title: Condensed tannin biosynthesis and polymerization synergistically condition carbon use, defense, sink strength and growth in Populus.
abstract: The partitioning of carbon for growth, storage and constitutive chemical defenses is widely framed in terms of a hypothetical sink-source differential that varies with nutrient supply. According to this framework, phenolics accrual is passive and occurs in source leaves when normal sink growth is not sustainable due to a nutrient limitation. In assessing this framework, we present gene and metabolite evidence that condensed tannin (CT) accrual is strongest in sink leaves and sequesters carbon in a way that impinges upon foliar sink strength and upon phenolic glycoside (PG) accrual in Populus. The work was based on two Populus fremontii × angustifolia backcross lines with contrasting rates of CT accrual and growth, and equally large foliar PG reserves. However, foliar PG accrual was developmentally delayed in the high-CT, slow-growth line (SG), and nitrogen-limitation led to increased foliar PG accrual only in the low-CT, fast-growth line (FG). Metabolite profiling of developing leaves indicated comparatively carbon-limited amino acid metabolism, depletion of several Krebs cycle intermediates and reduced organ sink strength in SG. Gene profiling indicated that CT synthesis decreased as leaves expanded and PGs increased. A most striking finding was that the nitrogenous monoamine phenylethylamine accumulated only in leaves of SG plants. The potential negative impact of CT hyper-accumulation on foliar sink strength, as well as a mechanism for phenylethylamine involvement in CT polymerization in Populus are discussed. Starch accrual in source leaves and CT accrual in sink leaves of SG may both contribute to the maintenance of a slow-growth phenotype suited to survival in nutrient-poor habitats.
authors: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA sharding@uga.edu cjtsai@uga.edu.
authors: Scott A
authors: SA
authors: Harding
authors: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA.
authors: Liang-Jiao
authors: LJ
authors: Xue
authors: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA Present address: Unit of Computational Medicine, Department of Medicine, Karolinska Institute, Stockholm 17176, Sweden.
authors: Lei
authors: L
authors: Du
authors: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA.
authors: Batbayar
authors: B
authors: Nyamdari
authors: Department of Entomology, University of Wisconsin, Madison, WI 53706, USA.
authors: Richard L
authors: RL
authors: Lindroth
authors: National Renewable Energy Laboratory, Golden, CO 80401, USA.
authors: Robert
authors: R
authors: Sykes
authors: National Renewable Energy Laboratory, Golden, CO 80401, USA.
authors: Mark F
authors: MF
authors: Davis
authors: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA Department of Genetics, University of Georgia, Athens, GA 30602, USA Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA sharding@uga.edu cjtsai@uga.edu.
authors: Chung-Jui
authors: CJ
authors: Tsai
mesh_terms: D002244:Carbon / Q000378:metabolism*; D057965:Carbon Sequestration; D002678:Chimera; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D005960:Glucosides / Q000378:metabolism; D006027:Glycosides / Q000378:metabolism; D055442:Metabolome; D009584:Nitrogen / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010627:Phenethylamines / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry / Q000254:growth & development / Q000276:immunology / Q000378:metabolism; D058105:Polymerization; D032107:Populus / Q000737:chemistry / Q000254:growth & development / Q000276:immunology / Q000378:metabolism*; D044945:Proanthocyanidins / Q000378:metabolism*; D020005:Propanols / Q000378:metabolism
chemical_list: D005960:Glucosides; D006027:Glycosides; D010627:Phenethylamines; D010636:Phenols; D044945:Proanthocyanidins; D020005:Propanols; C439395:1-phenylpropanol; D002244:Carbon; D009584:Nitrogen; C113068:salicortin
keywords: MYB; flavonoid; glycolysis; phenylethylamine; phenylpropanoid; salicortin