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Transgenic salt-tolerant sugar beet (Beta vulgaris L.) constitutively expressing an Arabidopsis thaliana vacuolar Na+/H+ antiporter gene, AtNHX3, accumulates more soluble sugar but less salt in storage roots

Authors

  • HUA LIU,

    1. National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China and
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  • QIUQING WANG,

    1. National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China and
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  • MENGMENG YU,

    1. National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China and
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  • YANYAN ZHANG,

    1. College of Life Science, Nanjing Agricultural University, Nanjing 210095, China
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  • YINGBAO WU,

    1. College of Life Science, Nanjing Agricultural University, Nanjing 210095, China
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  • HONGXIA ZHANG

    Corresponding author
    1. National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China and
      H. Zhang. Fax: 86 21 54924015; e-mail: hxzhang@sippe.ac.cn
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H. Zhang. Fax: 86 21 54924015; e-mail: hxzhang@sippe.ac.cn

ABSTRACT

In Arabidopsis thaliana, six vacuolar Na+/H+ antiporters (AtNHX1-6) were identified. Among them, AtNHX1, 2 and 5 are functional Na+/H+ antiporters with the most abundant expression levels in seedling shoots and roots. However, the expression of AtNHX3 in Arabidopsis can only be detected by RT-PCR, and its physiological function still remains unclear. In this work, we demonstrate that constitutive expression of AtNHX3 in sugar beet (Beta vulgaris L.) conferred augmented resistance to high salinity on transgenic plants. In the presence of 300 or 500 mm NaCl, transgenic plants showed very high potassium accumulation in the roots and storage roots. Furthermore, the transcripts of sucrose phosphate synthase (SPS), sucrose synthase (SS) and cell wall sucrose invertase (SI) genes were maintained in transgenic plants. The accumulation of soluble sugar in the storage roots of transgenic plants grown under high salt stress condition was also higher. Our results implicate that AtNHX3 is also a functional antiporter responsible for salt tolerance by mediating K+/H+ exchange in higher plants. The salt accumulation in leaves but not in the storage roots, and the increased yield of storage roots with enhanced constituent soluble sugar contents under salt stress condition demonstrate a great potential use of this gene in improving the quality and yield of crop plants.

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