title: Short tandem repeats shared by B- and C-hordein cDNAs suggest a common evolutionary origin for two groups of cereal storage protein genes.
abstract: We have identified cDNA clones coding for the major sulphur-rich and sulphur-poor groups of barley storage proteins (the B- and C-hordeins, respectively). Hybridization studies have revealed unexpected homologies between B- and C-hordein mRNAs. Using a deletion mutant (Risø 56), we have mapped some C-hordein-related sequences within, or closely associated with, B-hordein genes at the Hor 2 locus. Nucleotide sequencing has shown that the primary structure of B-hordein polypeptides can be divided into at least two domains: domain 1 (repetitive, proline-rich, sulphur-poor), which is homologous to C-hordein sequences, and domain 2 (non-repetitive, proline-poor, sulphur rich), which makes up two-thirds of the polypeptide and is partially homologous to a 2S globulin storage protein found in dicotyledons. The coding sequences that are homologous in B- and C-hordein mRNAs have an asymmetric base composition (>80% C-A) and are largely composed of a degenerate tandem repeat based on a 24 nucleotide consensus that encodes Pro-Gln-Gln-Pro-Phe-Pro-Gln-Gln. We discuss the evolutionary implications of the domain structure of the B-hordeins and the unusual relationship between the two groups of barley storage proteins.
authors.affiliation: Biochemistry Department, Rothamsted Experimental Station, Harpenden, Herts AL5 2JQ, UK.
authors.forename: B G
authors.initials: BG
authors.lastname: Forde
authors.forename: M
authors.initials: M
authors.lastname: Kreis
authors.forename: M S
authors.initials: MS
authors.lastname: Williamson
authors.forename: R P
authors.initials: RP
authors.lastname: Fry
authors.forename: J
authors.initials: J
authors.lastname: Pywell
authors.forename: P R
authors.initials: PR
authors.lastname: Shewry
authors.forename: N
authors.initials: N
authors.lastname: Bunce
authors.forename: B J
authors.initials: BJ
authors.lastname: Miflin
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017353:Gene Deletion; D005983:Glutens; D001467:Hordeum / Q000235:genetics; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D020080:Tandem Repeat Sequences / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D005983:Glutens