CroSap: Elucidating the azafrine saponin pathway in crocus

Crocus sativus L. is an autumn-flowering perennial geophyte (a monocot belonging to the Iridaceae family) that forms underground corms and is rich in apocarotenoids. The key apocarotenoids including crocin, picrocrocin, and safranal present only in the stigmas, define its unique characteristics. It has recently become apparent that crocus corms are also a source of novel oleanane-type triterpenoid saponins (azafrines). However the biosynthetic route to azafrines in crocus is unknown. By understanding these processes, the Osbourn lab seeks to unlock the azafrine biosynthesis pathways in crocus. In the CroSap project, I will conduct the identification and characterization of candidate azafrine biosynthetic pathway genes through genome and transcriptome mining, phylogenetic and gene expression analysis. Identified genes will then be functionally characterised via combinatorial recombinant expression in the transient plant expression host N. benthamiana and in yeast, and the structures of the resulting compounds determined. These compounds will be purified and screened for potential immunostimulatory activity. I will also provide important new insights into the independent/convergent evolution of pathways for structurally related saponins in distantly related plant species Q. saponaria and S. officinalis (eudicots) and C. sativus (a monocot) and identify new enzyme (sub)families for the bioproduction of these pharmacology important compounds and analogues.