title: TTG2 controls the developmental regulation of seed coat tannins in Arabidopsis by regulating vacuolar transport steps in the proanthocyanidin pathway.
abstract: The brown color of Arabidopsis seeds is caused by the deposition of proanthocyanidins (PAs or condensed tannins) in their inner testa layer. A transcription factor complex consisting of TT2, TT8 and TTG1 controls expression of PA biosynthetic genes, just as similar TTG1-dependent complexes have been shown to control flavonoid pigment pathway gene expression in general. However, PA synthesis is controlled by at least one other gene. TTG2 mutants lack the pigmentation found in wild-type seeds, but produce other flavonoid compounds, such as anthocyanins in the shoot, suggesting that TTG2 regulates genes in the PA biosynthetic branch of the flavonoid pathway. We analyzed the expression of PA biosynthetic genes within the developing seeds of ttg2-1 and wild-type plants for potential TTG2 regulatory targets. We found that expression of TT12, encoding a MATE type transporter, is dependent on TTG2 and that TTG2 can bind to the upstream regulatory region of TT12 suggesting that TTG2 directly regulates TT12. Ectopic expression of TT12 in ttg2-1 plants partially restores seed coat pigmentation. Moreover, we show that TTG2 regulation of TT12 is dependent on TTG1 and that TTG1 and TTG2 physically interact. The observation that TTG1 interacts with TTG2, a WRKY type transcription factor, proposes the existence of a novel TTG1-containing complex, and an addendum to the existing paradigm of flavonoid pathway regulation.
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA; The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA. Electronic address: antonio.gonzalez@austin.utexas.edu.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gonzalez
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Brown
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Hatlestad
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA.
authors.forename: Neda
authors.initials: N
authors.lastname: Akhavan
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Smith
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Austin
authors.initials: A
authors.lastname: Hembd
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Moore
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: David
authors.initials: D
authors.lastname: Montes
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA; The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Trenell
authors.initials: T
authors.lastname: Mosley
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Resendez
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Huy
authors.initials: H
authors.lastname: Nguyen
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Lyndsey
authors.initials: L
authors.lastname: Wilson
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Campbell
authors.affiliation: The Freshman Research Initiative, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Duncan
authors.initials: D
authors.lastname: Sudarshan
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway, Austin, TX 78712, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Lloyd
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport / Q000502:physiology; D003116:Color; D005419:Flavonoids / Q000096:biosynthesis; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D044945:Proanthocyanidins / Q000096:biosynthesis*; D025941:Protein Interaction Mapping; D012639:Seeds / Q000378:metabolism*; D013634:Tannins / Q000096:biosynthesis*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005419:Flavonoids; D044945:Proanthocyanidins; C121067:TTG1 protein, Arabidopsis; C525050:TTG2 protein, Arabidopsis; D013634:Tannins; D014157:Transcription Factors; C436245:tt12 protein, Arabidopsis; C013221:proanthocyanidin
keywords: Flavonoids; Proanthocyanidins; Seed; TT12; TTG1; TTG2; Tannins; Testa