Characterization of Dehydrin Sugarcane Gene and its Role in Drought Tolerance through Heterologous Expression in Rice

Currently, drought tolerance is one of the main focus in the development of transgenic sugarcane cultivars. However, the lack of well-characterized genes to be used as target corresponds to the main bottleneck on the generation of transgenic cultivars from a commercial standpoint. In order to understand the mechanisms of drought response in sugarcane, dehydrin (DHN) gene was selected as candidate for functional analysis in rice, a model plant for monocots. The DHN sequence gene was successfully isolated using RACE methodology, and overexpression vector was obtained by gateway multi-recombination carrying the ubiquitin promoter and hygromycin phosphotransferase gene as selectable marker. The relative expression of transgene was evaluated by the 2^-ΔCt method, and T-DNA copy number were obtained by Taqman^® assay using hptII gene. A total of four transgenic lines, with a single copy T-DNA insertion, showing different expression levels of the target gene, were cultivated at greenhouse and subjected to water restriction for morphological evaluations. DHN#81 and DHN#19 lines showed a decrease of growth under well watering and water deficit conditions when compared to wild-type plants. DHN#12 line exhibited a decrease of growth under well watering conditions, but showed increase in dry weight of roots under water deficit. DHN#4 line did not show morphological statistical differences when compared to wild-type plants. In general, the morphological parameters were elucitative to reveal the contribution of the gene here evaluated to drought tolerance. Therefore, based on these results, the overexpression of DHN gene did not contributed to increase the performance of rice transgenic plants under water restricted conditions.