title: PHANTASTICA regulates development of the adaxial mesophyll in Nicotiana leaves.
abstract: Initiation and growth of leaf blades is oriented by an adaxial/abaxial axis aligned with the original axis of polarity in the leaf primordium. To investigate mechanisms regulating this process, we cloned the Nicotiana tabacum ortholog of PHANTASTICA (NTPHAN) and generated a series of antisense transgenics in N. sylvestris. We show that NSPHAN is expressed throughout emerging blade primordia in the wild type and becomes localized to the middle mesophyll in the expanding lamina. Antisense NSPHAN leaves show ectopic expression of NTH20, a class I KNOX gene. Juvenile transgenic leaves have normal adaxial/abaxial polarity and generate leaf blades in the normal position, but the adaxial mesophyll shows disorganized patterns of cell division, delayed maturation of palisade, and ectopic reinitiation of blade primordia along the midrib. Reversal of the phenotype with exogenous gibberellic acid suggests that NSPHAN, acting via KNOX repression, maintains determinacy in the expanding lamina and sustains the patterns of cell proliferation critical to palisade development.
authors.affiliation: Department of Biochemistry and Genetics, Conecticut Agricultural Experiment Station, New Haven, Conecticut 06504, USA. neil.mchale@po.state.ct.us
authors.forename: Neil A
authors.initials: NA
authors.lastname: McHale
authors.forename: Ross E
authors.initials: RE
authors.lastname: Koning
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000235:genetics; D008969:Molecular Sequence Data; D009030:Mosaicism / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development*
chemical_list: D010940:Plant Proteins; D020598:Proto-Oncogene Proteins c-myb