Effects of NtMYC2 Overexpression on Polyphenol Synthesis and Salt Stress Resistance in Tobacco

In this study, the NtMYC2 transcription factor was successfully cloned via homologous cloning. To analyze its biological functions in polyphenol biosynthesis and salt stress resistance, we employed Realtime PCR to analyze its regulatory effect on NtCHS1, a key rate-limiting enzyme gene in flavonoid biosynthesis. NtMYC2-overexpression lines were constructed, and the differences in polyphenolic substances and key enzyme genes between the NtMYC2-overexpression lines and the wild-type lines were analyzed. The germination rate and resistance physiological indicators of tobacco seeds under salt stress were also determined. The results showed that NtMYC2 transcription factor localizes to the nucleus and functions as a positive regulator, activating the transcriptional activity of the NtCHS1 gene promoter. Overexpression of NtMYC2 significantly upregulated the expression level of several key structural enzyme genes involved in polyphenols biosynthesis pathway, such as PAL and CHS, leading to significantly increased levels of neochlorogenic acid, chlorogenic acid, and rutin content in transgenic tobacco leaves. Furthermore, compared with the wild-type controls, under 100 mmol/L NaCl treatment, the germination rate of NtMYC2-overexpressing transgenic lines was significantly increased. Under 200 mmol/L NaCl stress, the MDA and H₂O₂ content of NtMYC2-overexpressing transgenic lines were significantly reduced, while the POD and APX activities were significantly increased. In summary, NtMYC2 positively regulates key polyphenol synthesis genes, enhancing the synthesis of polyphenolic substances, and potentially enhancing plant salt stress resistance through improved oxidative stress tolerance.