Overexpression of a Chimeric Gene, OsDST-SRDX, Improved Salt Tolerance of Perennial Ryegrass

The Drought and Salt Tolerance gene (DST) encodes a C(2)H(2) zinc finger transcription factor, which negatively regulates salt tolerance in rice (Oryza sativa). Phylogenetic analysis of six homologues of DST genes in different plant species revealed that DST genes were conserved evolutionarily. Here, the rice DST gene was linked to an SRDX domain for gene expression repression based on the Chimeric REpressor gene-Silencing Technology (CRES-T) to make a chimeric gene (OsDST-SRDX) construct and introduced into perennial ryegrass by Agrobacterium-mediated transformation. Integration and expression of the OsDST-SRDX in transgenic plants were tested by PCR and RT-PCR, respectively. Transgenic lines overexpressing the OsDST-SRDX fusion gene showed obvious phenotypic differences and clear resistance to salt-shock and to continuous salt stresses compared to non-transgenic plants. Physiological analyses including relative leaf water content, electrolyte leakage, proline content, malondialdehyde (MDA) content, H(2)O(2) content and sodium and potassium accumulation indicated that the OsDST-SRDX fusion gene enhanced salt tolerance in transgenic perennial ryegrass by altering a wide range of physiological responses. To our best knowledge this study is the first report of utilizing Chimeric Repressor gene-Silencing Technology (CRES-T) in turfgrass and forage species for salt-tolerance improvement.