Overexpression of Na+/H+ antiporter gene AtNHX1 from Arabidopsis thaliana improves the salt tolerance of kiwifruit (Actinidia deliciosa)

Salinity is the main limiting factor of plant growth and agricultural productivity. A lot of previous works showed that the introduction of Na+/H+ antiporter gene could improve the tolerance of plants to salt. In this study, a vacuolar Na+/H+ antiporter gene, AtNHX1 from Arobidopsis, was transferred into kiwifruit by Agrobacterium-mediated protocol. Polymerase chain reaction (PCR) and Southern blot analysis confirmed that AtNHX1 was successfully integrated into the kiwifruit genome. Reverse transcription (RT)-PCR analysis indicated that AtNHX1 expressed highly in transgenic plants. It was found that transgenic kiwifruit plants exhibited improved resistance to 200 mmol/l NaCl in comparison with wide-type plants. Under salt stress, these transgenic lines accumulated more Na+ than control, due to an increased Na+/H+ antiporter activity. In physiological analysis, the traits such as osmotic adjustment and antioxidation capability of transgenic lines under salt stress were obviously higher than that of wide-type plants. These results suggested that the overexpression of vacuolar Na+/H+ antiporter gene could increase the salt tolerance of kiwifruit.

Research Highlights
► Agrobacterium-mediated protocol was an effectual approach for Actinidia deliciosa.
► AtNHX1 was successfully integrated into the kiwifruit genome and expressed highly.
► Overexpression of AtNHX1 improved salt-tolerance and growth of transgenic kiwifruit.
► Transgenic kiwifruit had better osmotic adjustment and higher antioxidant capacity.