Metabolic engineering of crocins and picrocrocin apocarotenoids in potato group phureja

Abstract

The stigmas of Crocus sativus accumulate the exclusive apocarotenoids crocin and picrocrocin, which are dried and desiccated to make commercial saffron. In addition to providing characteristic organoleptic qualities, saffron apocarotenoids are valuable compounds in the pharmaceutical and health industries. Previously, we developed Desirée potato tubers enriched with these apocarotenoids which also showed increased potential benefits for human health. In the current study, Solanum tuberosum (S. tuberosum) Group Phureja 01H15 which accumulates high levels of zeaxanthin, was engineered to produce saffron apocarotenoids to increase the levels of these metabolites in potato tubers using a construct namely O6, which contains the CsCCD2L, UGT74AD1, and UGT709G1 genes necessary for the biosynthesis of crocin and picrocrocin under the control of the patatin promoter. Here, we obtained transgenic S. tuberosum Group Phureja 01H15 lines with high concentrations of crocins and picrocrocin (up to 3.648 mg/g DW, 2.345 mg/g DW, respectively), which were up to 10 and 3 times higher than those obtained in the Desirée background, respectively. Furthermore, we performed transcriptome analyses of tubers from Desirée and 01H15 wild type and carrying O6 construct. Differentially expressed gene analysis revealed transcript changes not only on tuber carotenoid and apocarotenoid genes but also in other related pathways, suggesting a possible role in isoprenoid metabolism remodeling. Thus, this heterologous system serves as a robust platform for the production of these valuable metabolites.