Ectopic expression of safflower NAC transcription factor <i>CtNAC78</i> enhances drought tolerance in <i>Arabidopsis thaliana</i>

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 <i>CtNAC78</i> expression in safflower. Hence, to investigate <i>CtNAC78</i>'s function in drought tolerance, transgenic <i>Arabidopsis thaliana</i> with ectopic expression of <i>CtNAC78</i> was treated with drought in the present work. It was shown that the transgenic <i>A. thaliana</i> 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 <i>CtNAC78</i> enhanced drought tolerance of <i>A. thaliana</i>. 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 <i>CtNAC78</i> 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 <i>CtNAC78</i> regulates drought tolerance in safflower.