Pea DNA helicase 45 overexpression in tobacco confers high salinity tolerance without affecting yield

Abstract

Salt tolerance is an important trait that is required to overcome salinity-induced reduction in plant productivity. We have reported previously the isolation of a pea DNA helicase 45 (PDH45) that exhibits striking homology with the eukaryotic translation initiation factor eIF-4A. Here, we report that PDH45 mRNA is induced in pea seedlings in response to high salt, and its overexpression driven by a constitutive cauliflower mosaic virus-³⁵S promoter in tobacco plants confers salinity tolerance, thus suggesting a previously undescribed pathway for manipulating stress tolerance in crop plants. The T₀ transgenic plants showed high levels of PDH45 protein in normal and stress conditions, as compared with WT plants. The T₀ transgenics also showed tolerance to high salinity as tested by a leaf disk senescence assay. The T₁ transgenics were able to grow to maturity and set normal viable seeds under continuous salinity stress without any reduction in plant yield in terms of seed weight. Measurement of Na⁺ ions in different parts of the plant showed higher accumulation in the old leaves and negligible accumulation in seeds of T₁ transgenic lines as compared with the WT plants. The possible mechanism of salinity tolerance is discussed. Overexpression of PDH45 provides a possible example of the exploitation of DNA/RNA unwinding pathways for engineering salinity tolerance without affecting yield in crop plants.