title: An optimal defense strategy for phenolic glycoside production in Populus trichocarpa--isotope labeling demonstrates secondary metabolite production in growing leaves.
abstract: Large amounts of carbon are required for plant growth, but young, growing tissues often also have high concentrations of defensive secondary metabolites. Plants' capacity to allocate resources to growth and defense is addressed by the growth-differentiation balance hypothesis and the optimal defense hypothesis, which make contrasting predictions. Isotope labeling can demonstrate whether defense compounds are synthesized from stored or newly fixed carbon, allowing a detailed examination of these hypotheses. Populus trichocarpa saplings were pulse-labeled with 13CO2 at the beginning and end of a growing season, and the 13C signatures of phenolic glycosides (salicinoids), sugars, bulk tissue, and respired CO2 were traced over time. Half of the saplings were also subjected to mechanical damage. Populus trichocarpa followed an optimal defense strategy, investing 13C in salicinoids in expanding leaves directly after labeling. Salicinoids turned over quickly, and their production continued throughout the season. Salicin was induced by early-season damage, further demonstrating optimal defense. Salicinoids appear to be of great value to P. trichocarpa, as they command new C both early and late in the growing season, but their fitness benefits require further study. Export of salicinoids between tissues and biochemical pathways enabling induction also needs research. Nonetheless, the investigation of defense production afforded by isotope labeling lends new insights into plants' ability to grow and defend simultaneously.
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.|Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, Bloco 11T (Sala 1124), São Paulo, SP, 05508-000, Brazil.
authors.forename: Tara Joy
authors.initials: TJ
authors.lastname: Massad
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Trumbore
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Gantsetseg
authors.initials: G
authors.lastname: Ganbat
authors.affiliation: Max Planck Insitute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Reichelt
authors.affiliation: Max Planck Insitute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany.
authors.forename: Sybille
authors.initials: S
authors.lastname: Unsicker
authors.affiliation: Max Planck Insitute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Boeckler
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Gleixner
authors.affiliation: Max Planck Insitute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
authors.affiliation: Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Ruehlow
mesh_terms: D001592:Benzyl Alcohols / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002241:Carbohydrates; D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes; D005960:Glucosides / Q000378:metabolism; D006027:Glycosides / Q000378:metabolism*; D007553:Isotope Labeling; D018515:Plant Leaves / Q000254:growth & development* / Q000378:metabolism*; D032107:Populus / Q000378:metabolism* / Q000502:physiology; D012621:Seasons; D064210:Secondary Metabolism
chemical_list: D001592:Benzyl Alcohols; D002241:Carbohydrates; D002247:Carbon Isotopes; D005960:Glucosides; D006027:Glycosides; C005696:salicin; D002244:Carbon; C113068:salicortin
keywords: carbon allocation; isotope labeling; optimal defense; phenolic glycoside; salicinoid; secondary metabolite; tradeoff
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