Enhanced Production of Apocarotenoids by Salicylic Acid Elicitation in Cell Suspension Cultures of Saffron (Crocus sativus L.)

A cell suspension culture of saffron (Crocus sativus L.) was previously established from style-derived calli to obtain an in vitro system for crocin, an uncommon and valuable water-soluble apocarotenoid, and carotenoid production suitable for future scaling up. To shed more light on the correlation between apocarotenoid biosynthesis and key-gene expression, in this study, SA was used at 0.5 mM concentration to elicit crocin production and the effects on carotenoid production were analyzed after 6, 12, 24, and 48 h. HPLC-DAD analysis was used for total crocin quantification as well as the other carotenoids zeaxanthin, β-carotene and lutein. Quantitative RT-PCR was used to analyze the transcript levels of saffron apocarotenoid biosynthetic key genes PSY (phytoene synthase), BCH1 (β-carotene hydroxylase), and CCD2 (carotenoid cleavage dioxygenase) after SA elicitation. In saffron suspension-cultured cells elicited by SA, the carotenoid biosynthetic pathway was mostly enhanced toward crocin biosynthesis, known to exert strong biological activity and therapeutic effects, rather than lutein or xanthins. SA increased BCH1 and CCD2 gene expression 15.6 and 3.3 times, respectively, compared to the control at 24 h after elicitation. Although a dynamic change of metabolite contents and gene expression was observed during the 48 h time course in response to SA elicitation, the changes of zeaxanthin and crocin were consistent with the regulation of the corresponding genes BCH and CCD2 during the time course. In conclusion, the effects of SA on regulation of gene expression in the apocarotenoid pathway could be successfully applied for the biotechnological production of crocin.