title: Metabolic engineering of proanthocyanidins through co-expression of anthocyanidin reductase and the PAP1 MYB transcription factor.
abstract: Proanthocyanidins (PAs) and their monomeric building blocks, the (epi)-flavan-3-ols, are plant antioxidants that confer multiple human health benefits. The presence of PAs in forage crops is an important agronomic trait, preventing pasture bloat in ruminant animals. However, many consumed plant materials lack PAs, and there has been little success to date in introducing monomeric or polymeric flavan-3-ols de novo into plant tissues for disease prevention by dietary means or development of 'bloat-safe' forages. We report the introduction of PAs into plants by combined expression of a MYB family transcription factor and anthocyanidin reductase for conversion of anthocyanidin into (epi)-flavan-3-ol. Tobacco leaves expressing both transgenes accumulated epicatechin and gallocatechin monomers, and a series of dimers and oligomers consisting primarily of epicatechin units. The levels of PAs reached values that would confer bloat reduction in forage species. Expression of anthocyanidin reductase in anthocyanin-containing leaves of the forage legume Medicago truncatula resulted in production of a specific subset of PA oligomers.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
authors.forename: De-Yu
authors.initials: DY
authors.lastname: Xie
authors.forename: Shashi B
authors.initials: SB
authors.lastname: Sharma
authors.forename: Elane
authors.initials: E
authors.lastname: Wright
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins; D005419:Flavonoids / Q000378:metabolism; D035264:Flowers / Q000033:anatomy & histology / Q000378:metabolism; D029902:Medicago / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000073718:Pancreatitis-Associated Proteins; D018515:Plant Leaves / Q000033:anatomy & histology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000033:anatomy & histology / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000033:anatomy & histology / Q000378:metabolism*; D044945:Proanthocyanidins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015202:Protein Engineering; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; D005419:Flavonoids; D010088:Oxidoreductases; D000073718:Pancreatitis-Associated Proteins; D010940:Plant Proteins; D044945:Proanthocyanidins; D020598:Proto-Oncogene Proteins c-myb; D014157:Transcription Factors; C502612:AT1G56650 protein, Arabidopsis; C000612141:REG3A protein, human; C404987:flavan-3-ol