The key tyrosine decarboxylase gene and its negative transcription factor for GX-50 biosynthesis in Sichuan Pepper (Zanthoxylum armatum)

The natural chemical N-[2-(3,4-methoxyphenyl)ethyl]-3-phenylacrylamide (GX-50) found in Sichuan pepper (Zanthoxylum armatum) is well known for its important applications in anti-aging and the treatment of various diseases. However, the functional tyrosine decarboxylase (TyDC) gene, which plays a pivotal role as the initial key enzyme in the biosynthetic pathway of GX-50 by catalyzing the decarboxylation of tyrosine to tyramine, has yet to be identified. We identified 19 potential TyDC genes from the Z. armatum genome. Among them, ZaTyDC14 showed the highest expression level in the husks than others, suggesting its critical role involved in GX-50 biosynthesis in this tissue. Through transient transformation of tobacco leaves and prokaryotic expression experiments, we confirmed that ZaTyDC14 catalyzed the conversion of tyrosine to tyramine. Overexpression of ZaTyDC14 reduced malondialdehyde (MDA) content, indicate of its critical role in this chemical reaction. Furthermore, our study found that the Zinc-finger protein (ZFP) binds directly to the ZaTyDC14 promoter, inhibiting its expression. Collectively, the present studies reveal the major gene involved in the decarboxylation of tyrosine during GX-50 synthesis in Sichuan pepper, as well as the probable negative regulator influencing its expression.