title: Modification of gibberellin signalling (metabolism & signal transduction) in sugar beet: analysis of potential targets for crop improvement.
abstract: Sugar beet, Beta vulgaris spp. vulgaris is a biennial long day plant with an obligate requirement for vernalization (prolonged exposure to low temperature). As a spring crop in temperate European climates, it is vulnerable to vernalization-induced premature bolting and flowering, resulting in reduced crop yield and quality. Gibberellins (GAs) play important roles in key physiological processes including stem elongation (bolting) and flowering and are, therefore, potential targets for controlling reproductive growth in sugar beet. We show that the BvGA20ox gene, which encodes an enzyme necessary for GA biosynthesis, was transcriptionally activated in apices of sugar beet plants after vernalization and that GA metabolism can be manipulated to delay bolting in vernalized plants. We demonstrate that down-regulation of GA responses by transformation with the Arabidopsis thaliana gai gene (which represses GA signalling), under its own promoter (pgai::gai) or deactivation of GA by over-expression of the Phaseolus coccineus (bean) GA2ox1 gene, which inactivates GA, increased the required post vernalization thermal time (an accurate and stable measure of physiological time), to bolt by approximately 300 degrees Cd. This resulted in agronomically significant bolting time delays of approximately 2 weeks and 3 weeks in the pgai::gai and 35S::PcGA2ox1 plants, respectively. Our data represent the first transgenic sugar beet model to (1) show that GA signalling can be used to improve crops by manipulation of the transition to reproductive growth; and (2) provide evidence that GA is required for seed set in sugar beet.
authors.affiliation: Broom's Barn Research Station, Higham, Bury St. Edmunds, Suffolk IP28 6NP, UK. effie.mutasa@bbsrc.ac.uk
authors.forename: Effie
authors.initials: E
authors.lastname: Mutasa-Gottgens
authors.forename: Aiming
authors.initials: A
authors.lastname: Qi
authors.forename: Ann
authors.initials: A
authors.lastname: Mathews
authors.forename: Stephen
authors.initials: S
authors.lastname: Thomas
authors.forename: Andrew
authors.initials: A
authors.lastname: Phillips
authors.forename: Peter
authors.initials: P
authors.lastname: Hedden
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D027461:Beta vulgaris / Q000235:genetics* / Q000378:metabolism*; D018556:Crops, Agricultural / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005821:Genetic Techniques; D005875:Gibberellins / Q000378:metabolism*; D008027:Light; D008957:Models, Genetic; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; D010940:Plant Proteins