Ectopic expression of SbNHX1 gene in transgenic castor (Ricinus communis L.) enhances salt stress by modulating physiological process

Abstract

The SbNHX1 gene encodes a vacuolar Na⁺/H⁺ antiporter that involved in the maintenance of ion homeostasis and compartmentalization of excess Na⁺ or K⁺ ions into the vacuole. Transgenic castor plants were developed by an improved method of Agrobacterium mediated genetic transformation using spermidine (1 mM) along with acetosyringone (200 μM), which enhanced the transformation efficiency about twofolds from 2.76 to 5.91 %. Transgenic plants were confirmed by PCR using gene (SbNHX1, hptII and gus) specific primers. The single gene integration event was confirmed by RTqPCR and Southern hybridization. Transgenic lines CL7 and CL13 showed high expression of the SbNHX1 gene compared to CL6 and CL12, therefore selected for physio-biochemical analyses, which were carried out under varying NaCl concentrations. Higher chlorophyll, RWC, K⁺ content, K⁺/Na⁺ ratio and lower electrolytic leakage, proline, MDA, Na⁺ contents compared to WT confirmed that ectopic expression of the SbNHX1 gene enhances salt tolerance of transgenic plants by modulating physiological process under stress condition. Though transgenic lines were affected under stress conditions but performed better compared to WT plants. The present study is the first report of engineering salt tolerance in castor, so far. Transgenic castor may be utilized for the cultivation in marginal salty land and thus open up the possibility of releasing arable land, which is presently under castor cultivation.