Overexpression of Wheat DREB3 Transcription Factor in Barley Improves Stress Tolerance and Changes Small RNA Expression Pattern

Transcription factors (TFs) are key players in all organisms, regulating gene expression in response to environmental changes. Increased understanding of the involvement of TFs in controlling abiotic stress responses has lead to practical approaches for engineering plants tolerant to abiotic stresses. In this study, we isolated a dehydration responsive element binding (DREB) TF (TaDREB3) from wheat and over-expressed it in barley (Golden Promise). Transgenic barley displayed slower growth, delayed flowering and lower grain yields, but strong tolerance to cold and drought stresses, compared to non-transgenic barley. Seven CBF/DREB genes (HvCBF1, HvCBF3, HvCBF6, HvCBF10A, HvCBF11, HvCBF15 and HvCBF16) increased, while three other CBF/DREB genes (HvCBF2, HvCBF9 and HvCBF14) decreased in expression level in transgenic barley. Over-expressed TaDREB3 also affected the expression of stress-responsive LEA/COR/DHN genes that protect cells from damage and desiccation under stress. We also investigated effects of over-expressed TaDREB3 on the expression of small RNAs (sRNAs) including microRNAs (miRNAs), which are another important class of gene regulators. We observed great changes in the expression of miRNAs and other functional non-coding sRNAs in transgenic barley. About half of the common sRNAs were differentially expressed between transgenic barley and non-transgenic barley. In addition, sRNAs derived from TaDREB3 were only detected in transgenic barley, but not in non-transgenic barley. These data indicate that TaDREB3 regulates the expression of sRNAs, and that sRNAs may in turn regulate TaDREB3. Our study provides the foundations for a novel means to further improve plant tolerance to abiotic stresses, through the manipulation of both TFs and sRNAs.