The effects of protopine 6-hydroxylase (P6H) overexpression on benzylisoquinoline alkaloids in Macleaya cordata

Sanguinarine (SAN) and chelerythrine (CHE) have significant anti-inflammatory and growth-promoting activities and have been widely used in medicine and stockbreeding. However, SAN and CHE are present in only small amounts (0.5% capsule dry weight) in the Chinese herbal medicine Macleaya cordata , resulting in a consistently high price of their derivative products. Here, we generated transgenic plants overexpressing the key SAN and CHE biosynthetic pathway gene, protopine-6-hydroxylase (P6H), via genetic transformation. Quantitative detection by ultra-performance liquid chromatography tandem/triple quadrupole mass spectrometry (UPLC-QQQ-MS) showed that the contents of SAN and CHE increased in the overexpressing plants compared with the wild-type plants. Moreover, these plants had a higher relative expression of level of McP6H in the roots, stems and leaves, and the relative expression of the downstream enzyme dihydrobenzophenanthridine oxidase ( McDBOX ) also increased significantly. These results indicate that overexpression of the P6H gene is a promising approach to improve SAN and CHE production and is significant in the study of the synthesis pathways of benzylisoquinoline alkaloids (BIAs) to obtain germplasm resources with high alkaloid contents.