Modulation of benzylisoquinoline alkaloid biosynthesis by overexpression berberine bridge enzyme in Macleaya cordata

Macleaya cordata produces a variety of benzylisoquinoline alkaloids (BIAs), such as sanguinarine, protopine, and berberine, which are potential anticancer drugs and natural growth promoters. The genes encoding the berberine bridge enzyme (BBE) were isolated from M. cordata and Papaver somniferum, and then the two genes were overexpressed in M. cordata. Through liquid chromatography with triple-quadrupole mass spectrometry analysis, it was determined that McBBE-OX caused higher levels of (S)-norcoclaurine, (S)-coclaurine, (S)-N-cis-methylcoclaurine, (S)-reticuline, (S)-tetrahydrocolumbamine, (S)-tetrahydroberberine, (S)-cheilanthifoline, and (S)-scoulerine than PsBBE-OX, empty vector or control treatments. qRT-PCR analysis demonstrated that the introduced genes in the transgenic lines were all highly expressed. However, the levels of sanguinarine (SAN) and chelerythrine (CHE) in all the transgenic lines were slightly lower than those in the wild-type lines, possibly because the overexpression of McBBE causes feedback-inhibition. This is the first report on the overexpression of potential key genes in M. cordata, and the findings are important for the design of metabolic engineering strategies that target BIAs biosynthesis.