RNAi suppression and overexpression studies of hydroxyphenylpyruvate reductase (HPPR) and rosmarinic acid synthase (RAS) genes related to rosmarinic acid biosynthesis in hairy root cultures of Coleus blumei

Hydroxyphenylpyruvate reductase (HPPR) and rosmarinic acid synthase (RAS) have been described as enzymes involved in rosmarinic acid (RA) biosynthesis. In this study, elucidating the role of HPPR and RAS in the formation of RA was pursued. For this purpose, hairy root lines of Coleus blumei carrying HPPR or RAS RNAi suppression and overexpression constructs were established using Agrobacterium rhizogenes-mediated transformation. Transgenic lines were evaluated for RA accumulation. Hairy root lines showing undetectable HPPR or RAS mRNA levels displayed strongly reduced RA contents with reduction of up to 92 % compared to control hairy root lines. An increase of RA levels up to 176 % was shown in overexpression hairy root lines with equally increased HPPR transcript levels while RAS overexpression resulted in co-suppression effects with reduced RA levels. These observations support the participation of HPPR and RAS in RA biosynthesis.