Five barley (Hordeum vulgare) PEBP (for phosphatidylethanolamine-binding protein) genes were analyzed to clarify their functional roles in flowering using transgenic, expression, and quantitative trait locus analyses. Introduction of HvTFL1 and HvMFT1 into rice (Oryza sativa) plants did not result in any changes in flowering, suggesting that these two genes have functions distinct from flowering. Overexpression of HvFT1, HvFT2, and HvFT3 in rice resulted in early heading, indicating that these FT-like genes can act as promoters of the floral transition. HvFT1 transgenic plants showed the most robust flowering initiation. In barley, HvFT1 was expressed at the time of shoot meristem phase transition. These results suggest that HvFT1 is the key gene responsible for flowering in the barley FT-like gene family. HvFT2 transgenic plants also showed robust flowering initiation, but HvFT2 was expressed only under short-day (SD) conditions during the phase transition, suggesting that its role is limited to specific photoperiodic conditions in barley. Flowering activity in HvFT3 transgenic rice was not as strong and was modulated by the photoperiod. These results suggest that HvFT3 functions in flowering promotion but that its effect is indirect. HvFT3 expression was observed in Morex, a barley cultivar carrying a dominant allele of Ppd-H2, a major quantitative trait locus for flowering under SD conditions, although no expression was detected in Steptoe, a cultivar carrying ppd-H2. HvFT3 was expressed in Morex under both long-day and SD conditions, although its expression was increased under SD conditions.

(1,3;1,4)-β-D-glucans (mixed-linkage glucans) are found in tissues of members of the Poaceae (grasses), and are particularly high in barley (Hordeum vulgare) grains. The present study describes the isolation of three independent (1,3;1,4)-β-D-glucanless (betaglucanless; bgl) mutants of barley which completely lack (1,3;1,4)-β-D-glucan in all the tissues tested. The bgl phenotype cosegregates with the cellulose synthase like HvCslF6 gene on chromosome arm 7HL. Each of the bgl mutants has a single nucleotide substitution in the coding region of the HvCslF6 gene resulting in a change of a highly conserved amino acid residue of the HvCslF6 protein. Microsomal membranes isolated from developing endosperm of the bgl mutants lack detectable (1,3;1,4)-β-D-glucan synthase activity indicating that the HvCslF6 protein is inactive. This was confirmed by transient expression of the HvCslF6 cDNAs in Nicotiana benthamiana leaves. The wild-type HvCslF6 gene directed the synthesis of high levels of (1,3;1,4)-β-D-glucans, whereas the mutant HvCslF6 proteins completely lack the ability to synthesize (1,3;1,4)-β-D-glucans. The fine structure of the (1,3;1,4)-β-D-glucan produced in the tobacco leaf was also very different from that found in cereals having an extremely low DP3/DP4 ratio. These results demonstrate that, among the seven CslF and one CslH genes present in the barley genome, HvCslF6 has a unique role and is the key determinant controlling the biosynthesis of (1,3;1,4)-β-D-glucans. Natural allelic variation in the HvCslF6 gene was found predominantly within introns among 29 barley accessions studied. Genetic manipulation of the HvCslF6 gene could enable control of (1,3;1,4)-β-D-glucans in accordance with the purposes of use.

(1-3, 1-4)-β-D-glucan contained in barley (Hordeum vulgare L.) grains is a main component of endosperm cell walls and constitutes the cell wall matrix with arabinoxylan. A monofactorial recessive mutant gene for (1-3, 1-4)-β-D-glucanless grain was found and the new gene was designated as bgl (= (1-3, 1-4)-beta-Dglucanless grain). A linkage was found between the bgl gene and the naked caryopsis (nud) gene, and it was mapped to the centromeric region of chromosome 7H. Phenotypes in bgl cosegregated with the polymorphisms in HvCslF6, a member of cellulose synthase-like HvCslF gene family, indicating that bgl was caused by a mutation in the HvCslF6 locus. In order to clarify the characteristics of (1-3, 1-4)-β-D-glucanless barley grains, a near-isogenic line (NIL) was developed by backcrossing the Japanese two-rowed cultivar 'Nishinohoshi' as a recurrent parent. The NIL with bgl completely lacked (1-3, 1-4)-β-D-glucan in both the endosperm and aleurone layer cell walls. Microscopic analysis revealed that the NIL had thin endosperm cell walls. It also showed a softer grain texture and many more broken grains during the pearling process than the recurrent parent. The soft and friable grain texture of the NIL was probably caused by the thin endosperm cell walls.

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