Functional Plant Biology Functional Plant Biology Society
Plant function and evolutionary biology
RESEARCH ARTICLE

The vacuolar Na+–H+ antiport gene TaNHX2 confers salt tolerance on transgenic alfalfa (Medicago sativa)

Yan-Min Zhang A B , Zi-Hui Liu A , Zhi-Yu Wen A , Hong-Mei Zhang A , Fan Yang A and Xiu-Lin Guo A B

A Institute of Genetics and Physiology, Hebei Academy of Agriculture and Forestry Sciences, Plant Genetic Engineering Center of Hebei Province, Shijiazhuang 050051, China.

B Corresponding author. Emails: zhym63@sohu.com; myhf2002@yahoo.com.cn

Functional Plant Biology 39(8) 708-716 http://dx.doi.org/10.1071/FP12095
Submitted: 15 December 2011  Accepted: 6 June 2012   Published: 18 July 2012

Abstract

TaNHX2, a vacuolar Na+–H+ antiport gene from wheat (Triticum aestivum L.), was transformed into alfalfa (Medicago sativa L.) via Agrobacterium-mediated transformation to evaluate the role of vacuolar energy providers in plant salt stress responses. PCR and Southern blotting analysis showed that the target gene was integrated into the Medicago genome. Reverse transcription–PCR indicated that gene TaNHX2 was expressed at the transcriptional level. The relative electrical conductivity in the T2 transgenic plants was lower and the osmotic potential was higher compared to the wild-type plants under salt stress conditions. The tonoplast H+-ATPase, H+-pyrophosphatase (PPase) hydrolysis activities and ATP-dependent proton pump activities in transgenic plants were all higher than those of wild-type plants, and the enzyme activities could be induced by salt stress. The PPi-dependent proton pump activities decreased when NaCl concentrations increased from 100 mM to 200 mM, especially in transgenic plants. The vacuolar Na+–H+ antiport activities of transgenic plants were 2–3 times higher than those of the wild -type plants under 0 mM and 100 mM NaCl stress. Na+–H+ antiport activity was not detectable for wild-type plants under 200 mM NaCl, but for transgenic plants, it was further increased with an increment in salt stress intensity. These results demonstrated that expression of the foreign TaNHX2 gene enhanced salt tolerance in transgenic alfalfa.

Additional keywords: H+-ATPase, H+-PPase, pump activity, salt stress.


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