Abstract:
The STORR gene fusion event is considered essential for the evolution of the promorphinan/
morphinan subclass of benzylisoquinoline alkaloids (BIAs) in opium poppy as the resulting bimodular
protein performs the isomerization of (S)- to (R)-reticuline essential for their biosynthesis.
Here, we show that of the 12 Papaver species analysed those containing the STORR
gene fusion also contain promorphinans/morphinans with one important exception. P. californicum
encodes a functionally conserved STORR but does not produce promorphinans/
morphinans. We also show that the gene fusion event occurred only once, between 16.8-24.1
million years ago before the separation of P. californicum from other Clade 2 Papaver species.
The most abundant BIA in P. californicum is (R)-glaucine, a member of the aporphine subclass
of BIAs, raising the possibility that STORR, once evolved, contributes to the biosynthesis of
more than just the promorphinan/morphinan subclass of BIAs in the Papaveraceae.
