title: Characterization of gibberellin receptor mutants of barley (Hordeum vulgare L.).
abstract: The sequence of Gid1 (a gene for a gibberellin (GA) receptor from rice) was used to identify a putative orthologue from barley. This was expressed in E. coli, and produced a protein that was able to bind GA in vitro with both structural specificity and saturability. Its potential role in GA responses was investigated using barley mutants with reduced GA sensitivity (gse1 mutants). Sixteen different gse1 mutants each carried a unique nucleotide substitution in this sequence. In all but one case, these changes resulted in single amino acid substitutions, and, for the remaining mutant, a substitution in the 5' untranslated region of the mRNA is proposed to interfere with translation initiation. There was perfect linkage in segregating populations between new mutant alleles and the gse1 phenotype, leading to the conclusion that the putative GID1 GA receptor sequence in barley corresponds to the Gse1 locus. Determination of endogenous GA contents in one of the mutants revealed enhanced accumulation of bioactive GA(1), and a deficit of C(20) GA precursors. All of the gse1 mutants had reduced sensitivity to exogenous GA(3), and to AC94377 (a GA analogue) at concentrations that are normally 'saturating', but, at much higher concentrations, there was often a considerable response. The comparison between barley and rice mutants reveals interesting differences between these two cereal species in GA hormonal physiology.
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia. peter.chandler@csiro.au
authors.forename: Peter M
authors.initials: PM
authors.lastname: Chandler
authors.forename: Carol A
authors.initials: CA
authors.lastname: Harding
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Ashton
authors.forename: Mark D
authors.initials: MD
authors.lastname: Mulcair
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Dixon
authors.forename: Lewis N
authors.initials: LN
authors.lastname: Mander
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002874:Chromosome Mapping; D005875:Gibberellins / Q000235:genetics* / Q000378:metabolism; D001467:Hordeum / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D012275:Oryza / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D020121:5' Untranslated Regions; D005875:Gibberellins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C007842:gibberellic acid