Plants

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GLBRC's Plants Research Area

Plants

At the GLBRC, Plants researchers are developing the next generation of biomass-trait-improved crops. Because crops will continue to be grown for food and feed in the future, research focused on enhancing plants with desirable energy traits must be pursued without sacrificing grain yield and quality.

Learn about the Center's research approach

Plants Leadership

Plants Lead

Ralph’s program is aimed at decreasing plant cell wall recalcitrance to processing and improving plant value to the biorefinery, largely by: detailing lignin structure, chemistry, and reactions; delineating the effects of perturbing lignin biosynthetic pathways; ‘redesigning’ lignins in planta to...

Plants Lead

Brandizzi is a professor in the Michigan State University-U.S. Department of Energy (MSU-DOE) Plant Research Laboratory, and brings over 15 years of academic research experience to her role at GLBRC. Prior to coming to Michigan, Brandizzi was an associate professor...

Project Overview

Primary root of live Arabidopsis thaliana seedlings grown with green fluorescence-tagged monolignol probeGLBRC Plants research is highly genomics-focused. Although most plants used in agriculture have been selected for improved production of food or fiber, future bioenergy crops will have different characteristics, including high-energy yield per hectare, ease of conversion to fuels, and agricultural sustainability. Thus, while the Center's long-term efforts focus primarily on dedicated bioenergy crops such as perennial grasses and short-rotation woody species, improving basic traits in all biomass-relevant crops including the grain annuals is a priority.

Plants research projects fall under three general categories:

  • Reducing lignocellulosic biomass recalcitrance through plant cell wall modification
  • Improving the value of the biomass grown for bioenergy production
  • Integrating these and other beneficial traits into bioenergy crops that exhibit improved nutrient use and stress tolerance for sustainable, perennialized production

Plants Publications

Co-evolution of domain interactions in the chloroplast TGD1, 2, 3 lipid transfer complex specific to Brassicaceae and Poaceae plants

Yang Yang; Agnieszka Zienkiewicz; Anastasiya Lavell; Christoph Benning

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2017

The import of lipids into the chloroplast is essential for photosynthetic membrane biogenesis. This process requires an ABC transporter in the inner envelope membrane with three subunits, TRIGALACTOSYLDIACYLGLYCEROL (TGD) 1, 2, and 3 named after the oligogalactolipids that accumulate in the respective Arabidopsis thaliana mutants. Unlike Arabidopsis, in the model grass Brachypodium distachyon, chloroplast lipid biosynthesis is largely dependent on imported precursors, resulting in a characteristic difference in chloroplast lipid acyl composition between plants. Accordingly, Arabidopsis is designated as a 16:3 (acyl carbons: double bounds) plant and Brachypodium as an 18:3 plant. Repression of TGD1 (BdTGD1) in Brachypodium affected growth without triggering oligogalactolipid biosynthesis. Moreover, expressing BdTGD1 in the Arabidopsis tgd1-1 mutant restored some phenotypes but did not reverse oligogalactolipid biosynthesis. A 27-amino acid loop (L45) is solely responsible for the incomplete functioning of BdTGD1 in Arabidopsis tgd1-1. Co-evolutionary analysis and co-immunoprecipitation assays showed that the TGD1 L45 loop interacts with the Mycobacterial Cell Entry domain of TGD2. To explain the observed differences in oligogalactolipid biosynthesis between the two species, we suggest that excess monogalactosyldiacylglycerol derived from chloroplast-derived precursors in Arabidopsis tgd1-1 is converted into oligogalactolipids, a process absent from Brachypodium with reduced TGD1 levels, which assembles monogalactosyldiacylglycerol exclusively from imported precursors.

Deciphering the role of the phenylpropanoid metabolism in the tolerance of Capsicum annuum L. to Verticillium dahliae Kleb.

Marta Novo; Cristina Silvar; Fuencisla Merino; Teresa Martínez-Cortés; Fachuang Lu; John Ralph; Federico Pomar

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2017

Verticillium dahliae is an economically relevant soilborne pathogen that causes vascular wilt in several crops, including pepper (Capsicum annuum). Fungal infection is usually visualized as a vascular browning, likely due to the onset of phenylpropanoid metabolism, which also seems to play a crucial role in the tolerance of some pepper varieties. In the current work, the potential function of distinct phenylpropanoid derivatives (suberin, lignin and phenolic compounds) in the pepper tolerance response against V. dahliae, was investigated. Histochemical and biochemical analyses ruled out suberin as a key player in the pepper-fungus interaction. However, changes observed in lignin composition and higher deposition of bound phenolics in infected stems seemed to contribute to the reinforcement of cell walls and the impairment of V. dahliae colonization. Most importantly, this is the first time that the accumulation of the hydroxycinnamic acid amide N-feruloyltyramine was reported in pepper stems in response to a vascular fungus. Fungitoxic activity for that hydroxycinnamate-tyramine conjugate was demonstrated as well.

Defining the diverse cell populations contributing to lignification in Arabidopsis stems

Rebecca A. Smith; Mathias Schuetz; Steven D. Karlen; David Bird; Naohito Tokunaga; Yasushi Sato; Shawn D. Mansfield; John Ralph; Lacey Samuels

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2017

Degradation of lignin β-aryl ether units in Arabidopsis thaliana expressing LigD, LigF and LigG from Sphingomonas paucimobilis SYK-6

Ewelina Mnich; Ruben Vanholme; Paula Oyarce; Sarah Liu; Fachuang Lu; Geert Goeminne; Bodil Jørgensen; Mohammed S. Motawie; Wout Boerjan; John Ralph; Peter Ulvskov; Birger L. Møller; Nanna Bjarnholt; Jesper Harholt

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2017

Lignin is a major polymer in the secondary plant cell wall and composed of hydrophobic interlinked hydroxyphenylpropanoid units. The presence of lignin hampers conversion of plant biomass into biofuels; plants with modified lignin are therefore being investigated for increased digestibility. The bacterium Sphingomonas paucimobilis produces lignin-degrading enzymes including LigD, LigF and LigG involved in cleaving the most abundant lignin interunit linkage, the beta-aryl ether bond. In this study, we expressed the LigD, LigF and LigG (LigDFG) genes in Arabidopsis thaliana to introduce postlignification modifications into the lignin structure. The three enzymes were targeted to the secretory pathway. Phenolic metabolite profiling and 2D HSQC NMR of the transgenic lines showed an increase in oxidized guaiacyl and syringyl units without concomitant increase in oxidized beta-aryl ether units, showing lignin bond cleavage. Saccharification yield increased significantly in transgenic lines expressing LigDFG, showing the applicability of our approach. Additional new information on substrate specificity of the LigDFG enzymes is also provided.

Enhanced delignification of steam-pretreated poplar by a bacterial laccase

Rahul Singh; Jinguang Hu; Matthew R. Regner; James W. Round; John Ralph; John N. Saddler; Lindsay D. Eltis

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2017

The recalcitrance of woody biomass, particularly its lignin component, hinders its sustainable transformation to fuels and biomaterials. Although the recent discovery of several bacterial ligninases promises the development of novel biocatalysts, these enzymes have largely been characterized using model substrates: direct evidence for their action on biomass is lacking. Herein, we report the delignification of woody biomass by a small laccase (sLac) from Amycolatopsis sp. 75iv3. Incubation of steam-pretreated poplar (SPP) with sLac enhanced the release of acid-precipitable polymeric lignin (APPL) by ~6-fold, and reduced the amount of acid-soluble lignin by ~15%. NMR spectrometry revealed that the APPL was significantly syringyl-enriched relative to the original material (~16:1 vs. ~3:1), and that sLac preferentially oxidized syringyl units and altered interunit linkage distributions. sLac's substrate preference among monoaryls was also consistent with this observation. In addition, sLac treatment reduced the molar mass of the APPL by over 50%, as determined by gel-permeation chromatography coupled with multi-angle light scattering. Finally, sLac acted synergistically with a commercial cellulase cocktail to increase glucose production from SPP ~8%. Overall, this study establishes the lignolytic activity of sLac on woody biomass and highlights the biocatalytic potential of bacterial enzymes.

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