Transcriptome analysis reveals in vitro-cultured regeneration bulbs as a promising source for targeted Fritillaria cirrhosa steroidal alkaloid biosynthesis.

The bulbs of Fritillaria cirrhosa is wildly used in traditional Chinese medicine to treat lung-related disease, which has recently been found to have antitussive, anti-inflammatory, antihypertensive and anti-tumor activity. Steroidal alkaloids are the major effective ingredients of F. cirrhosa. In the current study, we demonstrated an efficient strategy for F. cirrhosa bulb regeneration in vitro by cytokinin/auxin induction. Our data showed that the regenerated bulbs accumulated higher alkaloid content that the wild ones. We further performed RNA-seq and bioinformatics analysis to study the gene expression profile, especially those related to alkaloids biosynthesis. KEGG pathway annotation identified genes related to "Metabolic pathways" were the most abundant (2644, 26.0%), followed by those for "Biosynthesis of secondary metabolites" (1319, 13.0%) among the 113,865 unigenes identified. Further analysis suggested MEP pathway, other than MVA pathway, might be the major route for steroidal alkaloid biosynthesis of F. cirrhosa, as all the key genes in this pathway were found to be unregulated in our study. We also showed that accumulation of different phytochemicals was linked to plant hormone addition. Our current study demonstrated that in vitro cultivation is a promising strategy for mass production of F. cirrhosa steroidal alkaloids for pharmacological industry.