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Title: Expression of a bacterial 3-dehydroshikimate dehydratase reduces lignin content and improves biomass saccharification efficiency

Lignin confers recalcitrance to plant biomass used as feedstocks in agro-processing industries or as source of renewable sugars for the production of bioproducts. The metabolic steps for the synthesis of lignin building blocks belong to the shikimate and phenylpropanoid pathways. Genetic engineering efforts to reduce lignin content typically employ gene knockout or gene silencing techniques to constitutively repress one of these metabolic pathways. Recently, new strategies have emerged offering better spatiotemporal control of lignin deposition, including the expression of enzymes that interfere with the normal process for cell wall lignification. In this study, we report that expression of a 3-dehydroshikimate dehydratase (QsuB from Corynebacterium glutamicum) reduces lignin deposition in Arabidopsis cell walls. QsuB was targeted to the plastids to convert 3-dehydroshikimate – an intermediate of the shikimate pathway – into protocatechuate. Compared to wild-type plants, lines expressing QsuB contain higher amounts of protocatechuate, p-coumarate, p-coumaraldehyde and p-coumaryl alcohol, and lower amounts of coniferaldehyde, coniferyl alcohol, sinapaldehyde and sinapyl alcohol. 2D-NMR spectroscopy and pyrolysis-gas chromatography/mass spectrometry (pyro-GC/MS) reveal an increase of p-hydroxyphenyl units and a reduction of guaiacyl units in the lignin of QsuB lines. Size-exclusion chromatography indicates a lower degree of lignin polymerization in the transgenic lines. Therefore, our datamore » show that the expression of QsuB primarily affects the lignin biosynthetic pathway. Finally, biomass from these lines exhibits more than a twofold improvement in saccharification efficiency. We conclude that the expression of QsuB in plants, in combination with specific promoters, is a promising gain-of-function strategy for spatiotemporal reduction of lignin in plant biomass.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [1]
  1. Joint BioEnergy Inst., Emeryville, CA (United States); Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Physical Biosciences Division.
  2. Joint BioEnergy Inst., Emeryville, CA (United States); Sandia National Laboratory, Livermore, CA (United States)
  3. Joint BioEnergy Inst., Emeryville, CA (United States); Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Physical Biosciences Division; Univ. of California, Berkeley, CA (United States). Depts. of Bioengineering and Chemical & Biomolecular Engineering.
Publication Date:
OSTI Identifier:
1234074
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Plant Biotechnology Journal
Additional Journal Information:
Journal Name: Plant Biotechnology Journal; Journal ID: ISSN 1467-7644
Publisher:
Society for Experimental Biology; Association of Applied Biology
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; cell wall; lignin; QsuB; saccharification; lignin polymerization degree; bioenergy