Expression of the alfalfa gene MsMDHAR in Arabidopsis thaliana increases water stress tolerance.

The ascorbate-glutathione pathway plays an essential role in the physiology of vascular plants, particularly in their response to environmental stresses. This pathway is responsible for regulating the cellular redox state, which is critical for maintaining cell function and survival under adverse conditions. To study the involvement of the alfalfa monodehydroascorbate reductase (MsMDHAR) in water stress processes, Arabidopsis thaliana plants constitutively expressing the sequence encoding MsMDHAR were developed. Transgenic events with low and high MsMDHAR expression and ascorbate levels were selected for further analysis of drought and waterlogging tolerance. Under water stress, Arabidopsis transgenic plants generated higher biomass, produced more seeds, and had larger roots than wild type ones. This higher tolerance was associated with increased production of waxes and chlorophyll a at the basal level, greater stomatal opening and stability in regulating the relative water content and reduced H₂O₂ accumulation under stress conditions in transgenic plants. Overall, these results show that MsMDHAR is involved in plant tolerance to abiotic stresses. The data presented here also emphasises the potential of the MsMDHAR enzyme as a plant breeding tool to improve water stress tolerance.