OVEREXPRESSION OF OSNAC6 TRANSCRIPTION FACTOR FROM INDONESIA RICE CULTIVAR ENHANCES DROUGHT AND SALT TOLERANCE

Abstract

Drought is a major constrain in crop production that reduce growth and cause yield loss of up to 70%. Transcription factor plays a major role in cellular regulation and physical changes of plants as a response to stress. A number of transcription factors, such as CBF/DREB, NAC, zinc finger protein are regulators during stress. The Oryza sativa NAC6 (OsNAC6) gene is one of the transcription factor in rice that can regulate gene expression during stress conditions. Thus, pCambia 1305 harboring OsNAC6 chimaeric gene with CaMV 35S promoter was introduced into rice zygotic embryo using Agrobacterium tumefaciens mediated transformation to regenerate transgenic rice overexpressing the transgene. As many as 39 putative transgenic lines in which 21 lines possitively harbored hpt gene have been regenerated. The positive identification of hpt in the regenerated transgenic rice indirectly indicated integration of the targeted OsNAC6 since both transgenes were part of the same T-DNA. Further analysis indicated the presence of 1-3 copies of transgene integration in the genome. The expression of OsNAC6 transgene in the transgenic rice line#C.73, C.83 and C.91 were higher than wild type non-transgenic one. Further analysis indicated those three transgenic lines carrying OsNAC6 transgene exhibited higher tolerance against drought and salinity stresses. Moreover, three known stress-associated regulatory genes (AP2, Zincfinger protein and MYB) were up-regulated in those three transgenic lines. These findings demonstrated that OsNAC6 might be a candidate of stress-responsive NAC regulatory gene that can be used to develop either drought or salt tolerant tolerant transgenic plants.