Ectopic expression of safflower NAC transcription factor CtNAC78 enhances drought tolerance in Arabidopsis thaliana

Drought has become a key abiotic stress factor that seriously affects crop yield, including that of safflower, an important crop grown worldwide. Our previous work showed that drought stress markedly upregulated CtNAC78 expression in safflower. Hence, to investigate CtNAC78's function in drought tolerance, transgenic Arabidopsis thaliana with ectopic expression of CtNAC78 was treated with drought in the present work. It was shown that the transgenic A. thaliana exhibited better growth status, higher antioxidant enzyme activity, greater accumulation of chlorophyll and osmolytes, and lower levels of MDA and H₂O₂, indicating that ectopic expression of CtNAC78 enhanced drought tolerance of A. thaliana. Furthermore, a yeast two-hybrid cDNA library was constructed from drought stress-treated safflower. The library capacity and titer of the constructed cDNA library were 3.232 × 10⁸ CFU and 1.616 × 10⁸ CFU/mL, respectively. Then, 38 candidate CtNAC78-interacting proteins were identified using a bait expression vector fused with CtNAC78 gene fragment (pGBKT7-CtNAC78A). Further yeast spotting analyses and bimolecular fluorescence complementation (BiFC) assays showed that CtE3 (ubiquitin ligase) was the CtNAC78-interacting protein. These findings can assist us in further elucidating the mechanism by which CtNAC78 regulates drought tolerance in safflower.