Perennial ryegrass ( Lolium perenne L.) is an important cool-season grass in temperate regions worldwide. Salinity stress has become one of the major abiotic factors that severely affects plant growth. The area of saline land worldwide is nearly 1 billion hectares, and accounts for 10 percent of the total land area 1, 2. 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. Physiological analyses including relative leaf water content, electrolyte leakage, proline content, malondialdehyde (MDA) content, H 2O 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. 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. Integration and expression of the OsDST-SRDX in transgenic plants were tested by PCR and RT-PCR, respectively. 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. Phylogenetic analysis of six homologues of DST genes in different plant species revealed that DST genes were conserved evolutionarily. The Drought and Salt Tolerance gene ( DST) encodes a C 2H 2 zinc finger transcription factor, which negatively regulates salt tolerance in rice ( Oryza sativa).
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