Systematic silencing of benzylisoquinoline alkaloid biosynthetic genes reveals the major route to papaverine in opium poppy. Desgagné-Penix, I. & Facchini, P. J Plant J, 72(2):331–344, 2012.
doi  abstract   bibtex   
Papaverine, a major benzylisoquinoline alkaloid in opium poppy (Papaver somniferum), is used as a vasodilator and antispasmodic. Conversion of the initial intermediate (S)-norcoclaurine to papaverine involves 3'-hydroxylation, four O-methylations and dehydrogenation. However, the biosynthesis of papaverine remains controversial more than a century after an initial scheme was proposed. In vitro assays and in vivo labeling studies have been insufficient to establish the sequence of conversions, the potential role for the intermediate (S)-reticuline, and the enzymes involved. We have used virus-induced gene silencing in opium poppy to individually suppress the expression of six genes with putative roles in papaverine biosynthesis. Suppression of the gene encoding coclaurine N-methyltransferase dramatically increased papaverine levels at the expense of N-methylated alkaloids indicating that the main biosynthetic route to papaverine does proceeds via N-desmethyl compounds rather than through (S)-reticuline. Suppression of genes encoding (S)-3'-hydroxy-N-methylcoclaurine 4-O-methyltransferase and norreticuline 7-O-methyltransferase, which accept certain N-desmethyl alkaloids, reduced papaverine content. In contrast, suppression of genes encoding N-methylcoclaurine 3'-hydroxylase or reticuline 7-O-methyltransferase, which are specific for N-methylated alkaloids, did not affect papaverine levels. Suppression of norcoclaurine 6-O-methyltransferase transcript levels significantly suppressed total alkaloid accumulation and implicates (S)-coclaurine as a key branch-point intermediate. The differential detection of N-desmethyl compounds in response to the suppression of specific genes highlights the primary route to papaverine. o̧pyright 2012 The Authors. The Plant Journal o̧pyright 2012 Blackwell Publishing Ltd.
@Article{desgagne-penix12systematic,
  author    = {Isabel Desgagn\'e-Penix and Peter J Facchini},
  title     = {Systematic silencing of benzylisoquinoline alkaloid biosynthetic genes reveals the major route to papaverine in opium poppy.},
  journal   = {Plant J},
  year      = {2012},
  volume    = {72},
  number    = {2},
  pages     = {331--344},
  abstract  = {Papaverine, a major benzylisoquinoline alkaloid in opium poppy (Papaver somniferum), is used as a vasodilator and antispasmodic. Conversion of the initial intermediate (S)-norcoclaurine to papaverine involves 3'-hydroxylation, four O-methylations and dehydrogenation. However, the biosynthesis of papaverine remains controversial more than a century after an initial scheme was proposed. In vitro assays and in vivo labeling studies have been insufficient to establish the sequence of conversions, the potential role for the intermediate (S)-reticuline, and the enzymes involved. We have used virus-induced gene silencing in opium poppy to individually suppress the expression of six genes with putative roles in papaverine biosynthesis. Suppression of the gene encoding coclaurine N-methyltransferase dramatically increased papaverine levels at the expense of N-methylated alkaloids indicating that the main biosynthetic route to papaverine does proceeds via N-desmethyl compounds rather than through (S)-reticuline. Suppression of genes encoding (S)-3'-hydroxy-N-methylcoclaurine 4-O-methyltransferase and norreticuline 7-O-methyltransferase, which accept certain N-desmethyl alkaloids, reduced papaverine content. In contrast, suppression of genes encoding N-methylcoclaurine 3'-hydroxylase or reticuline 7-O-methyltransferase, which are specific for N-methylated alkaloids, did not affect papaverine levels. Suppression of norcoclaurine 6-O-methyltransferase transcript levels significantly suppressed total alkaloid accumulation and implicates (S)-coclaurine as a key branch-point intermediate. The differential detection of N-desmethyl compounds in response to the suppression of specific genes highlights the primary route to papaverine. {\copyright} 2012 The Authors. The Plant Journal {\copyright} 2012 Blackwell Publishing Ltd.},
  doi       = {10.1111/j.1365-313X.2012.05084.x},
  file      = {DesgagnePenixFacchini_SystematicSilencingBenzylisoquinoline_PlantJ_2012.pdf:2012/DesgagnePenixFacchini_SystematicSilencingBenzylisoquinoline_PlantJ_2012.pdf:PDF},
  keywords  = {metabolite ms; networks},
  owner     = {fhufsky},
  pmid      = {22725256},
  timestamp = {2012.07.26},
}

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