Ectopic Expression of a Loblolly Pine Class II 4-Coumarate:CoA Ligase Alters Soluble Phenylpropanoid Metabolism but not Lignin Biosynthesis in Populus

Robert Sykes, Mark Davis, Han-Yi Chen, Benjamin Babst, Batbayar Nyamdari, Hao Hu, Scott Harding, Chung-Jui Tsai

Research output: Contribution to journalArticlepeer-review

18 Scopus Citations

Abstract

4-Coumarate:CoA ligase (4CL) catalyzes the formation of hydroxycinnamoyl-CoA esters for phenylpropanoid biosynthesis. Phylogenetically distinct Class I and Class II 4CL isoforms occur in angiosperms, and support lignin and non-lignin phenylpropanoid biosynthesis, respectively. In contrast, the few experimentally characterized gymnosperm 4CLs are associated with lignin biosynthesis and belong to the conifer-specific Class III. Here we report a new Pinus taeda isoform Pinta4CL3 that is phylogenetically more closely related to Class II angiosperm 4CLs than to Class III Pinta4CL1. Like angiosperm Class II 4CLs, Pinta4CL3 transcript levels were detected in foliar and root tissues but were absent in xylem, and recombinant Pinta4CL3 exhibited a substrate preference for 4-coumaric acid. Constitutive expression of Pinta4CL3 in transgenic Populus led to significant increases of hydroxycinnamoyl-quinate esters at the expense of hydroxycinnamoyl-glucose esters in green tissues. In particular, large increases of cinnamoyl-quinate in transgenic leaves suggested in vivo utilization of cinnamic acid by Pinta4CL3. Lignin was unaffected in transgenic Populus, consistent with Pinta4CL3 involvement in biosynthesis of non-structural phenylpropanoids. We discuss the in vivo cinnamic acid utilization activity of Pinta4CL3 and its adaptive significance in conifer defense. Together with phylogenetic inference, our data support an ancient origin of Class II 4CLs that pre-dates the angiosperm-gymnosperm split.

Original languageAmerican English
Pages (from-to)1669-1678
Number of pages10
JournalPlant and Cell Physiology
Volume55
Issue number9
DOIs
StatePublished - 2014

Bibliographical note

Publisher Copyright:
© The Author 2014.

NREL Publication Number

  • NREL/JA-5100-63305

Keywords

  • Cinnamic acid
  • Defense
  • Phenylpropanoid
  • Pinus
  • Populus

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