Journal Article

Over-expression of UDP-glucose pyrophosphorylase in hybrid poplar affects carbon allocation

Heather D. Coleman, Thomas Canam, Kyu-Young Kang, David D. Ellis and Shawn D. Mansfield

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 15-16, pages 4257-4268
Published in print December 2007 | ISSN: 0022-0957
Published online December 2007 | e-ISSN: 1460-2431 | DOI:

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The effects of the over-expression of the Acetobacter xylinum UDP-glucose pyrophosphorylase (UGPase) under the control of the tandem repeat Cauliflower Mosaic Virus promoter (2×35S) on plant metabolism and growth were investigated in hybrid poplar (Populus alba×grandidentata). Transcript levels, enzyme activity, growth parameters, leaf morphology, structural and soluble carbohydrates, and soluble metabolite levels were quantified in both transgenic and wild-type trees. Transgenic 2×35S::UGPase poplar showed impaired growth rates, displaying reduced height growth and stem diameter. Morphologically, 2×35S::UGPase trees had elongated axial shoots, and leaves that were substantially smaller in size when compared with wild-type trees at equivalent developmental stages. Biochemical analysis revealed significant increases in soluble sugar, starch, and cellulose contents, and concurrent decreases in lignin content. Lignin monomer composition was altered in favour of syringyl moieties. Detailed soluble metabolite analysis revealed that 2×35S::UGPase trees had as much as a 270-fold increase in the salicylic acid 2-O-β-D-glucoside (SAG), a compound typically associated with the stress response. These data suggest that while it is possible to alter the allocation of carbon in favour of cellulose biosynthesis, whole plant changes result in unexpected decreases in growth and an increase in defence metabolites.

Keywords: Carbon allocation; cellulose; hybrid poplar; sucrose metabolism; UDP-glucose; UDP-glucose pyrophosphorylase

Journal Article.  7266 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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