Drought Screening and Physiological Characterization of Wheat Lines Transformed with DREB1A Gene Driven by RD29A Promoter.

Transcription factors are considered to be powerful tools for improving stress tolerance because they can regulate a large number of genes involved in complex physiological responses. Previous studies at the Japan International Research Centre for Agricultural Sciences (JIRCAS) have identified a family of transcription factors referred to as DREB (dehydration responsive element binding protein) genes, which promote the expression of genes contributing to a range of abiotic stress tolerances including drought tolerance. Pellegrineschi et al. (2004) inserted DREB1A from Arabidopsis thaliana, under the control of a stress inducible promoter from the rd29A gene, into the bread wheat line MPB Bobwhite 26, using biolistic-based transformation. Putative transformed plants were initially selected in the lab and glasshouse for expression of the marker gene (indicated by resistance to the herbicide Basta). Resistant plants were then tested for the presence of the DREB1A gene using PCR and Southern hybridization analyses.  Transformed plants that demonstrated tolerance to water stress under greenhouse conditions were selected. Further evaluations are being conducted on those transformed lines to confirm stress tolerance advantages and to determine additional effects on growth and productivity. The first step was to identify differential sensitivity to drought stress of different transgenic and control lines at different developmental stages. A second objective was to compare water use efficiency of transformed and untransformed lines. Transformation-events showed differences in their survival rate at the seven growth stages evaluated. Genotype ranking according to the survival rate changed from one growth stage to the other, probably as a result of differential gene expression across growth stages which could confer advantages in specific phenological phases. Preliminary results identified some events which may have better survival than non-transformed checks. Differences were also observed in phenology, biomass production, WUE, root index, and spike indexes.