title: FT overexpression induces precocious flowering and normal reproductive development in Eucalyptus.
abstract: Eucalyptus trees are among the most important species for industrial forestry worldwide. However, as with most forest trees, flowering does not begin for one to several years after planting which can limit the rate of conventional and molecular breeding. To speed flowering, we transformed a Eucalyptus grandis × urophylla hybrid (SP7) with a variety of constructs that enable overexpression of FLOWERING LOCUS T (FT). We found that FT expression led to very early flowering, with events showing floral buds within 1-5 months of transplanting to the glasshouse. The most rapid flowering was observed when the cauliflower mosaic virus 35S promoter was used to drive the Arabidopsis thaliana FT gene (AtFT). Early flowering was also observed with AtFT overexpression from a 409S ubiquitin promoter and under heat induction conditions with Populus trichocarpa FT1 (PtFT1) under control of a heat-shock promoter. Early flowering trees grew robustly, but exhibited a highly branched phenotype compared to the strong apical dominance of nonflowering transgenic and control trees. AtFT-induced flowers were morphologically normal and produced viable pollen grains and viable self- and cross-pollinated seeds. Many self-seedlings inherited AtFT and flowered early. FT overexpression-induced flowering in Eucalyptus may be a valuable means for accelerating breeding and genetic studies as the transgene can be easily segregated away in progeny, restoring normal growth and form.
authors.affiliation: Department Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Klocko
authors.affiliation: Department Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA.
authors.forename: Cathleen
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Robertson
authors.affiliation: Department Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA.
authors.forename: Elahe
authors.initials: E
authors.lastname: Esfandiari
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
authors.forename: Ove
authors.initials: O
authors.lastname: Nilsson
authors.affiliation: Department Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA.
authors.forename: Steven H
authors.initials: SH
authors.lastname: Strauss
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003433:Crosses, Genetic; D005052:Eucalyptus / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development*; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D018525:Germination; D010641:Phenotype; D010858:Pigmentation; D018515:Plant Leaves / Q000502:physiology; D030821:Plants, Genetically Modified; D011058:Pollen / Q000502:physiology; D054817:Pollination; D012098:Reproduction; D012639:Seeds / Q000502:physiology; D057945:Self-Fertilization; D014170:Transformation, Genetic
chemical_list: D029681:Arabidopsis Proteins; C418905:FT protein, Arabidopsis
keywords: Eucalypts; Flowering Locus T; breeding; forest biotechnology; genetic engineering; transgenic