title: Poplar MYB115 and MYB134 Transcription Factors Regulate Proanthocyanidin Synthesis and Structure.
abstract: The accumulation of proanthocyanidins is regulated by a complex of transcription factors composed of R2R3 MYB, basic helix-loop-helix, and WD40 proteins that activate the promoters of biosynthetic genes. In poplar (genusPopulus), MYB134 is known to regulate proanthocyanidin biosynthesis by activating key flavonoid genes. Here, we characterize a second MYB regulator of proanthocyanidins, MYB115. Transgenic poplar overexpressing MYB115 showed a high-proanthocyanidin phenotype and reduced salicinoid accumulation, similar to the effects of MYB134 overexpression. Transcriptomic analysis of MYB115- and MYB134-overexpressing poplar plants identified a set of common up-regulated genes encoding proanthocyanidin biosynthetic enzymes and several novel uncharacterized MYB transcriptional repressors. Transient expression experiments demonstrated the capacity of both MYB134 and MYB115 to activate flavonoid promoters, but only in the presence of a basic helix-loop-helix cofactor. Yeast two-hybrid experiments confirmed the direct interaction of these transcription factors. The unexpected identification of dihydromyricetin in leaf extracts of both MYB115- and MYB134-overexpressing poplar led to the discovery of enhanced flavonoid B-ring hydroxylation and an increased proportion of prodelphinidins in proanthocyanidin of the transgenics. The dramatic hydroxylation phenotype of MYB115 overexpressors is likely due to the up-regulation of both flavonoid 3',5'-hydroxylases and cytochromeb5Overall, this work provides new insight into the complexity of the gene regulatory network for proanthocyanidin synthesis in poplar.
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Amy Midori
authors.identifier: http://orcid.org/0000-0001-9978-0876
authors.initials: AM
authors.lastname: James
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Dawei
authors.initials: D
authors.lastname: Ma
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Robin
authors.initials: R
authors.lastname: Mellway
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0002-9614-7079
authors.initials: A
authors.lastname: Gesell
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Vincent
authors.identifier: http://orcid.org/0000-0002-1253-948X
authors.initials: V
authors.lastname: Walker
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Lan
authors.initials: L
authors.lastname: Tran
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Don
authors.initials: D
authors.lastname: Stewart
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Michael
authors.initials: M
authors.lastname: Reichelt
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Jussi
authors.identifier: http://orcid.org/0000-0002-2138-0984
authors.initials: J
authors.lastname: Suvanto
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Juha-Pekka
authors.initials: JP
authors.lastname: Salminen
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Jonathan
authors.identifier: http://orcid.org/0000-0002-1812-1551
authors.initials: J
authors.lastname: Gershenzon
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.).|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.).|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.).
authors.forename: Armand
authors.initials: A
authors.lastname: Séguin
authors.affiliation: Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5 (A.M.J., D.M., R.M., A.G., K.Y., V.W., L.T., C.P.C.); cpc@uvic.ca.|Max-Planck Institute for Chemical Ecology, Department of Biochemistry, 07745 Jena, Germany (M.R., J.G.); cpc@uvic.ca.|Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, FI-20500 Turku, Finland (J.S., J.-P.S.); and cpc@uvic.ca.|Laurentian Forestry Centre, Natural Resources Canada, St. Foy, Quebec, Canada G1V 4C7 (D.S., A.S.) cpc@uvic.ca.
authors.forename: C Peter
authors.identifier: http://orcid.org/0000-0002-7627-7597
authors.initials: CP
authors.lastname: Constabel
mesh_terms: D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D032107:Populus / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D044945:Proanthocyanidins / Q000096:biosynthesis*; D011485:Protein Binding; D014157:Transcription Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D044945:Proanthocyanidins; D014157:Transcription Factors; C013221:proanthocyanidin