Heterologous expression of banana MaDREB16 gene in Arabidopsis increases tolerance to dehydration and combined dehydration plus heat stress through stomatal regulation and root elongation

We report here isolation of a dehydration responsive element binding 2 ( DREB2 ) gene ( MaDREB16 ) from Grand Nain (GN) cultivar of Musa acuminata and its involvement in dehydration and heat stress responses in transgenic Arabidopsis plant. Expression analysis of MaDREB16 in root tissues of two banana varieties showed its significant expression under dehydration and combined dehydration plus heat stress. Our findings demonstrate that soil grown transgenic Arabidopsis plants overexpressing MaDREB16 gene display better rate of survival, aerial dry biomass, seed production, relative water content and content of free proline, whereas it has lower ion leakage and malondialdehyde content under the stress conditions studied. Transgenic Arabidopsis plants also showed significant induction of downstream marker genes under dehydration, heat as well as their combination of stresses. Transgenic Arabidopsis displayed reduced stomatal densities and indices even under unstressed conditions suggesting that the transgene modifies the stomatal characteristics and improved regulation of stomatal aperture in dehydration stress as compared to wild-type Arabidopsis. These alterations may be accountable for the observed improved tolerance against individual and combined stress studied.in transgenic as compared to the wild-type. Interestingly the transgenic Arabidopsis showed improved germination rate and root growth under mannitol and combined mannitol plus heat stresses. Altogether, our findings reveal that the MaDREB16 is an important gene of attention to exploit in transgenic breeding to augment tolerance in not only banana against dehydration and its combination with heat stress but also in other crops.