally, protein-protein interactions may contribute to the functioning of KNOX proteins, as the ability of Oskn3 and Oskn2 to form heterodimers could be demonstrated.
authors.affiliation: Institute of Molecular Plant Sciences, Leiden University, Clusius Laboratory, The Netherlands.
authors.forename: A Dorien
authors.initials: AD
authors.lastname: Postma-Haarsma
authors.forename: Saskia
authors.initials: S
authors.lastname: Rueb
authors.forename: Enrico
authors.initials: E
authors.lastname: Scarpella
authors.forename: Willem
authors.initials: W
authors.lastname: den Besten
authors.forename: J Harry C
authors.initials: JH
authors.lastname: Hoge
authors.forename: Annemarie H
authors.initials: AH
authors.lastname: Meijer
mesh_terms: D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D019281:Dimerization; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox; D017343:Genes, Plant / Q000235:genetics; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D005966:Glucuronidase