Metabolic gene expression and centelloside production in elicited Centella asiatica hairy root cultures

The most economically important centellosides, madecassoside and asiaticoside, are produced in very low amounts in Centella asiatica (L.) Urban roots. With the aim of overcoming this limitation, in this work we compared the effect of different elicitors on centelloside production in hairy root cultures established by Agrobacterium rhizogenes infection. Additionally, elicitor-induced changes in the expression of key biosynthetic genes were studied to shed light on the regulation of the triterpene metabolic pathway. The elicitors tested were coronatine and methyl jasmonate, added separately or together, and salicylic acid. The content of the four main centellosides (asiaticoside, madecassoside, asiatic acid and madecassic acid) was determined by HPLC/DAD, and the expression level of genes after elicitation was analyzed by real-time quantitative polymerase chain reaction. The greatest increase in the production of centellosides, especially madecassoside, was achieved with coronatine, applied alone or with methyl jasmonate. This treatment also enhanced the expression of the target genes, particularly at the start of elicitation. By far the most highly expressed were those involved in oxidations, indicating that the tested elicitors did not act specifically on key genes in the centelloside biosynthetic pathway. These results support that hairy roots are a promising biotechnological platform for improved centelloside production and that this approach warrants further research.