Fast Pyrolysis of Hemicelluloses into Short-Chain Acids: An Investigation on Concerted Mechanisms

The nature of the main primary mechanisms involved in lignocellulosic fast pyrolysis is often assumed to be radical mechanisms. Here we demonstrate that thermal depolymerization of native hemicelluloses can undergo several primary and secondary concerted reactions leading to light oxygenates that can compete with radical mechanisms. To model these reactions at a microscopic level, we used high-level quantum calculations based on functional theory. In parallel, a set of experimental data was collected to confirm the main structural features of extracted and purified hemicelluloses and to describe chemical variations within fast pyrolysis products released from various hemicellulosic fractions at 823 K. In general, the barriers computed at 800 K for pericyclic reactions were found to be reasonably low competing with these of homolytic reactions. The critical role of hydrogen bonding and spatial arrangement on product distribution was clearly demonstrated, stabilizing effects depending greatly on temperature. We reported a useful data set of intrinsic kinetic parameters and a reaction network readily available to complete kinetic models for “primary” and “secondary” fast pyrolysis of hemicelluloses

Interactions between callose and cellulose revealed through the analysis of biopolymer mixtures.

The properties of (1,3)-β-glucans (i.e., callose) remain largely unknown despite their importance in plant development and defence. Here we use mixtures of (1,3)-β-glucan and cellulose, in ionic liquid solution and hydrogels, as proxies to understand the physico-mechanical properties of callose. We show that after callose addition the stiffness of cellulose hydrogels is reduced at a greater extent than predicted from the ideal mixing rule (i.e., the weighted average of the individual components' properties). In contrast, yield behaviour after the elastic limit is more ductile in cellulose-callose hydrogels compared with sudden failure in 100% cellulose hydrogels. The viscoelastic behaviour and the diffusion of the ions in mixed ionic liquid solutions strongly indicate interactions between the polymers. Fourier-transform infrared analysis suggests that these interactions impact cellulose organisation in hydrogels and cell walls. We conclude that polymer interactions alter the properties of callose-cellulose mixtures beyond what it is expected by ideal mixing

Stomatal Opening Involves Polar, Not Radial, Stiffening Of Guard Cells

It has long been accepted that differential radial thickening of guard cells plays an important role in the turgor-driven shape changes required for stomatal pore opening to occur [1-4]. This textbook description derives from an original interpretation of structure rather than measurement of mechanical properties. Here we show, using atomic force microscopy, that although mature guard cells display a radial gradient of stiffness, this is not present in immature guard cells, yet young stomata show a normal opening response. Finite element modeling supports the experimental observation that radial stiffening plays a very limited role in stomatal opening. In addition, our analysis reveals an unexpected stiffening of the polar regions of the stomata complexes, both in Arabidopsis and other plants, suggesting a widespread occurrence. Combined experimental data (analysis of guard cell wall epitopes and treatment of tissue with cell wall digesting enzymes, coupled with bioassay of guard cell function) plus modeling lead us to propose that polar stiffening reflects a mechanical, pectin-based pinning down of the guard cell ends, which restricts increase of stomatal complex length during opening. This is predicted to lead to an improved response sensitivity of stomatal aperture movement with respect to change of turgor pressure. Our results provide new insight into the mechanics of stomatal function, both negating an established view of the importance of radial thickening and providing evidence for a significant role for polar stiffening. Improved stomatal performance via altered cell-wall-mediated mechanics is likely to be of evolutionary and agronomic significance

Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils, our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in unesterified pectins. We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the pme6-1 mutant is rescued by maintaining the plants in elevated CO2, substantiating gas exchange analyses, indicating that the mutant stomata can bestow an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology

Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin-cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering.Bourdon et al. demonstrate the possibility to ectopically synthesize callose, a polymer restricted to primary cell walls, into Arabidopsis and aspen secondary cell walls to manipulate their ultrastructure and ultimately reduce their recalcitrance

Raw data for "A comparative meta-proteomic pipeline for the identification of plasmodesmata proteins and regulatory conditions in diverse plant species"

This repository contains the raw data for the publication listed in the title. Abstract: A major route for cell-to-cell signaling in plants is mediated by cell wall-embedded pores termed plasmodesmata forming the symplasm. Plasmodesmata regulate plant development and responses to the environment however, our understanding of what factors or regulatory cues affect their structure and permeability is still limited. In this paper, a meta-analysis was carried out for the identification of conditions affecting plasmodesmata transport and for the in silico prediction of plasmodesmata proteins in species for which the plasmodesmata proteome has not been experimentally determined

Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall.

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape [1]. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils [2], our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in un-esterified pectins. We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the pme6-1 mutant is rescued by maintaining the plants in elevated CO2, substantiating gas exchange analyses, indicating that the mutant stomata can bestow an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology

Research data supporting “Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils”

The repository is divided in distinct folders which contain the raw data necessary to produce each figure of the “Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils” manuscript. As such, each folder is named after the figure it is referring to, and often contains several subfolders distinguishing the different data sets necessary to produce each figure. Each subfolder name ends up with the initials of the main co-author(s) originating the data they contain. See the 'Repository_readme' file for a detailed description of this dataseto The UK High-Field Solid-State NMR Facility used in this research was funded by EPSRC and BBSRC (EP/T015063/1) as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). We thank the Cambridge Advanced Imaging Center (CAIC) for providing access to their TEM resources and for technical assistance in imaging. The lignin analysis was supported by the Soluserre funding (Région Pays de la Loire, France). The authors acknowledge the funding received from the New Zealand Ministry of Business, Innovation, and Employment (MBIE) Strategic Science Investment Fund (Contract No. C0X41703, High-Value Biorefineries Portfolio) for supporting this work. FV acknowledges support from the Swedish Research Council (grants 621-2014-5295 and 2020-04720) and from the Knut and Alice Wallenberg Foundation (through the Wallenberg Wood Science Centre). Work in the YBA lab is supported by the Leverhulme Trust (Grant RPG-2016-136) which funded S.A. and C.P. and the UKRI Future Leader Fellowship program (MR/T04263X/1). Work in the JJL lab is supported by a grant from the National Science Centre Poland awarded to JJL as part of the SONATINA 3 programme (project number 2019/32/C/NZ3/00392) and a grant from National Science Centre Poland awarded as part of SONATA 17 programme (project number 2021/43/D/NZ9/01978). MB was supported by the ERC Proof of Concept APPLICAL (2020-2022) and the HiLife Proof of Concept APPLICAL (2020-2021) grants. L.K. received funding from the SNSF (P2LAP3_178062) and a Marie Curie IEF (No. 795250). Work in the YH lab was supported by the Finnish CoE in Molecular Biology of Primary Producers (Academy of Finland CoE programme 2014–2019) decision n°. 271832, the Gatsby Foundation (GAT3395/PR3), the University of Helsinki (award 799992091) and the ERC Advanced Investigator Grant SYMDEV (No. 323052)

Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils.

Acknowledgements: We thank G. Evans for technical support with microscopy experiments; L. Wang for statistical analysis assistance; G. Hindle, J. Salmon and S. Ward for media preparation; K. Blajecka for technical assistance; J. Daff, L. Tully, B. Fidget, A. Jootoo and G. Porteous for Horticulture assistance; M. Calatraba for lignin analysis; T. Weber from the ETH X-Ray Service Platform for technical support with the SAXS equipment; and K. Kainulainen for in vitro maintenance and horticulture assistance. R.C. was supported by UK BBSRC (Grant BB/R015783/1) to R.D. The UK High-Field Solid-State NMR Facility used in this research was funded by EPSRC and BBSRC (EP/T015063/1) as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). We thank the Cambridge Advanced Imaging Centre (CAIC) for providing access to their TEM resources and for technical assistance in imaging. Lignin analysis was supported by the Soluserre funding (Région Pays de la Loire, France). The authors acknowledge the funding received from the New Zealand Ministry of Business, Innovation, and Employment (MBIE) Strategic Science Investment Fund (Contract No. C0X41703, High-Value Biorefineries Portfolio). Part of this research was conducted as part of the Scion-INRAE-U Montpellier–Institut Agro Associated International Laboratory BIOMATA. F.V. acknowledges support from the Swedish Research Council (grants 621-2014-5295 and 2020-04720) and from the Knut and Alice Wallenberg Foundation (through the Wallenberg Wood Science Centre). Work in the Y.B.-A. lab was supported by the Leverhulme Trust (Grant RPG-2016-136), which funded S.A., and the UKRI Future Leader Fellowship programme (MR/T04263X/1). Work in the J.J.L. lab was supported by a grant from the National Science Centre Poland awarded to J.J.L. as part of the SONATINA 3 programme (project number 2019/32/C/NZ3/00392) and a grant from the National Science Centre Poland awarded as part of the SONATA 17 programme (project number 2021/43/D/NZ9/01978). M.B. was supported by ERC Proof of Concept APPLICAL (2020-2022) and HiLife Proof of Concept APPLICAL (2020-2021) grants. L.K. received funding from the SNSF (P2LAP3_178062) and a Marie Curie IEF (No. 795250). Work in the Y.H. lab was supported by the Finnish CoE in Molecular Biology of Primary Producers (Academy of Finland CoE programme 2014–2019; decision no. 271832), the Gatsby Foundation (GAT3395/PR3), the University of Helsinki (award 799992091) and the ERC Advanced Investigator Grant SYMDEV (No. 323052).Funder: Matthieu Bourdon was supported by the ERC Proof of Concept APPLICAL (2020-2022) and the HiLife Proof of Concept APPLICAL (2020-2021) grantsFunder: Work in the Lyczakowski lab is supported by a grant from the National Science Centre Poland awarded to JJL as part of the SONATINA 3 programme (project number 2019/32/C/NZ3/00392) and a grant from National Science Centre Poland awarded as part of SONATA 17 programme (project number 2021/43/D/NZ9/01978)Funder: The UK High-Field Solid-State NMR Facility used in this research was funded by EPSRC and BBSRC (EP/T015063/1) as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF)Funder: Francisco Vilaplana acknowledges support from the Swedish Research Council (grants 621-2014-5295 and 2020-04720) and from the Knut and Alice Wallenberg Foundation (through the Wallenberg Wood Science Centre)Funder: funding received from the New Zealand Ministry of Business, Innovation, and Employment (MBIE) Strategic Science Investment Fund (Contract No. C0X41703, High-Value Biorefineries Portfolio)Funder: Lothar Kalmbach received funding from the SNSF (P2LAP3_178062) and a Marie Curie IEF (No. 795250)Funder: The lignin analysis was supported by the Soluserre funding (Région Pays de la Loire, France)Funder: Work in the Benitez-Alfonso lab is supported by the Leverhulme Trust (Grant RPG-2016-136) which funded S.A. and C.P. and the UKRI Future Leader Fellowship program (MR/T04263X/1)Funder: Work in the Helariutta lab was supported by the Finnish CoE in Molecular Biology of Primary Producers (Academy of Finland CoE programme 2014amp;#x2013;2019) decision n°. 271832, the Gatsby Foundation (GAT3395/PR3), the University of Helsinki (award 799992091) and the ERC Advanced Investigator Grant SYMDEV (No. 323052)Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin-cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering