Comparative gene expression analysis in saffron and wild Crocus species’ flowers

Abstract

The stigma of Crocus sativus L. flowers serves as the primary source of the world's most expensive spices, which are rich in apocarotenoids known as crocin, picrocrocin, and saffranal, contributing to its color, bitter taste, and aroma respectively. To gain a deeper insight into gene expression profiles and the partitioning of related metabolites in triploid saffron and its diploid wild relatives, this study investigated the apocarotenoid content and the expression of six key related genes in various flower tissues of saffron and wild Crocus species, including C. speciosus, C. almehensis, and C. gilanicus. The highest crocin content (26.76 %) was identified in the stigma of C. sativus, while the highest picrocrocin content (19.63 %) was found in the tepals of C. gilanicus. A strong correlation existed between crocin accumulation and the expression of the genes LcyB2, CCD2, and ALDH3I1. The expression level of UGT74AD in C. gilanicus tepals was approximately 11 times higher than that in C. sativus stigma, while crocin was undetectable in this tissue. Our findings indicate that the UGT74AD gene may also be involved in the glycosylation of other compounds, such as picrocrocin.