A Phenylpyruvic Acid Reductase Is Required for Biosynthesis of Tropane Alkaloids

Abstract

Solanaceous medicinal plants produce tropane alkaloids (TAs). We discovered a novel gene from Atropa belladonna, AbPPAR, which encodes a phenylpyruvic acid reductase required for TA biosynthesis. AbPPAR was specifically expressed in root pericycles and endodermis. AbPPAR was shown to catalyze reduction of phenylpyruvic acid to phenyllactic acid, a precursor of TAs. Suppression of AbPPAR disrupted TA biosynthesis through reduction of phenyllactic acid levels. In summary, we identified a novel enzyme involved in TA biosynthesis.

Functional genomics analysis reveals two novel genes required for littorine biosynthesis

“…UGT1 / LS silencing was performed in young A. belladonna seedlings as previously described (Bedewitz et al , ). After 28 d, underground parts were collected for the earlier‐mentioned gene expression analysis, and aboveground parts were used for hyoscyamine detection as previously described (Lan et al , ; Qiu et al , ).…”

“…UGT1 ‐RNAi, LS ‐RNAi and control root cultures were established and cultured as previously described (Yang et al , ). Genes of interest, rolB , rolC , NPTII , 35S::UGT1, and 35S::LS, were detected using PCR as previously described (Qiu et al , ). UGT1 and LS expression was analysed using qPCR as described earlier.…”

“…UGT1 and LS expression was analysed using qPCR as described earlier. For gene expression and metabolite analysis, root lines cultured in liquid Murashige and Skoog (MS) medium without antibiotics for 30 d were used (Qiu et al , ).…”

“…Quantification of phenyllactate, littorine, hyoscyamine, and scopolamine was performed as previously described (Bedewitz et al , ) with several modifications. Control, UGT1 ‐RNAi and LS ‐RNAi root cultures were lyophilized and ground, with 25 mg, then used for the extraction (Qiu et al , ).…”

“…Accordingly, there is a longstanding interest in elucidating the TA biosynthetic pathway. Most enzyme‐catalysed reactions associated with TA biosynthesis have been characterized, including those related to putrescine N ‐methyltransferase (PMT), N ‐methylputrescine oxidase (MPO), type III polyketide synthase (PYKS), tropinone synthase (CYP82M3), tropine‐forming reductase (TRI), aromatic amino acid aminotransferase (AT4), phenylpyruvic acid reductase (PPAR), littorine mutase (CYP80F1), and hyoscyamine 6β‐hydroxylase (H6H) (Li et al , ; Katoh et al , ; Bedewitz et al , ; Qiang et al , ; Geng et al , ; Qiu et al , ) (Fig. ).…”