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

Abstract

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:

Eudes, Aymerick ^[1]; Sathitsuksanoh, Noppadon ^[2]; Baidoo, Edward E. K. ^[1]; George, Anthe ^[2]; Liang, Yan ^[1]; Yang, Fan ^[1]; Singh, Seema ^[2]; Keasling, Jay D. ^[3]; Simmons, Blake A. ^[2]; Loqué, Dominique ^[1]

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+ Show Author Affiliations

1. Joint BioEnergy Institute, Emeryville CA USA, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley CA USA
2. Joint BioEnergy Institute, Emeryville CA USA, Sandia National Laboratory, Livermore CA USA
3. Joint BioEnergy Institute, Emeryville CA USA, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley CA USA, Department of Bioengineering, Department of Chemical & Biomolecular Engineering, University of California, Berkeley CA USA

Publication Date:

Tue Jan 13 00:00:00 EST 2015

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1234074

Alternate Identifier(s):

OSTI ID: 1213529; OSTI ID: 1234075; OSTI ID: 1619071

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Plant Biotechnology Journal

Additional Journal Information:

Journal Name: Plant Biotechnology Journal Journal Volume: 13 Journal Issue: 9; Journal ID: ISSN 1467-7644

Publisher:

Society for Experimental Biology; Association of Applied Biology

Country of Publication:

United Kingdom

Language:

English

Subject:

60 APPLIED LIFE SCIENCES; cell wall; lignin; QsuB; saccharification; lignin polymerization degree; bioenergy