Ectopic expression of an oat SnRK2 gene, AsSnRK2D, enhances dehydration and salinity tolerance in tobacco by modulating the expression of stress-related genes

Abstract

SnRK2 protein kinases have been demonstrated to have an important effect on the physiological processes of plant stress tolerance. Here, one of the SnRK2 family members, designated AsSnRK2D, was isolated from oat (Avena sativa Linn. L.). The AsSnRK2D protein includes functional domains specific to the SnRK2 family. The AsSnRK2D protein and its 12 and 21 counterparts were classified into Group II and SnRK2a, respectively. The AsSnRK2D gene was constitutively expressed and positively responded to abscisic acid, low-temperature, salt, and dehydration stress. The subcellular localization analysis revealed that the AsSnRK2.7 protein was localized primarily in the nucleus. Ectopic expression of the AsSnRK2D gene in tobacco resulted in an improvement in the primary root length and plant fresh weight under dehydration and salt stress. The AsSnRK2D-overexpressing tobacco demonstrated improved tolerance to stress resulting from dehydration and salinity, as supported by the morphological changes, survival rates, and physiological indices, including electrolyte leakage, superoxide dismutase level, catalase activity, chlorophyll yield, relative water content, accumulation of reactive oxygen species such as superoxide anion radical and hydrogen peroxide, and the level of free proline. The AsSnRK2D gene was associated with the stress responses of the transgenic tobacco to dehydration and salinity via the regulation of a series of stress-inducible genes, including dehydrins (NtERD10B, NtERD10D, and NtLEA5), cell signaling components (NtPLC3 and NtCaMK1), transcription factors (NtDREB2 and NtDREB4), antioxidative enzymes (NtMnSOD and NtCAT), and proline biosynthesis (NtP5CS). The results show that the AsSnRK2D gene has certain application potential in improving crop tolerances to dehydration and salinity stress.