Expression of a DREB 5-A subgroup transcription factor gene from Ricinus communis ( RcDREB1 ) enhanced growth, drought tolerance and pollen viability in tobacco

Climate change has increased the frequency of long periods of drought, affecting crop cultivation worldwide. Losses due to water stress exceed 10% of world production of major crops, reaching three-quarters of production areas, with severe economic losses. Therefore, the generation of environmental stress-tolerant genotypes that are more efficient in water use is extremely important. We have previously isolated and characterized a DREB transcription factor coding gene, named RcDREB1 , from castor bean ( Ricinus communis L.), which probably belongs to the CBF/DREB subfamily subgroup A-5. Aiming to develop drought-tolerant lines, we have stably introduced and expressed the RcDREB1 transgene into tobacco. Transgenic lines have revealed an enhanced drought tolerance. Genetically modified lines cultivated under water deficit presented a higher photosynthetic rate, stomatal conductance, leaf water potential and leaf water content when compared to the control. Transgenic lines revealed lower transpiration rates. In addition, biometric analyses showed that transgenic lines cultivated under water stress presented higher biomass, higher fresh and dry weight and higher plant height than the non-transgenic lines. After re-watering, transgenic lines recovered faster than non-transgenic plants. Moreover, pollen grains from transgenic plants revealed a remarkable increase in viability after exposure to heat (38 °C) and desiccation stresses. The results presented here will be the foundation for production of commercial crops that are more tolerant to environmental stresses and long-life pollen grains, increasing pollination and in consequence, productivity.