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Genetic engineering of glycinebetaine synthesis in tomato protects seeds, plants, and flowers from chilling damage

Authors

  • Eung-Jun Park,

    1. Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA, and
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  • Zoran Jeknić,

    1. Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA, and
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  • Atsushi Sakamoto,

    1. National Institute for Basic Biology, Okazaki 444-8585, Japan.
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    • Present address: Laboratory of Molecular Plant Biology, Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.

  • Jeanine DeNoma,

    1. Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA, and
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    • Present address: Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA.

  • Raweewan Yuwansiri,

    1. Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA, and
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  • Norio Murata,

    1. National Institute for Basic Biology, Okazaki 444-8585, Japan.
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  • Tony H. H. Chen

    Corresponding author
    1. Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA, and
      *(fax +541 737 3479; e-mail chent@science.oregonstate.edu).
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*(fax +541 737 3479; e-mail chent@science.oregonstate.edu).

Summary

Tomato (Lycopersicon esculentum Mill.) plants, which normally do not accumulate glycinebetaine (GB), are susceptible to chilling stress. Exposure to temperatures below 10°C causes various injuries and greatly decreases fruit set in most cultivars. We have transformed tomato (cv. Moneymaker) with a chloroplast-targeted codA gene of Arthrobacter globiformis, which encodes choline oxidase to catalyze the conversion of choline to GB. These transgenic plants express codA and synthesize choline oxidase, while accumulating GB in their leaves and reproductive organs up to 0.3 and 1.2 μmol g−1 fresh weight (FW), respectively. Their chloroplasts contain up to 86% of total leaf GB. Over various developmental phases, from seed germination to fruit production, these GB-accumulating plants are more tolerant of chilling stress than their wild-type counterparts. During reproduction, they yield, on average, 10–30% more fruit following chilling stress. Endogenous GB contents as low as 0.1 μmol g−1 FW are apparently sufficient to confer high levels of tolerance in tomato plants, as achieved via transformation with the codA gene. Exogenous application of either GB or H2O2 improves both chilling and oxidative tolerance concomitant with enhanced catalase activity. These moderately increased levels of H2O2 in codA transgenic plants, as a byproduct of choline oxidase-catalyzed GB synthesis, might activate the H2O2-inducible protective mechanism, resulting in improved chilling and oxidative tolerances in GB-accumulating codA transgenic plants. Thus, introducing the biosynthetic pathway of GB into tomato through metabolic engineering is an effective strategy for improving chilling tolerance.

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