OpenPlant researchers publish a strategy to improve conversion of plant biomass to sugars for bioenergy

A new publication from the lab of OpenPlant PI Prof. Paul Dupree, University of Cambridge in Biotechnology for Biofuels describes work to improve processing of softwood to biofuels using a synthetic biology strategy to express and assay conifer cell wall synthesis enzymes.

Lyczakowski, J.J., Wicher, K.B., Terrett, O.M., Faria-Blanc, N., Yu, X., Brown, D., Krogh, K.B.R.M., Dupree, P., and Busse-Wicher, M. (2017). Removal of glucuronic acid from xylan is a strategy to improve the conversion of plant biomass to sugars for bioenergy. Biotechnology for Biofuels 10: 224

Abstract

Background: Plant lignocellulosic biomass can be a source of fermentable sugars for the production of second generation biofuels and biochemicals. The recalcitrance of this plant material is one of the major obstacles in its conversion into sugars. Biomass is primarily composed of secondary cell walls, which is made of cellulose, hemicelluloses and lignin. Xylan, a hemicellulose, binds to the cellulose microfibril and is hypothesised to form an interface between lignin and cellulose. Both softwood and hardwood xylan carry glucuronic acid side branches. As xylan branching may be important for biomass recalcitrance and softwood is an abundant, non-food competing, source of biomass it is important to investigate how conifer xylan is synthesised.

Results: Here, we show using Arabidopsis gux mutant biomass that removal of glucuronosyl substitutions of xylan can allow 30% more glucose and over 700% more xylose to be released during saccharification. Ethanol yields obtained through enzymatic saccharification and fermentation of gux biomass were double those obtained for non-mutant material. Our analysis of additional xylan branching mutants demonstrates that absence of GlcA is unique in conferring the reduced recalcitrance phenotype. As in hardwoods, conifer xylan is branched with GlcA. We use transcriptomic analysis to identify conifer enzymes that might be responsible for addition of GlcA branches onto xylan in industrially important softwood. Using a combination of in vitro and in vivo activity assays, we demonstrate that a white spruce (Picea glauca) gene, PgGUX, encodes an active glucuronosyl transferase. Glucuronic acid introduced by PgGUX reduces the sugar release of Arabidopsis gux mutant biomass to wild-type levels indicating that it can fulfil the same biological function as native glucuronosylation.

Conclusion: Removal of glucuronic acid from xylan results in the largest increase in release of fermentable sugars from Arabidopsis plants that grow to the wild-type size. Additionally, plant material used in this work did not undergo any chemical pretreatment, and thus increased monosaccharide release from gux biomass can be achieved without the use of environmentally hazardous chemical pretreatment procedures. Therefore, the identification of a gymnosperm enzyme, likely to be responsible for softwood xylan glucuronosylation, provides a mutagenesis target for genetically improved forestry trees.

[Closes 11 Oct 2017] Knowledge Frontiers: International Interdisciplinary Research Projects

The British Academy is inviting proposals from UK-based researchers across all disciplines within the social sciences and humanities to develop international interdisciplinary research projects with development impact, in collaboration with colleagues from the natural, engineering and/or medical sciences.

Aims

The purpose of each project will be to develop new ideas and methods to bear on existing international challenges and to deliver policy-relevant outputs which could potentially improve the welfare of people in developing countries. Proposals that creatively tackle cultural, public and/or policy controversies, or explore how such controversies have been understood and responded to in the past, would be particularly welcome. Such controversies might include, but need not be limited to, changing climate, movements across borders, socio-biological problems, artificial intelligence, medical humanities, people and infrastructures, and responses to or understanding of diseases and pathogens.

The complexities of global change and the proliferation of diverse communities of knowledge, practice and intelligence highlight the necessity of collaborative engagement between communities of practice, disciplines, capacities and borders. The British Academy is keen to support and work with proposals that strengthen understanding of challenges in this context and engage with questions concerning the relationship between expertise, public understanding and policy delivery. We are interested in projects of interdisciplinary nature that examine encounters between academic, professional and lay knowledge, and how valid knowledge, knowledge associations and evidence are built and developed, communicated and disseminated, and the factors which can serve as barriers to this in different political or cultural settings.

Eligibility requirements

The lead applicant must be based at a UK university or research institute, and be of postdoctoral or above status (or have equivalent research experience). International co-applicants, and in particular co-applicants from OECD DAC countries, are strongly encouraged.

The British Academy will require applicants to demonstrate that their proposals are ODA eligible. ODA eligibility is an essential criterion – projects will only be deemed eligible for funding if they can demonstrate that they satisfy ODA eligibility criteria.

Value and Duration

Awards are of one-year in duration and are available for up to £50,000. Funding can be used to support research and/or clerical assistance; research expenses and consumables; travel and subsistence; and networking, meeting and conference costs. Awards are not funded on a full economic costs basis, with contributions to overheads an ineligible cost. 

Application Process

Application deadline: Wednesday 11 October 2017 (17.00 UK Time)

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Rapid transporter regulation prevents substrate flow traffic jams in boron transport

Researchers at the John Innes Centre collaborated with colleagues from the University of Tokyo to understand the regulation of boron transport in Arabidopsis. Nutrient uptake relies on both a regulatory circuit within cells, and a coordinated behaviour across tissues. This work used both computational and molecular biology tools to model the effects of slowing boron uptake, discovering that this peturbation of the system leads to traffic-jam like behaviour of nutrient flow. Read more about it in this JIC news article. Experiments were partly funded through the OpenPlant Fund.

Sotta, N., Duncan, S., Tanaka, M., Takafumi, S., Marée, A.F., Fujiwara, T., Grieneisen, V.A., 2017. Rapid transporter regulation prevents substrate flow traffic jams in boron transport. eLife 2017;6: e27038.

Abstract

Nutrient uptake by roots often involves substrate-dependent regulated nutrient transporters. For robust uptake, the system requires a regulatory circuit within cells and a collective, coordinated behaviour across the tissue. A paradigm for such systems is boron uptake, known for its directional transport and homeostasis, as boron is essential for plant growth but toxic at high concentrations. In Arabidopsis thaliana Boron up-take occurs via diffusion facilitators (NIPs) and exporters (BORs), each presenting distinct polarity. Intriguingly, although boron soil concentrations are homogenous and stable, both transporters manifest strikingly swift boron-dependent regulation. Through mathematical modelling, we demonstrate that slower regulation of these transporters leads to physiologically detrimental oscillatory behaviour. Cells become periodically exposed to potentially cytotoxic boron levels, and nutrient throughput to the xylem becomes hampered. We conclude that, while maintaining homeostasis, swift transporter regulation within a polarised tissue context is critical to prevent intrinsic traffic-jam like behaviour of nutrient flow.

[Closes 31 Sep 2017] PhD Studentship in sex chromosome evolution in liverworts

Evolution of sex chromosomes is well-studied in organisms in which sex is expressed in the diploid phase. In such organisms the lack of recombination and the asymmetry in haploidy are assumed to lead to the progressive decay of the Y chromosome. In organisms in which sex is expressed in the haploid phase both U and V chromosomes are equally devoid of recombination and show no asymmetry in recombination suppression. This provides a unique opportunity to tease apart the effect of this two factors on the evolutionary trajectory of sex chromosomes. We are using a combination of classical genetic and comparative genomic approaches to test hypotheses concerning sex chromosome evolution in haploid dioecy using liverworts as a suitable model system (Marchantia polymorpha, Preissia quadrata and many more).

The goal of this project is to (1) develop a new methodology for capturing and sequencing complete sex chromosomes in plant model systems and (2) to reconstruct their evolutionary history both at the gene and structural levels. Therefore, this position involves molecular laboratory work to develop and optimize capturing and sequencing protocols; bioinformatics work to analyze and interpret the generated next- generation sequencing data; and evolutionary and functional genetic analysis of the evolution of sex chromosomes in the model plant Marchantia polymorpha and other liverwort species. This project is aimed at addressing one of the fundamental questions of evolutionary biology, the genetic makeup of sex chromosomes in a haploid plant model organism, via developing a new cutting-edge method for third-generation sequencing.

The student will work 18 months at University of Zurich, Switzerland. The other 18 months at BaseClear, The Netherlands. Peter Szovenyi, University of Zurich; Prof. Elena Conti, University of Zurich, Prof. Michael Lenhard, University of Potsdam; Dr. Walter Pirovano, Dr. Adalberto Costessi and Dr. Daniël Duijsings, BaseClear BV, The Netherlands will jointly supervise the successful candidate. 

This is project is conducted in the framework of PlantHUB. PlantHUB is funded by the H2020 PROGRAMME Marie Curie Actions – People, Initial Training Networks (ITN).