Comparative analysis of heterologous expressions of BADH and Fld genes in enhancing salinity and drought tolerance of the ajowan medicinal plant

Key Message The heterologous expression of BADH and Fld transgenes was compared in ajowan medicinal plant. The antioxidant activities, glycine betaine and proline contents of transgenic lines were higher than wild types. BADH was superior to Fld in enhancing stress tolerance of ajowan. We conducted a comparative analysis of the effects of two key stress-tolerance genes, spinach betaine aldehyde dehydrogenase (BADH) and cyanobacterial flavodoxin (Fld), on enzymatic, non-enzymatic antioxidants, content of glycine betaine (GB) and proline osmo-protectants and relative water content (RWC) of ajowan (Trachyspermum ammi L.) transgenic lines (obtained previously by Agrobacterium-mediated transformation) under in vitro and greenhouse salinity and drought stress. The heterologous expressions of BADH and Fld genes significantly enhanced salinity and drought tolerance of ajowan transgenic lines in comparison with wild-type plants. BADH- and Fld-overexpressing ajowan plants (TaBADH and TaFld) showed higher activity of catalase, peroxidase and superoxide dismutase enzymatic antioxidants under in vitro salinity and drought conditions. Compared with wild-type plants, TaBADH and TaFld lines had higher accumulation of GB and proline osmo-protectants under in vitro salinity and drought stress. During the water-stress experiment in greenhouse conditions, TaBADH and TaFld ajowan plants showed significantly higher RWC than their non-transformed counterparts. Results of both in vitro and greenhouse assessments reported the superiority of BADH over Fld in enhancing salinity and drought stress tolerance in ajowan plants. Further experiments are required to accurately demonstrate the superiority of each of these two genes over the other. The co-delivery of BADH and Fld transgenes would be more effective than their individual heterologous expressions, as there two genes affect the stress response of plants through different mechanisms.