Ether bond cleavage of a phenylcoumaran beta-5 lignin model compound and polymeric lignin catalysed by a LigE-type etherase from Agrobacterium sp

A LigE-type beta-etherase enzyme from lignin-degrading Agrobacterium sp. has been identified, which assists degradation of polymeric lignins. Testing against lignin dimer model compounds revealed that it does not catalyse the previously reported reaction of Sphingobium SYK-6 LigE, but instead shows activity for a β-5 phenylcoumaran lignin dimer. The reaction products did not contain glutathione, indicating a catalytic role for reduced glutathione in this enzyme. Three reaction products were identified: the major product was a cis-stilbene arising from C−C fragmentation involving loss of formaldehyde; two minor products were an alkene arising from elimination of glutathione, and an oxidised ketone, proposed to arise from reaction of an intermediate with molecular oxygen. Testing of the recombinant enzyme against a soda lignin revealed the formation of new signals by two-dimensional NMR analysis, whose chemical shifts are consistent with the formation of a stilbene unit in polymeric lignin

Control of Flowering and Cell Fate by LIF2, an RNA Binding Partner of the Polycomb Complex Component LHP1

Polycomb Repressive Complexes (PRC) modulate the epigenetic status of key cell fate and developmental regulators in eukaryotes. The chromo domain protein LIKE HETEROCHROMATIN PROTEIN1 (LHP1) is a subunit of a plant PRC1-like complex in Arabidopsis thaliana and recognizes histone H3 lysine 27 trimethylation, a silencing epigenetic mark deposited by the PRC2 complex. We have identified and studied an LHP1-Interacting Factor2 (LIF2). LIF2 protein has RNA recognition motifs and belongs to the large hnRNP protein family, which is involved in RNA processing. LIF2 interacts in vivo, in the cell nucleus, with the LHP1 chromo shadow domain. Expression of LIF2 was detected predominantly in vascular and meristematic tissues. Loss-of-function of LIF2 modifies flowering time, floral developmental homeostasis and gynoecium growth determination. lif2 ovaries have indeterminate growth and produce ectopic inflorescences with severely affected flowers showing proliferation of ectopic stigmatic papillae and ovules in short-day conditions. To look at how LIF2 acts relative to LHP1, we conducted transcriptome analyses in lif2 and lhp1 and identified a common set of deregulated genes, which showed significant enrichment in stress-response genes. By comparing expression of LHP1 targets in lif2, lhp1 and lif2 lhp1 mutants we showed that LIF2 can either antagonize or act with LHP1. Interestingly, repression of the FLC floral transcriptional regulator in lif2 mutant is accompanied by an increase in H3K27 trimethylation at the locus, without any change in LHP1 binding, suggesting that LHP1 is targeted independently from LIF2 and that LHP1 binding does not strictly correlate with gene expression. LIF2, involved in cell identity and cell fate decision, may modulate the activity of LHP1 at specific loci, during specific developmental windows or in response to environmental cues that control cell fate determination. These results highlight a novel link between plant RNA processing and Polycomb regulation

Assessment strategy for bacterial lignin depolymerization : Kraft lignin and synthetic lignin bioconversion with Pseudomonas putida

In order to better understand bacterial depolymerization of lignin, a new analytical approach was proposed using Pseudomonas putida KT2440 as delignifying bacterium and Escherichia coli as non-delignifying control. Two different types of lignins, technical Kraft lignin and synthetic dehydrogenopolymer (DHP), were submitted to a bioconversion kinetic study over 7 days. The concomitant analysis of the supernatant acid-precipitable lignin fraction and water-soluble extractives by high-performance size-exclusion chromatography (HPSEC) and gas chromatography – mass spectrometry (GC–MS) highlighted the specific action of P. putida towards these substrates, with the transitory formation of phenolic metabolites (dihydroferulic acid for Kraft lignins and dimers for DHP) and the prevention of Kraft lignin self-assemblying. In both cases lignin apparent depolymerization followed by repolymerization was observed. The analysis of the bacterial pellets indicated the time-increasing content of lignins associated to bacterial cells, which could account for the apparent structural changes observed with E. coli in the supernatant

Maize cytokinin oxidase genes: differential expression and cloning of two new cDNAs

5 ref. DOI:10.1093/jxb/erh274International audienc

Tuning the functional properties of lignocellulosic films by controlling the molecular and supramolecular structure of lignin

| openaire: EC/H2020/720303/EU//Zelcor Funding Information: This work was funded by the Bio Based Industry Joint Undertaking under the European Union's Horizon 2020 research and innovation programme within the Zelcor project (under the grant number No 720303 ), part of the COFILI project (grant number D201550245 ) for AFM measurements funded by the Grand Est Region and the European FEDER Programme and the Lignoxyl project for EPR measurements supported by the Agence Nationale de la Recherche (ANR) through the Carnot Institutes 3BCAR ( www.3bcar.fr ) and Qualiment ( https://qualiment.fr/ ) (no. 3 no. 19-CARN-001-01 and no. 16-CARN 001-01). The EPR data in this manuscript were obtained using equipment supported jointly by the French National Ministry of Research (PPF IRPE), the “Fondation pour la Recherche Médicale” (FRM DGE20061007745), and the CNRS (Department of Chemistry and Life Sciences). The IJPB benefits from the support of the LabEx Saclay Plant Sciences-SPS (ANR-10-LABX-552 0040-SPS). Funding Information: This work was funded by the Bio Based Industry Joint Undertaking under the European Union's Horizon 2020 research and innovation programme within the Zelcor project (under the grant number No 720303), part of the COFILI project (grant number D201550245) for AFM measurements funded by the Grand Est Region and the European FEDER Programme and the Lignoxyl project for EPR measurements supported by the Agence Nationale de la Recherche (ANR) through the Carnot Institutes 3BCAR (www.3bcar.fr) and Qualiment (https://qualiment.fr/) (no. 3 no. 19-CARN-001-01 and no. 16-CARN 001-01). The EPR data in this manuscript were obtained using equipment supported jointly by the French National Ministry of Research (PPF IRPE), the ?Fondation pour la Recherche M?dicale? (FRM DGE20061007745), and the CNRS (Department of Chemistry and Life Sciences). The IJPB benefits from the support of the LabEx Saclay Plant Sciences-SPS (ANR-10-LABX-552 0040-SPS). Publisher Copyright: © 2021 The Authors Copyright: Copyright2021 Elsevier B.V., All rights reserved.This study investigated the relationships between lignin molecular and supramolecular structures and their functional properties within cellulose-based solid matrix, used as a model biodegradable polymer carrier. Two types of derivatives corresponding to distinct structuration levels were prepared from a single technical lignin sample (PB1000): phenol-enriched oligomer fractions and colloidal nanoparticles (CLP). The raw lignin and its derivatives were formulated with cellulose nanocrystals or nanofibrils to prepare films by chemical oxidation or pressure-assisted filtration. The films were tested for their water and lignin retention capacities, radical scavenging capacity (RSC) and antimicrobial properties. A structural investigation was performed by infrared, electron paramagnetic resonance spectroscopy and microscopy. The composite morphology and performance were controlled by both the composition and structuration level of lignin. Phenol-enriched oligomers were the compounds most likely to interact with cellulose, leading to the smoothest film surface. Their RSC in film was 4- to 6-fold higher than that of the other samples. The organization in CLP led to the lowest RSC but showed capacity to trap and stabilize phenoxy radicals. All films were effective against S. aureus (gram negative) whatever the lignin structure. The results show the possibility to tune the performances of these composites by exploiting lignin multi-scale structure.Peer reviewe

Enhancing the antioxidant activity of technical lignins by combining solvent fractionation and ionic-liquid treatment

International audienceA grass soda technical lignin (PB1000) underwent a process combining solvent fractionation and treatment with an ionic liquid (IL), and a comprehensive investigation of the structural modifications was performed by using high-performance size-exclusion chromatography, P-31 NMR spectroscopy, thioacidolysis, and GC-MS. Three fractions with distinct reactivity were recovered from successive ethyl acetate (EA), butanone, and methanol extractions. In parallel, a fraction deprived of EA extractives was obtained. The samples were treated with methyl imidazolium bromide ([HMIM]Br) by using either conventional heating or microwave irradiation. The treatment allowed us to solubilize 28 % of the EA-insoluble fraction and yielded additional free phenols in all the fractions, as a consequence of depolymerization and demethylation. The gain of the combined process in terms of antioxidant properties was demonstrated through 2,2-diphenyl-1-picrylhydrazyl (DPPH.) radical-scavenging tests. Integrating further IL safety-related data and environmental considerations, this study paves the way for the sustainable production of phenolic oligomers competing with commercial antioxidants