Overexpression of a Malus vacuolar Na+/H+ antiporter gene (MdNHX1) in apple rootstock M.26 and its influence on salt tolerance

摘要

Soil salinity is a major factor limiting apple production in some areas. Tonoplast Na+/H+ antiporters play a critical role in salt tolerance. Here, we isolated MdNHX1, a vacuolar Na+/H+ antiporter from Luo-2, a salt-tolerant rootstock of apple (Malus × domestica Borkh.), and introduced it into apple rootstock M.26 by Agrobacterium-mediated transformation. PCR and DNA gel blot analyses confirmed successful integration of MdNHX1. RT-PCR analysis indicated that the gene was highly expressed in transgenic plants, but the degree of this expression varied among lines. Its overexpression conferred high tolerance to salt stress. Analysis of ion contents showed that, when exposed to salinity stress, the transgenics compartmentalized more Na+ in the roots and also maintained a relatively high K+/Na+ ratio in the leaves compared with non-transformed plants. Under normal conditions, however, amounts of potassium and sodium did not differ significantly between transgenic and control plants.