Improved salinity tolerance and growth performance in transgenic sunflower plants via ectopic expression of a wheat antiporter gene (TaNHX2)
Sunflower (Helianthus annuus. L) is one of the principal oil seed crops affected by the salinity stress, which limits the oil content and crop yield of sunflower plants. The acclimatization of plants to abiotic stresses such as salinity tolerance is mainly mediated by the vacuolar Na+/H+ antiporters (NHX) by tagging Na+ into vacuoles from the cytosol. We show here that the over-expression of wheat TaNHX2 gene in transgenic sunflower conferred improved salinity stress tolerance and growth performance. Transgenic sunflower plants were produced by infecting the embryonic axis ex-plants with Agrobacterium tumefaciens strain EHA105 containing a pBin438-TaNHX2 binary vector that carried a wheat antiporter (TaNHX2) gene under the control of a double CaMV 35S promoter with NPT II gene as a selectable marker. PCR analysis of T0 and T1 transgenic plants confirmed the integration of TaNHX2 in sunflower genome. Stable integration and expression of TaNHX2 in sunflower genome was further verified by Southern hybridization and semi-quantitative RT-PCR analyses. As compared to the non-transformed plants, TaNHX2 expressing transgenic plants showed better growth performance and accumulated higher Na+, K+ contents in leaves and roots under salt stress (200 mM NaCl). Transgenic sunflower plants displayed improved protection against cell damage exhibiting stable relative water content, chlorophyll content, increased proline accumulation and improved reactive oxygen species (ROS) scavenging because of higher activities of the antioxidant enzymes like superoxide dismutase and ascorbate peroxidase, along with decreased production of hydrogen peroxide, free oxygen radical and malondialdehyde (MDA) under salt stress (200 mM NaCl). Taken together, our findings suggest that TaNHX2 expression in sunflower plants contributed towards improving growth performance under sodium chloride stress.
KeywordsTaNHX2 Sunflower Helianthus annuus Salt stress Antioxidant enzymes ROS scavenging
Reverse transcription polymerase chain reaction
Relative water content
Reactive oxygen species
Fully turgid weight
The authors acknowledge the Head, Department of Plant Sciences, University of Hyderabad for access to the research facilities provided by DST-FIST, DBT-CREBB, and UGC-SAP in undertaking this investigation. Authors also thank Prof.Souyi Chen and Jinsong Zhang, Institute of Genetics and Developmental Biology, CAS, Beijing for providing the pBin438-TaNHX2 construct. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
RY and PBK conceived the experiments. RM and RY performed the experiments. RM, RY, and PBK analyzed the data. RY and PBK wrote the manuscript. All authors approved the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that there are no conflicts of interest.
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