Dopamine Enhances the Resistance of Apple to Infection.

Apple canker is considered one of the most serious apple diseases. Dopamine is a catecholamine with key physiological functions in plants. Tyrosine decarboxylase (TYDC) is not only involved in the synthesis of dopamine in plants but may also play an important role in the resistance of plants to pathogen infection. In this study, we show that 100-μM exogenous dopamine application and () overexpression (or overexpressing, OE) enhances the resistance of apple to infection, likely because the increased dopamine content reduces the accumulation of HO and increases the accumulation of phenolic compounds and salicylic acid (SA) in dopamine-treated and OE apple plants. The activity of chitinase and β-1, 3-glucanase and the expression of SA-related genes were induced more strongly by in dopamine-treated and OE apples. The dopamine content was significantly higher in dopamine-treated and OE apples than in their respective controls under both normal and inoculated conditions ( < 0.05). Overall, these findings indicate that the application of exogenous dopamine and the OE of may enhance the resistance of apples to infection by altering the dopamine content, which improves antioxidant capacity, promotes the accumulation of phenolic compounds and SA, and enhances the activity of disease resistance-related proteins.