Hydrogen peroxide regulates the biosynthesis of phenolic compounds and antioxidant quality enhancement in lettuce under low nitrogen condition

Reduced nitrogen availability is an efficient strategy for increasing the accumulation of phenolic compounds in vegetables, but related mechanisms remain unknown. Here, the production of hydrogen peroxide (H(2)O(2)) and its potential roles in regulating phenolic biosynthesis and enhancing the antioxidant quality of lettuce under low nitrogen (LN) conditions were investigated. The LN treatment caused a rapid production of H(2)O(2), which effectively increased lettuce quality by enhancing the levels of phenolic compounds and other nutrients such as ascorbic acid, glutathione, soluble sugar, and soluble protein. The increased phenolic content was related to the higher expression levels of phenolic biosynthesis genes, including PAL, CHS, DFR, F35H, and UFGT, and higher photosynthetic capacity after H(2)O(2) addition under LN conditions. However, these positive effects were suppressed by dimethylthiourea (DMTU), a scavenger of H(2)O(2). These results suggest that H(2)O(2) as an important signal molecular mediates the LN-caused phenolic accumulation and antioxidant quality enhancement in lettuce.