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Title: A 5-enolpyruvylshikimate 3-phosphate synthase functions as a transcriptional repressor in Populus

Long-lived perennial plants, with distinctive habits of inter-annual growth, defense, and physiology, are of great economic and ecological importance. However, some biological mechanisms resulting from genome duplication and functional divergence of genes in these systems remain poorly studied. Here, we discovered an association between a poplar (Populus trichocarpa) 5-enolpyruvylshikimate 3-phosphate synthase gene (PtrEPSP) and lignin biosynthesis. Functional characterization of PtrEPSP revealed that this isoform possesses a helix-turn-helix motif in the N-terminus and can function as a transcriptional repressor that regulates expression of genes in the phenylpropanoid pathway in addition to performing its canonical biosynthesis function in the shikimate pathway. We demonstrated that this isoform can localize in the nucleus and specifically binds to the promoter and represses the expression of a SLEEPER-like transcriptional regulator, which itself specifically binds to the promoter and represses the expression of PtrMYB021 (known as MYB46 in Arabidopsis thaliana), a master regulator of the phenylpropanoid pathway and lignin biosynthesis. Analyses of overexpression and RNAi lines targeting PtrEPSP confirmed the predicted changes in PtrMYB021 expression patterns. These results demonstrate that PtrEPSP in its regulatory form and PtrhAT form a transcriptional hierarchy regulating phenylpropanoid pathway and lignin biosynthesis in Populus.
Authors:
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  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States)
  4. Univ. of North Texas, Denton, TX (United States)
  5. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  6. West Virginia Univ., Morgantown, WV (United States)
  7. ArborGen Inc., Ridgeville, SC (United States)
  8. HudsonAlpha Inst. for Biotechnology, Huntsville, AL (United States)
Publication Date:
Report Number(s):
NREL/JA-2700-71648
Journal ID: ISSN 1040-4651
Grant/Contract Number:
AC36-08GO28308; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Plant Cell
Additional Journal Information:
Journal Volume: 30; Journal Issue: 7; Journal ID: ISSN 1040-4651
Publisher:
American Society of Plant Biologists
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; poplar; lignin biosynthesis; transcriptional repressors; populus
OSTI Identifier:
1457659
Alternate Identifier(s):
OSTI ID: 1441118