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Downregulation of high-affinity potassium and sodium symporter gene, EcHKT1;1, in Eucalyptus roots enhances salt tolerance
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  • BALASUBRAMANIAN Aiyar,
  • Selvakesavan Rajendran kamalabai,
  • Shamili Krishnaraj,
  • Sandhya M C,
  • Usha Jayachandran,
  • Sudha Selvam,
  • Siva kumar V,
  • Sowmiya Kottaipalayam-Somasundaram,
  • Suryaprabha A C,
  • Vijaya Kumar Waman Bachpai,
  • Hassen Gherbi,
  • Claudine Franche,
  • Mathish Nambiar-Veetil
BALASUBRAMANIAN Aiyar
Institute of Forest Genetics and Tree Breeding
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Selvakesavan Rajendran kamalabai
Institute of Forest Genetics and Tree Breeding
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Shamili Krishnaraj
Institute of Forest Genetics and Tree Breeding
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Sandhya M C
Institute of Forest Genetics and Tree Breeding
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Usha Jayachandran
Institute of Forest Genetics and Tree Breeding
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Sudha Selvam
Institute of Forest Genetics and Tree Breeding
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Siva kumar V
Institute of Forest Genetics and Tree Breeding
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Sowmiya Kottaipalayam-Somasundaram
Institute of Forest Genetics and Tree Breeding
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Suryaprabha A C
Institute of Forest Genetics and Tree Breeding
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Vijaya Kumar Waman Bachpai
Institute of Forest Genetics and Tree Breeding
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Hassen Gherbi
French National Research Institute for Sustainable Development
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Claudine Franche
French National Research Institute for Sustainable Development
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Mathish Nambiar-Veetil
Institute of Forest Genetics and Tree Breeding
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Abstract

Engineering for restricted root Na+ uptake could potentially enhance salt tolerance in Eucalyptus. High-affinity K+ transporters (HKTs) have been implicated in Na+ uptake from the external medium as in the case of TaHKT2;1 or in the unloading of Na+ from xylem like in AtHKT1;1. To rapidly determine the in planta role of EcHKT1:1, composite transgenics in which EcHKT1:1 was specifically downregulated via RNAi in the roots were generated. Compared to the controls that failed to survive at 350 mM NaCl, 33 % of the composite transgenic plantlets generated using the EcHKT1;1 silencing construct were able to tolerate up to 400 mM NaCl. In these composite transgenics, EcHKT1;1 downregulation ranged from 37 % to 74 %. The average shoot to root ratio of sodium was 4.9 folds lower than the controls indicating restricted translocation of Na+ to the shoots. Relative expression analysis in the leaves of two non-transgenic genotypes contrasting for their salt tolerance also showed downregulated EcHKT1;1 expression in the tolerant clone. The study thus determined that EcHKT1;1 is a major gene determining Na+ transport from the roots to shoots. This study also demonstrated the utility of the composite transgenic approach for screening genes conferring salt tolerance in tree species.