Saffron Apocarotenoids: Insights into Evolution, Gene Regulation, and Genetic Engineering Approaches for Crop Improvement

Crocus sativus L., a member of the Iridaceae family, is recognized as one of the precious medicinal plants in the world. Its dried stigma constitutes the world's costliest spice, known as saffron. It is the only plant known so far that produces apocarotenoids such as crocin, picrocrocin, and safranal in significant amounts. These molecules impart the characteristics of color, aroma, and flavor to saffron. Additionally, there are other apocarotenoids such as ββ -ionone, which has antifungal and antibacterial properties, signifying its importance in plant immunity and human health. The biosynthesis of these apocarotenoids is governed by several gene families like phytoene synthases (PSYs), ββ -carotene hydroxylases (BCHs), lycopene ββ -cyclases (LCYBs), and carotenoid cleavage dioxygenases (CCDs). Various transcription factors (TFs), including MYBs, WRKYs, MADs, and BHLH, are known to regulate the expression of apocarotenoid biosynthetic genes. These TFs are also vital to saffron crop under stress conditions such as drought and soil-borne pathogens. Studies over the past few decades have shown considerable therapeutic potential of saffron. Most of these properties are attributed to these apocarotenoids having antioxidant, anticancer, telomerase inhibition activities, and their effects on diabetes, atherosclerosis, and neurodegenerative disorders. This chapter focuses on the biosynthesis of major saffron apocarotenoids, their evolutionary insights, and genetic approaches to enhance apocarotenoid-based plant performance in C. sativus .