Apocarotenoid profiling in saffron: Tissue-specific changes across growth phases

Apocarotenoids such as crocetin, crocins, and picrocrocin are key metabolites produced in saffron (Crocus sativus L.) stigmas, conferring its organoleptic properties and contributing to ecological interactions. While their synthesis in stigmas during anthesis is well established, their redistribution and persistence across tissues during the saffron life cycle remain poorly understood. Here, we applied LC-HRMS-based metabolomic profiling to dissect the temporal and spatial dynamics of apocarotenoids in multiple tissues (stigma, ovary, peduncle, corm, mother corm, and two types of roots) across three key developmental stages: November (flowering and stigma senescence), March (corm enlargement with green leaves), and April (leaf senescence and corm feeding on maternal reserves). Overall, our analyses revealed pronounced tissue-specific specialization. More in detail, stigmas accumulated the highest diversity and relative abundance of trans-crocins during anthesis, ovaries became the predominant sink in spring, root tissues showed marked enrichment of crocins 6-8 and crocetin-lipid conjugates in April, coinciding with leaf senescence. PCA and heatmap analyses confirmed clear separation of stigma samples in November and ovary/root samples in spring, reflecting dynamic reprogramming of apocarotenoid metabolism. Furthermore, cis-crocin 3 appeared specifically in the new corm in glycosylated form, suggesting de novo stabilization during corm development. Correlation analyses further revealed four major metabolite clusters, separating crocin derivatives from diverse picrocrocin-related metabolites, and highlighting isomer-specific relationships between HTTC isomers and their glycosylated products. Together, these results demonstrate that apocarotenoids synthesized in stigmas are not degraded after flowering but redistributed and chemically modified to support vegetative development, storage, and possibly protective functions in underground tissues.