Journal of Chemical Ecology

, Volume 36, Issue 3, pp 286–297

Biosynthesis of Phenolic Glycosides from Phenylpropanoid and Benzenoid Precursors in Populus

  • Benjamin A. Babst
  • Scott A. Harding
  • Chung-Jui Tsai

DOI: 10.1007/s10886-010-9757-7

Cite this article as:
Babst, B.A., Harding, S.A. & Tsai, CJ. J Chem Ecol (2010) 36: 286. doi:10.1007/s10886-010-9757-7


Salicylate-containing phenolic glycosides (PGs) are abundant and often play a dominant role in plant-herbivore interactions of Populus and Salix species (family Salicaceae), but the biosynthetic pathway to PGs remains unclear. Cinnamic acid (CA) is thought to be a precursor of the salicyl moiety of PGs. However, the origin of the 6-hydroxy-2-cyclohexen-on-oyl (HCH) moiety found in certain PGs, such as salicortin, is not known. HCH is of interest because it confers toxicity and antifeedant properties against herbivores. We incubated Populus nigra leaf tissue with stable isotope-labeled CA, benzoates, and salicylates, and measured isotopic incorporation levels into both salicin, the simplest PG, and salicortin. Labeling of salicortin from [13C6]-CA provided the first evidence that HCH, like the salicyl moiety, is a phenylpropanoid derivative. Benzoic acid and benzaldehyde also labeled both salicyl and HCH, while benzyl alcohol labeled only the salicyl moiety in salicortin. Co-administration of unlabeled benzoates with [13C6]-CA confirmed their contribution to the biosynthesis of the salicyl but not the HCH moiety of salicortin. These data suggest that benzoate interconversions may modulate partitioning of phenylpropanoids to salicyl and HCH moieties, and hence toxicity of PGs. Surprisingly, labeled salicyl alcohol and salicylaldehyde were readily converted to salicin, but did not result in labeled salicortin. Co-administration of unlabeled salicylates with labeled CA suggested that salicyl alcohol and salicylaldehyde may have inhibited salicortin biosynthesis. A revised metabolic grid model of PG biosynthesis in Populus is proposed, providing a guide for functional genomic analysis of the PG biosynthetic pathway.


Poplar Salicaceae Isotope labeling Phenolic glycosides Herbivore defense Carbon-13 LC-MS 

Supplementary material

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Benjamin A. Babst
    • 1
    • 2
  • Scott A. Harding
    • 1
    • 2
  • Chung-Jui Tsai
    • 1
    • 2
    • 3
  1. 1.School of Forest Resources and Environmental ScienceMichigan Technological UniversityHoughtonUSA
  2. 2.Warnell School of Forestry and Natural ResourcesUniversity of GeorgiaAthensUSA
  3. 3.Department of GeneticsUniversity of GeorgiaAthensUSA

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