Abstract：Abstract NAC (NAM-ATAF-CUC)transcription factors play important roles in various stress response. This study currently, NAC4 gene were cloned from the Nicotiana tabacum, Its the coding region of the cDNA was 1 422 bp and encoded 473 amino acids. The phylogenetic tree analysis showed that the amino acid sequence encoded by the tobacco NAC4 gene has extremely high similarity with Capsicum baccatum and Durian zibethinus. The plant expression vector pSH737-35S-NAC4 was constructed and transformed into tobacco using Agrobacterium tumefaciens-mediated leaf disc. Six different transgenic lines, i.e. TP4, TP6, TP7, TP8, TP9 and TP10 as well as the wild-type lines, were subjected selected to simulate the drought tolerance of seed germination rate and seedling stage with different concentrations of mannitol simulated drought stress. The results showed that the seed germination rate was more than 40% higher than that of wild type when treated with 300 mmol/L mannitol for 15 d. The growth of wild type plant roots was obviously inhibited by observing the growth of seedling roots. The transgenic plants and wild plants 7 d were treated with 20% polyethylene glycol 6000. The results showed that under drought stress, the superoxide dismutase, The activities of enzymes and peroxidase were significantly higher than those of wild type, and the content of malondialdehyde was significantly lower than that of wild type plants. The results showed that the expression of NAC4, pyrroline-5-carboxylate synthetase (P5CS) and ornithine-oxo-acid transaminase (δ-OAT) were up-regulated under drought stress by qRT-PCR. Studies have shown that the expression of NAC4 gene may increase the drought resistance of plants. This study provides the basis for further study of the function of NAC4 gene and basic data for the creation of transgenic drought-tolerant plants.
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