Over-expressing Salicornia europaea (SeNHX1) gene in tobacco improves tolerance to salt
Vacuolar Na+/H+ antiporters provide an efficient mechanism to avert the deleterious effects of Na+ by its compartmentalization into vacuoles. In this study, SeNHX1, a vacuolar Na+/H+ antiporter from Salicornia europaea.L, was introduced into tobacco to investigate its response to salt tolerance, and to study how over-expression of this gene can affect other physiological responses. An increase of salt tolerance in transgenics was observed both in vitro and in pot culture. When exposed to either 138 mM or 172 mM NaCl in vitro, the transgenic apical meristem and stem segments with buds exhibited stronger salt-tolerance than their wild-type counterparts. In pot soil with 10.2 mg g-1 DW Na+ stress, transgenic plants over-expressing SeNHX1 accumulated 1.2 mg g-1 FW Na+ greater than wild type in old leaves. Meanwhile, no difference was observed in young leaves. Dry weight and height of transgenic plants were reduced less compared to that of wild type. Moreover, under high salt stress, the malondialdehyde (MDA) content in transgenic plants was significantly lower, but proline content and activity of antioxidant enzymes were obviously higher than that of wild-types. These results confirm and support the potential application of SeNHX1-transgenic plants for being cultivated in saline soil.
Key words: Antioxidant enzyme, MDA, Na+/H+ antiporter, Na+, proline.