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Constitutive expression of a fruit phytoene synthase gene in transgenic tomatoes causes dwarfism by redirecting metabolites from the gibberellin pathway

Authors

  • Rupert G. Fray,

    1. BBSRC Research Group in Plant Gene Regulation, Department of Physiology and Environmental Science, Nottingham University, Sutton Bonington Campus, Loughborough LE12 5RD, UK
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  • Andrew Wallace,

    1. BBSRC Research Group in Plant Gene Regulation, Department of Physiology and Environmental Science, Nottingham University, Sutton Bonington Campus, Loughborough LE12 5RD, UK
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  • Paul D. Fraser,

    1. Department of Biochemistry, Royal Holloway and Bedford New College, University of London, Egham, Surrey TW20 0EX, UK
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  • Daniel Valero,

    1. IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS18 9AF, UK
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  • Peter Hedden,

    1. IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS18 9AF, UK
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  • Peter M. Bramley,

    1. Department of Biochemistry, Royal Holloway and Bedford New College, University of London, Egham, Surrey TW20 0EX, UK
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  • Donald Grierson

    Corresponding author
    1. BBSRC Research Group in Plant Gene Regulation, Department of Physiology and Environmental Science, Nottingham University, Sutton Bonington Campus, Loughborough LE12 5RD, UK
      *For correspondence (fax +44 115 951 6334).
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*For correspondence (fax +44 115 951 6334).

Abstract

Tomato plants transformed with a copy of the fruit-expressed phytoene synthase cDNA under control of the CaMV 35S promoter showed ectopic production of carotenoids. High expressers were reduced in stature. The dwarf character was inherited with an inverse relationship between expression of phytoene synthase and plant height. Severely affected plants also showed reduced chlorophyll content in young leaves. These dwarfs showed a 30-fold reduction in levels of gibberellin A1 (GA1) and growth was partially restored by treatment with exogenous GA3. Qualitative and quantitative changes in carotenoids were also found. It is proposed that the dwarf phenotype results from the over-production of phytoene synthase, which converts geranylgeranyl diphosphate to phytoene and thereby diverts this intermediate away from the gibberellin (GA) and phytol biosynthetic pathways.

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