Brachytic 1 of barley (Hordeum vulgare L.) encodes the α subunit of heterotrimeric G protein

Physiological and molecular biological analysis of the dwarf barley (Hordeum vulgare L.) mutant brachytic 1 (brh1) was conducted. The root responses of brh1 to brassinolide were weaker than those of wild type, but the responses of leaf segments of dark-grown plants were not. Responses of brh1 to gibberellin A(3) were similar to or slightly stronger than those of wild type. Endogenous levels of these hormones in young seedlings were not clearly different between brh1 and wild type. Skotomorphogeneses of brh1 were similar to those of wild type. Some of these physiological characteristics of brh1 resemble those of the dwarf rice (Oryza sativa L.) mutant daikoku (dwarf1; d1), whose dwarfism is caused by a mutation in the heterotrimeric G protein a (G alpha) subunit. A database search indicated that the barley G alpha gene is located near the locus where Brh1 has already been genetically mapped. Sequences of the G alpha gene and cDNAs of five brh1 alleles contained substitutions and a deletion that lead to the production of abnormal Ga proteins. These results indicate that the phenotype of brh1, similarly to that of d1, is caused by mutations in an orthologous gene encoding G alpha.