Fig. 6. Terpenes and aristolochic acid I biosynthesis in A. fimbriata.
a, Gas chromatogram of floral volatiles from anthetic flowers of A. fimbriata. The internal standard (IS) is 3-octanol. Fatty acid derivatives are coloured in green; benzenoid is coloured in blue; and terpenoids (sesquiterpenes and monoterpenoids) are coloured in orange. b, The phylogenetic inference of the TPS gene family using a maximum likelihood tree. Branches are coloured according to the species colour scheme on the bottom right. c, Expression patterns of the TPS genes in leaves and pre-anthetic and anthetic flowers. The TPS genes marked by stars were additionally annotated as occurring within terpene-related biosynthetic gene clusters. d, Two annotated terpene biosynthesis-related gene clusters in the A. fimbriata genome. An analysis integrating phylogenetic inference with expression pattern data suggests that Af06G158900 and Af01G154900 are functionally consequential sesquiterpene and monoterpene synthase genes, respectively. e, Our proposed aristolochic acid I biosynthesis pathway. The first four steps (grey arrows) are similar to the benzylisoquinoline alkaloid (BIA) biosynthesis pathway121–123; the subsequent two steps (orange solid arrows) are predicted and constructed on the basis of individual reactions in KEGG and previous studies124–126; the next step (orange dotted arrows) is predicted according to previous studies127,128; and the last five steps (blue dotted arrows) are predicted on the basis of previous tracer experiments121.