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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

Molecular and Functional Characterization of PEBP Genes in Barley Reveal the Diversification of Their Roles in Flowering^1,[W],[OA]

Plant Genome Research Unit, National Institute of Agrobiological Sciences, Tsukuba 305–8602, Japan (R.K., H.K., H.H.); Institute of the Society for Techno-innovation of Agriculture, Forestry, and Fisheries, Tsukuba 305–0854, Japan (T.A.); Barley Research Subteam, National Institute of Crop Science, Tsukuba 305–8518, Japan (T.T.); and Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305–8572, Japan (H.H.)

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. HvFT3 was mapped to chromosome 1HL, the same chromosome that carries Ppd-H2. Genomic sequence analyses revealed that Morex possesses an intact HvFT3 gene, whereas most of this gene has been lost in Steptoe. These data strongly suggest that HvFT3 may be identical to Ppd-H2.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Hirokazu Handa (hirokazu{at}affrc.go.jp).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.132134

^* Corresponding author; e-mail hirokazu{at}affrc.go.jp.

Received November 4, 2008; accepted January 21, 2009; published January 23, 2009.

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