THE BARLEY HOODED MUTATION CAUSED BY A DUPLICATION IN A HOMEOBOX GENEINTRON

IN barley (Hordeum vulgare L.) the unit of inflorescence is the spikel et, which bears a fertile bract, the lemma, and the floret consisting of palea, two lodicules, three stamens and the pistil(1). The Hooded m utation causes the appearance of an extra flower of inverse polarity o n the lemma(2). This phenotype is governed by the single dominant gene tic locus K-3 Here we show that the homeobox gene Knox3 represents thi s locus, Ectopic Knox3 gene expression in the primordium of the extra floret is caused by a 305-base pair duplication in inh on 4, and pheno copies of the mutation are obtained in the heterologous tobacco system by Knox3 overexpression. It is concluded that homeotic genes of the K nox gene family are involved in floral evocation. Furthermore, the stu dy of polarity of reproductive organs in K and related mutants can now focus on homeobox genes.