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First published online October 9, 2003; 10.1104/pp.103.026195 Plant Physiology 133:1209-1219 (2003) © 2003 American Society of Plant Biologists A Semidwarf Phenotype of Barley uzu Results from a Nucleotide Substitution in the Gene Encoding a Putative Brassinosteroid ReceptorDepartment of Wheat and Barley Research, National Institute of Crop Science, National Agricultural Research Organization, 2–1–18 Kannondai, Tsukuba, Ibaraki 305–8518, Japan (M.C., I.H., T.H., Y.W.); Department of Applied Biochemistry (H.Z.) and Center for Research on Wild Plants (K.Y.), Utsunomiya University, 350 Mine-machi, Utsunomiya, Tochigi 321–8505, Japan; Barley Germplasm Center, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710–0046, Japan (D.S., K.T.); and Department of Chemistry, Joetsu University of Education, Joetsu, Niigata 943–8512, Japan (S.T.)
Brassinosteroids (BRs) play important roles throughout plant growth and development. Despite the importance of clarifying the mechanism of BR-related growth regulation in cereal crops, BR-related cereal mutants have been identified only in rice (Oryza sativa). We previously found that semidwarf barley (Hordeum vulgare) accessions carrying the "uzu" gene, called "uzu" barley in Japan, are non-responding for brassinolide (BL). We then performed chemical and molecular analyses to clarify the mechanisms of uzu dwarfism using isogenic line pairs of uzu gene. The response of the uzu line to BL was significantly lower than that of its corresponding normal line. Measurement of BRs showed that the uzu line accumulates BRs, similar to known BR-insensitive mutants. The marker synteny of rice and barley chromosomes suggests that the uzu gene may be homologous to rice D61, a rice homolog of Arabidopsis BR-insensitive 1 (BRI1), encoding a BR-receptor protein. A barley homolog of BRI1, HvBRI1, was isolated by using degenerate primers. A comparison of HvBRI1 sequences in uzu and normal barley varieties showed that the uzu phenotype is correlated with a single nucleotide substitution. This substitution results in an amino acid change at a highly conserved residue in the kinase domain of the BR-receptor protein. These results may indicate that uzu dwarfism is caused by the missense mutation in HvBRI1. The uzu gene is being introduced into all hull-less barley cultivars in Japan as an effective dwarf gene for practical use, and this is the first report about an agronomically important mutation related to BRs.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.026195. 1 These authors contributed equally to this paper. 2 Present address: Department of Physiology and Quality Science, National Institute of Vegetables and Tea Science, National Agricultural Research Organization, 360 Kusawa, Ano, Mie 514–2392, Japan * Corresponding author; e-mail mchono{at}affrc.go.jp; fax 81–29–838–8870. Received May 6, 2003; returned for revision June 18, 2003; accepted August 13, 2003. This article has been cited by other articles:
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