Lignin biosynthesis and structure

Major facilitator family transporters specifically enhance caffeyl alcohol uptake during C-lignin biosynthesis

The mode of transport of lignin monomers to the sites of polymerization in the apoplast remains controversial. C-Lignin is a recently discovered form of lignin found in some seed coats that is composed exclusively of units derived from caffeyl alcohol. RNA-seq and proteome analyses identified a number of transporters co-expressed with C-lignin deposition in the seed coat of Cleome hassleriana. Cloning and influx/efflux analysis assays in yeast identified two low-affinity transporters, ChPLT3 and ChSUC1, that were active with caffeyl alcohol but not with the classical monolignols p-coumaryl, coniferyl, and sinapyl alcohols, consistent with molecular modeling and docking studies. Expression of ChPLT3 in Arabidopsis seedlings enhanced root growth in the presence of caffeyl alcohol, and expression of ChPLT3 and ChSUC1 correlated with lignin C-unit content in hairy roots of Medicago truncatula. We present a model, consistent with phylogenetic and evolutionary considerations, whereby passive caffeyl alcohol transport may be supplemented by hitchhiking on secondary active transporters to ensure the synthesis of C-lignin, and inhibition of synthesis of G-lignin, in the apoplast.

Manipulation of the brown glume and internode 1 gene leads to alterations in the colouration of lignified tissues, lignin content and pathogen resistance in wheat

Lignin is a crucial component of the cell wall, providing mechanical support and protection against biotic and abiotic stresses. However, little is known about wheat lignin-related mutants and their roles in pathogen defence. Here, we identified an ethyl methanesulfonate (EMS)-derived Aegilops tauschii mutant named brown glume and internode 1 (bgi1), which exhibits reddish-brown pigmentation in various tissues, including internodes, spikes and glumes. Using map-based cloning and single nucleotide polymorphism (SNP) analysis, we identified AET6Gv20438400 (BGI1) as the leading candidate gene, encoding the TaCAD1 protein. The mutation occurred in the splice acceptor site of the first intron, resulting in a premature stop codon in BGI1. We validated the function of BGI1 using loss-of-function EMS and gene editing knockout mutants, both of which displayed reddish-brown pigmentation in lignified tissues. BGI1 knockout mutants exhibited reduced lignin content and shearing force relative to wild type, while BGI1 overexpression transgenic plants showed increased lignin content and enhanced disease resistance against common root rot and Fusarium crown rot. We confirmed that BGI1 exhibits CAD activity both in vitro and in vivo, playing an important role in lignin biosynthesis. BGI1 was highly expressed in the stem and spike, with its localisation observed in the cytoplasm. Transcriptome analysis revealed the regulatory networks associated with BGI1. Finally, we demonstrated that BGI1 interacts with TaPYL-1D, potentially involved in the abscisic acid signalling pathway. The identification and functional characterisation of BGI1 significantly advance our understanding of CAD proteins in lignin biosynthesis and plant defence against pathogen infection in wheat.

Lignin and Nanolignin: Next-Generation Sustainable Materials for Water Treatment

Water scarcity, contamination, and lack of sanitation are global issues that require innovations in chemistry, engineering, and materials science. To tackle the challenge of providing high-quality drinking water for a growing population, we need to develop high-performance and multifunctional materials to treat water on both small and large scales. As modern society and science prioritize more sustainable engineering practices, water treatment processes will need to use materials produced from sustainable resources via green chemical routes, combining multiple advanced properties such as high surface area and great affinity for contaminants. Lignin, one of the major components of plants and an abundant byproduct of the cellulose and bioethanol industries, offers a cost-effective and scalable platform for developing such materials, with a wide range of physicochemical properties that can be tailored to improve their performance for target water treatment applications. This review aims to bridge the current gap in the literature by exploring the use of lignin, both as solid bulk or solubilized macromolecules and nanolignin as multifunctional (nano)materials for sustainable water treatment processes. We address the application of lignin-based macro-, micro-, and nanostructured materials in adsorption, catalysis, flocculation, membrane filtration processes, and antimicrobial coatings and composites. Throughout the exploration of recent progress and trends in this field, we emphasize the importance of integrating principles of green chemistry and materials sustainability to advance sustainable water treatment technologies.

Comprehensive Structural Characterization of Wheat Bran Lignin

Wheat bran is a large volume sidestream of wheat flour production and is used in food and feed applications. Despite great advances in the characterization of the wheat bran hemicellulose component, thus far, only limited attention has been paid to wheat bran lignin. Here, we describe the comprehensive structural characterization of wheat bran lignin, facilitated by sequential enzymatic starch and protein removal, followed by mild γ-valerolactone organosolv extraction and extensive purification. Quantitative 13C-IS pyrolysis-GC-MS and HSQC NMR revealed that wheat bran lignin is enriched in syringyl subunits (S/G ∼ 0.9), as compared to wheat straw lignin (typical S/G ∼ 0.5), but surprisingly poor in p-coumarate incorporated (<1 per 100 aromatic rings), entirely free of tricin, and accordingly composed of typical β-O-4 aryl ether (84%), β-5 phenylcoumaran (7%), and β-β resinol (9%) interunit linkages. Moreover, and in line with the interunit linkage abundance (46 per 100 aromatic rings), alkaline SEC and 31P NMR, respectively, confirmed a macromolecular nature (Mw 6900 g/mol, Đ 5.9) and low phenolic hydroxyl content (1.6 mmol/g of lignin) of the wheat bran lignin structure. Our extensive characterization efforts contribute to the dedicated valorization of wheat bran lignin and support understanding potential physiological effects when incorporated into human and animal diets.

Lignin: Dissolution, modification, and derived materials

Global environmental issues and energy dilemmas have made renewable and sustainable technologies become on the cutting edge. Lignin, the most abundant non-petroleum polyhydroxy aromatic macromolecule, has been widely studied to convert to platform chemicals via violent cleavage. This makes good use of lignin, which can effectively remit environmental and energy problems. However, the self-contained three-dimensional structure was wasted in this process, and thus, the synthesis of lignin-based materials has become another important research direction. Meanwhile, the value-added utilization of technical lignin is still a problem at present. There are some limitations in taking advantage of lignin due to the different sources and isolation routes, resulting in poor solubility and compatibility in application. Technical lignins contain aliphatic hydroxyl, phenolic hydroxyl, methoxyl, and other oxygen-containing functional groups, which can be further chemically modified to adjust the technical lignins of physicochemical properties for forming available materials rather than just being used as fuel. Here, we summarized the development of technical lignins, including the following aspects: (1) the chemical structures of lignins, the critical factors that influenced the dissolution of lignin, which induced different dispersion states of lignin in the as-prepared materials; (2) the dissolution behavior and mechanism for lignins; (3) the potential chemical modification routes for lignin; and (4) preparation and properties of lignin-based hybrid and composite materials. This comprehensive review can provide valuable information on lignin dissolution, chemical modification, and further employment in the fabrication of materials.

The Distribution and Variation of Phenolic Acids in Chrysanthemum morifolium (Chuju) in Different Plant Parts During Growth Stages

Chrysanthemum is commonly known as a natural Chinese herbal medicine, whose flowers are traditionally used for edible and therapeutic purposes for health benefits. Phenolic acids are the main compounds that are considered to have important biological activity in the Chrysanthemum flower. An efficient and accurate analytical method to quantify 16 targeted phenolic acids was established and validated using a high-performance liquid chromatography method. The distribution of free and bound phenolic acids in different Chuju organs was analyzed and quantified. The detected phenolic acids were present at higher concentrations in flower materials than in other plant organs, including salicylic acid, chlorogenic acid, and vanillic acid. Second only to flowers, the leaves also could be recommended as an optimal source of certain phenolic acids, which include benzoic acid and sinapic acid. The types and contents of bound phenolic acids increased markedly in root and stem materials. Additionally, phenolic acid content fluctuated throughout the growth stages, with the highest levels observed during full flowering. Our study provided valuable information on the distribution and variation of phenolic acids in the Chuju plant at different growth stages, further providing research prospects to promote Chuju usage and function in the herbal tea and pharmaceutical industries, and even promoting Chuju cultivation.

Genome-wide identification and expression pattern analysis of the cinnamoyl-CoA reductase gene family in flax (Linum usitatissimum L.)

BACKGROUND

Cinnamoyl-CoA reductase (CCR) is the first important and committed enzyme in the monolignol synthesis branch of the lignin biosynthesis (LB) pathway, catalyzing the conversion of cinnamoyl-CoAs to cinnamaldehydes and is crucial for the growth of Linum usitatissimum (flax), an important fiber crop. However, little information is available about CCR in flax (Linum usitatissimum L.).

RESULTS

In this study, we conducted a genome-wide analysis of the CCR gene family and identified a total of 22 CCR genes. The 22 CCR genes were distributed across 9 chromosomes, designated LuCCR1-LuCCR22. Multiple sequence alignment and conserved motif analyses revealed that LuCCR7/13/15/20 harbor completely conserved NADP-specific, NAD(P)-binding, and CCR signature motifs. Furthermore, each of these LuCCRs is encoded by 5 exons separated by 4 introns, a characteristic feature of functional CCRs. Phylogenetic analysis grouped LuCCRs into two clades, with LuCCR7/13/15/20 clustering with functional CCRs involved in LB in dicotyledonous plants. RNA-seq analysis indicated that LuCCR13/20 genes are highly expressed throughout all flax developmental stages, particularly in lignified tissues such as roots and stems, with increased expression during stem maturation. These findings suggest that LuCCR13/20 play crucial roles in the biosynthesis process of flax lignin. Additionally, LuCCR2/5/10/18 were upregulated under various types of abiotic stress, highlighting their potential roles in flax defense-related processes.

CONCLUSIONS

This study systematically analyzes the CCR gene family (CCRGF) of flax (Linum usitatissimum L.) at the genomic level for the first time, so as to select the whole members of the CCRGF of flax and to ascertain their potential roles in lignin synthesis. Therefore, in future work, we can target genetic modification of LuCCR13/20 to optimize the content of flax lignin. As such, this research establishes a theoretical foundation for studying LuCCR gene functions and offers a new perspective for cultivating low-lignin flax varieties.

Sex-specific ozone stress responses of poplar: Mechanisms of enhanced tolerance of males

Uncovering whether the ozone (O3)-sensitivity differs between sexes in Populus deltoides and if so, what are the mechanisms underlying the different sensitivities is vital for understanding plant-adaptation-strategy in O3 polluted areas. We exposed female and male saplings to 80 nmol mol-1 O3 for 14 days, measured the growth, structural and physiological characteristics, metabolite accumulations, and gene transcription levels, to test the hypothesis that the enhanced resistance in males is associated with their traits detoxifying and reducing O3 entry into the cells. In general, females showed more severe visible injury, larger reductions in leaf biomass, chlorophyll content, and photosynthetic characteristics than males. The emission of isoprene and its synthase gene expression were inhibited by O3 in both sexes with less reductions in males than females. The up-regulated differentially expressed genes in males under O3 stress were mainly enriched in phenylpropanoid biosynthesis and glutathione metabolism pathways, while in females they were primarily enriched in the flavonoid biosynthesis pathway. Accordingly, males accumulated more lignin, lignans, and coumarins, while females accumulated more flavonoids. Overall, the stronger tolerance to O3 in males than females was possibly related to their combined up-regulation of multiple defense pathways that reduce both the oxidative stress and O3 permeability into cytosol.

Lignin synthesis plays an essential role in the adaptation of Haloxylon ammodendron to adverse environments

Haloxylon ammodendron is a desert shrub exhibiting remarkable tolerance to adverse environments, making it an excellent model for studying the mechanisms by which plants adapt to harsh environmental conditions. Lignin, a crucial component of plants, has been shown to play an important role in the adaptation of H. ammodendron to osmotic and salt stress. Therefore, this study was focused on the role of lignin synthesis by H. ammodendron in its adaptation to osmotic and salt stress (imposed by 0.4 % sorbitol and 350 mM NaCl, respectively). We investigated lignin deposition, the polymerization of lignin monomers, water content and adjustment of osmotic potential in assimilating branches of H. ammodendron, as well as gene expression and small molecules related to lignin biosynthesis. The results indicated that osmotic and salt stress induced the activity of peroxidase (POD) and laccase (LAC), while H2O2 concentration also increased. The genes encoding functions associated with lignin biosynthesis in both shoots and roots were upregulated and lignin accumulation in H. ammodendron increased, thereby maintaining osmotic potential and shoot water content under stress. These results showed that osmotic and salt stresses significantly increased lignin production in H. ammodendron, polymerization of lignin monomers, and the expression of genes encoding functions correlated to lignin synthesis. In addition, under osmotic stress, phenylalanine and p-coumaric acid increased in the shoots and roots, as did coniferyl alcohol and sinapyl alcohol. Overall, this study confirmed the role of lignin biosynthesis in the stress resistance of H. ammodendron, providing further insights into its adaptive strategies to adversity, and suggesting new ideas for improving the resistance of cultivated plants.

De novo biosynthesis of plant lignans by synthetic yeast consortia

Reconstructing the biosynthesis of complex natural products such as lignans in yeast is challenging and can result in metabolic promiscuity, affecting the biosynthetic efficiency. Here we divide the lignan biosynthetic pathway across a synthetic yeast consortium with obligated mutualism and use ferulic acid as a metabolic bridge. This cooperative system successfully overcomes the metabolic promiscuity and synthesizes the common precursor, coniferyl alcohol. Furthermore, combined with systematic engineering strategies, we achieve the de novo synthesis of key lignan skeletons, pinoresinol and lariciresinol, and verify the scalability of the consortium by synthesizing complex lignans, including antiviral lariciresinol diglucoside. These results provide a starting engineering platform for the heterologous synthesis of lignans. In particular, the study illustrates that the yeast consortium with obligate mutualism is a promising strategy that mimics the metabolic division of labor among multiple plant cells, thereby improving the biosynthesis of long pathways and complex natural products.

Chemistry of lignin and condensed tannins as aromatic biopolymers

Aromatic biopolymers are the second largest group of biopolymers after polysaccharides. Depolymerization of aromatic biopolymers, as cheap and renewable substitutes for fossil-based resources, has been used in the preparation of biofuels, and a range of aromatic and aliphatic small molecules. Additionally, these polymers exhibit a robust UV-shielding function due to the high content of aromatic groups. Meanwhile, the abundance of phenolic groups in their structures gives these compounds outstanding antioxidant capabilities, making them well-suited for a diverse array of anti-UV and medical applications. Nevertheless, these biopolymers possess inherent drawbacks in their pristine states, such as rigid structure, low solubility, and lack of desired functionalities, which hinder their complete exploitation across diverse sectors. Thus, the modification and functionalization of aromatic biopolymers are essential to provide them with specific functionalities and features needed for particular applications. Aromatic biopolymers include lignins, tannins, melanins, and humic acids. The objective of this review is to offer a thorough reference for assessing the chemistry and functionalization of lignins and condensed tannins. Lignins represent the largest and most prominent category of aromatic biopolymers, typically distinguishable as either softwood-derived or hardwood-derived lignins. Besides, condensed tannins are the most investigated group of the tannin family. The electron-rich aromatic rings, aliphatic hydroxyl groups, and phenolic groups are the main functional groups in the structure of lignins and condensed tannins. Methoxy groups are also abundant in lignins. Each group displays varying chemical reactivity within these biopolymers. Therefore, the selective and specific functionalization of lignins and condensed tannins can be achieved by understanding the chemistry behavior of these functional groups. Targeted applications include biomedicine, monomers and surface active agents for sustainable plastics.

Sunlight-sensitive carbon dots for plant immunity priming and pathogen defence

Global food production faces persistent threats from environmental challenges and pathogenic attacks, leading to significant yield losses. Conventional strategies to combat pathogens, such as fungicides and disease-resistant breeding, are limited by environmental contamination and emergence of pathogen resistance. Herein, we engineered sunlight-sensitive and biodegradable carbon dots (CDs) capable of generating reactive oxygen species (ROS), offering a novel and sustainable approach for plant protection. Our study demonstrates that CDs function as dual-purpose materials: priming plant immune responses and serving as broad-spectrum antifungal agents. Foliar application of CDs generated ROS under light, and the ROS could damage the plant cell wall and trigger cell wall-mediated immunity. Immune activation enhanced plant resistance against pathogens without compromising photosynthetic efficiency or yield. Specifically, spray treatment with CDs at 240 mg/L (2 mL per plant) reduced the incidence of grey mould in N. benthamiana and tomato leaves by 44% and 12%, respectively, and late blight in tomato leaves by 31%. Moreover, CDs (480 mg/L, 1 mL) combined with continuous sunlight irradiation (simulated by xenon lamp, 9.4 × 105 lux) showed a broad-spectrum antifungal activity. The inhibition ratios for mycelium growth were 66.5% for P. capsici, 8% for S. sclerotiorum and 100% for B. cinerea, respectively. Mechanistic studies revealed that CDs effectively inhibited mycelium growth by damaging hyphae and spore structures, thereby disrupting the propagation and vitality of pathogens. These findings suggest that CDs offer a promising, eco-friendly strategy for sustainable crop protection, with potential for practical agricultural applications that maintain crop yields and minimize environmental impact.

A translatable IR-chemometrics model for the rapid prediction of structural and material properties of technical lignins

Technical lignins are an industrial byproduct of plant biomass processing, for example, paper production or biorefinery operations. They are highly functional and aromatic, making them potentially suitable for a diverse range of applications; however, their exact structural composition depends on the plant species and the industrial process involved. A major bottleneck to lignin valorization and to biorefining in general is the equipment and time investment required for the full characterization of each sample. An array of wet chemical, spectroscopic, chromatographic and thermal methods are typically required to effectively characterize a given lignin sample. To ease the analytical burden, measured lignin properties can be correlated with detailed spectroscopic data obtained from a rapid analytical technique, such as attenuated total reflectance (ATR) Fourier-transform infrared (IR) spectroscopy, which requires minimal sample preparation. With sufficient sensitivity of the spectroscopic data, partial least squares regression models can be calibrated and, thus, predict these properties for future samples for which only the ATR-IR spectra are recorded. So far, several structural and macromolecular properties of lignin have been correlated with ATR-IR spectral data and quantitatively predicted in such a manner, including molecular weight, hydroxyl group content ([OH]), interunit linkage abundance and glass transition temperature. The protocol to apply this powerful lignin characterization methodology is described herein. Here, we also present a simple calibration transfer step, which when implemented before partial least squares regression, addresses the problem of instrument dependency. With the calibrated model, it is possible to determine lignin properties from a single ATR-IR spectral measurement (in ~5 min per sample).

Transcriptome response of the white-rot fungus Trametes versicolor to hybrid poplar exhibiting unique lignin chemistry

BACKGROUND

Production of biofuels and bioproducts from lignocellulosic material is limited due to the complexity of the cell wall structure. This necessitates the use of physical, chemical, and/or physico-chemical pretreatment technologies, which adds significant capital, operational, and environmental costs. Biological pretreatment strategies have the potential to mitigate these expenses by harnessing the innate ability of specialized bacteria and fungi to deconstruct lignocellulose. White-rot fungi (e.g. Trametes versicolor) have been shown to be effective at biological pretreatment of lignocellulose, yet it was uncertain if these fungi are feedstock agnostic or are able to sense subtle changes in cell wall chemistry.

RESULTS

The present study examined the transcriptome response by Trametes versicolor to transgenic hybrid poplar (Populus tremula × alba) lines with altered syringyl (S) and guaiacyl (G) lignin. Specifically, the transcriptional response of the fungus to wild-type wood was compared to that from the wood of six transgenic lines within three lignin phenotypes, LSX (low S with hydroxy-G), LSHG (low S with high G), and HS (high S), with 350 transcripts showing significant differences among the samples. The transcriptome of T. versicolor varied according to the lignin phenotype of the wood, with the LSX wood resulting in the most substantial changes in T. versicolor transcript abundance. Specifically, the LSX wood led to 50 upregulated and 48 downregulated transcripts from WT at the twofold or greater threshold. For example, transcripts for the lignin peroxidases LiP3 and LiP10 were downregulated (approximately 12X and 31X lower, respectively) by the fungus on LSX wood compared to wild-type wood. LSX wood also resulted in approximately 11X lower transcript numbers of endo-β-1,4-glucanase yet led to an increase in expression of certain hemicellulases, further highlighting the altered deconstruction strategy by the fungus on this wood type.

CONCLUSIONS

Overall, the results of this study demonstrated that T. versicolor was able to respond to transgenic poplar wood with the same genetic background, which has important implications for biological pretreatment strategies involving feedstocks that are genetically modified or have considerable natural variations in cell wall chemistry.

Urea treatment causes significant changes in microbial composition and associated metabolism of corn stover and rice straw

OBJECTIVE

Urea ammoniation is one of the more effective ways for straw feed utilization. Current research on urea ammoniation has focused on chemical reactions in the process of ammoniating straw, neglecting the microbial-driven process.

METHODS

This study aims to examine the effects of 2% and 4% urea on bacteria and fungi and their metabolites and fermentation quality of corn stover and rice straw under 40% and 60% moisture conditions.

RESULTS

Urea ammoniation at 4% increased the total nitrogen content of corn stover and rice straw, and reduced the neutral detergent fiber and acid detergent lignin of rice straw. Lactic acid and acetic acid are produced during the urea ammonification process, and 2% urea treatment has the best promoting effect on it. Urea ammoniation at 2% also modified the composition of the Lactobacillales and increased the relative abundance of Enterococcus of corn stover and rice straw under 60% water, leading to changes in the main driving microbiota. Moreover, urea ammoniation can promote the metabolism of bacteria and fungi in degrading lignin, producing various lignin degradation products, such as vanillin, 4-hydroxybenzaldehyde, protocatechuic acid, sinapyl alcohol, benzaldehyde, benzoic acid, etc.

CONCLUSION

Urea ammoniation is not only a chemical process, but also a microbial-driven process that involves changes in microbial composition and associated metabolism.

Crystal structure and functional characterization of a novel bacterial lignin-degrading dye-decolorizing peroxidase

A new gene coding for an iron-containing enzyme was identified in the genome of Acinetobacter radioresistens. Bioinformatics analysis allowed the assignment of the protein to DyP peroxidases, due to the presence of conserved residues involved in heme binding and catalysis. Moreover, Ar-DyP is located in an operon coding also for other enzymes involved in iron uptake and regulation. The crystal structure of Ar-DyP determined at 1.85 Å resolution shows that the heme pocket Ar-DyP is "wet" forming a continuous hydrogen-bond network that enables the communication between heme and distal residues. Moreover, as shown by the crystal structure and covalent crosslinking experiments, Ar-DyP uses a long-range electron transfer pathway involving His-181 and Tyr-241, in the active site and on the surface of the enzyme, respectively. This pathway allows oxidation of substrates of different sizes, including Kraft lignin. Indeed, the biochemical characterization showed that Ar-Dyp oxidizes ABTS and Reactive Blue 19 (turnover numbers of 500 and 464 min-1, respectively), but also phenolic compounds such as guaiacol and pyrogallol (turnover numbers of 7.4 and 1.8 min-1 respectively). Overall, the data shows that Ar-DyP is a promising candidate for applications in lignin valorization, bioremediation and industrial processes involving the breakdown of phenolic compounds.

A review on bioactivity, plant safety, and metal-reducing potential of lignin, its micro/nanostructures, and composites

Modern science focuses on sustainability-oriented innovation. Structurally sophisticated lignin is a sustainable alternative to non-renewable resources. Over the last several years, a tremendous scientific effort has been made to innovate lignin-based sustainable materials for numerous advanced applications. The lignin's phenolic, methoxyl and aliphatic hydroxyl functional groups are biologically and chemically active, making it conducive to developing state-of-the-art biomedicine, food packaging, crop protection, and catalyst materials. The biocidal effect of lignin rests on the phenolic compounds, specifically the double bond in α, β positions of the side chain, and a methyl group in the γ position. Also, depending on the biomass source and the pulping method, lignins possess different biocidal and antioxidant properties. The abundant hydroxyl groups in lignin are metal reductants and possess capping ability for the nanoparticles (NPs). This review focused on lignin's bioactivity mechanism, including antimicrobial efficacy and antioxidant properties. Lignin-based micro/nanocomposites and their application on food packaging, plant protection, and growth will also be explored. We will also review the application of lignin as a reducing and capping agent for the synthesis of metal NPs.

Pomegranate ATP-binding cassette transporter PgABCG9 plays a negative regulatory role in lignin accumulation

Seed hardness is an important quality characteristic of pomegranate fruit. The development of seed hardness relies on the deposition of lignin in the inner seed coat, but the underlying molecular mechanisms remain unclear. In this study, we identified a member of ABCG transporters, PgABCG9, which may function in seed hardening by negatively regulating lignin biosynthesis. PgABCG9 was expressed at high levels in the inner seed coats of pomegranate fruit, and its transcript level was negatively correlated with seed hardness. PgABCG9-transgenic Arabidopsis plants exhibited weaker growth and thinner stems than the wild-type. The number of xylem cells, xylem cell wall thickness, and lignin deposition in the PgABCG9 transgenic plants were significantly reduced. In addition, overexpression of PgABCG9 in Arabidopsis enhanced plant tolerance to exogenous monolignols. Targeted metabolite profiling revealed that the contents of metabolites involved in lignin biosynthesis, including monolignols and monolignol precursors, were also reduced in PgABCG9- transgenic plants. We found that PgABCG9 is localized to the Golgi. These findings indicate that PgABCG9 plays a negative regulatory role in lignin biosynthesis and potentially contributes to soft-seed development in pomegranate through a mechanism that includes the reduction of lignin content in the seed coat by sequestration of monolignols in intracellular compartments.

Deep transcriptome and metabolome analysis to dissect untapped spatial dynamics of specialized metabolism in Saussurea costus (Falc.) Lipsch

Saussurea costus (Falc.) is an endangered medicinal plant possessing diverse phytochemical compounds with clinical significance and used to treat numerous human ailments. Despite the source of enriched phytochemicals, molecular insights into spatialized metabolism are poorly understood in S. costus. This study investigated the dynamics of organ-specific secondary metabolite biosynthesis using deep transcriptome sequencing and high-throughput UHPLC-QTOF based untargeted metabolomic profiling. A de novo assembly from quality reads fetched 59,725 transcripts with structural (53.02%) and functional (66.13%) annotations of non-redundant transcripts. Of the 7,683 predicted gene families, 3,211 were categorized as 'single gene families'. Interestingly, out of the 4,664 core gene families within the Asterids, 4,560 families were captured in S. costus. Organ-specific differential gene expression analysis revealed significant variations between leaves vs. stems (23,102 transcripts), leaves vs. roots (30,590 transcripts), and roots vs. stems (21,759 transcripts). Like-wise, putative metabolites (PMs) were recorded with significant differences in leaves vs. roots (250 PMs), leaves vs. stem (350 PMs), and roots vs. stem (107 PMs). The integrative transcriptomic and metabolomic analysis identified organ-specific differences in the accumulation of important metabolites, including secologanin, menthofuran, taraxerol, lupeol, acetyleugenol, scopoletin, costunolide, and dehydrocostus lactone. Furthermore, a global gene co-expression network (GCN) identified putative regulators controlling the expression of key target genes of secondary metabolite pathways including terpenoid, phenylpropanoid, and flavonoid. The comprehensive functionally relevant genomic resource created here provides beneficial insights for upscaling targeted metabolite biosynthesis through genetic engineering, and for expediting association mapping efforts to elucidate the casual genetic elements controlling specific bioactive metabolites.

Design and Synthesis of Thioglycosylated Monolignol Dual Probes for Bioimaging of Lignin Biosynthesis

Lignin biosynthesis is a critical process that underpins plant structural integrity and defenses. Central to this pathway are monolignol glucosides (MLGs), whose role as intermediates remains debated. To elucidate MLGs' involvement, we developed thioglycosylated monolignol probes compatible with click chemistry for in situ visualization of lignin biosynthesis. Using a highly selective Buchwald-Hartwig-Migita cross-coupling approach, these probes incorporate glycosyl thiols into MLGs, creating stable thioacetal bonds to enhance both metabolic stability and tracking precision. The unique chemistry of these probes allows for incorporation within the lignification pathway, enabling specific visualization of MLG involvement in lignin formation. The probes are compatible with bioorthogonal chemistry labeling and confocal microscopy, allowing detailed tracking of MLG transport, storage, and incorporation into cell walls. Our findings provide new insights into lignification dynamics, underscoring the metabolic roles of MLGs and demonstrating their potential as metabolic intermediates in lignin polymerization. This approach offers a novel chemical biology toolset to dissect plant cell wall biosynthesis and will help elucidatethe molecular roles of MLGs in the context of plant biochemistry and resilience.

Lignin activation with selected ionic liquids based on kinetic and thermodynamic analyses

Herein, the potential of lignin activation with selected ionic liquids (ILs) was investigated to enhance the usefulness of lignin in materials science and electrochemical systems. The main objective was to increase the carbonyl content in lignin through selective oxidation, which would enable its use as a sustainable alternative, for example, in electrode materials and composite systems. Using ILs as activators, the modification process focused on maintaining the structural integrity of lignin while increasing its functional group profile. The research included the precise control of air supply as the oxidant and regulation of the process temperature to prevent lignin depolymerization. Advanced kinetic and thermodynamic analyses of thermal decomposition were performed using thermogravimetric analysis, differential thermogravimetric analysis, and differential thermal analysis, with kinetic modeling based on the Coats-Redfern method. These methodologies facilitated a detailed understanding of the thermal stability, degradation kinetics, and reactivity of the material. Results revealed that the activation of lignin with ILs significantly increases the carbonyl (quinone) group content, enhancing its potential as a reversible proton and electron acceptor in electrochemical applications. The study highlights the importance of balancing degradation kinetics and structural properties of lignin to optimize its reactivity and functional performance. Mechanisms such as F1 and D4 effectively describe the degradation process, with the activation energy (Ea) ranging from 66.691 to 309.389 kJ/mol. The enthalpy (ΔH) ranges from 62.488 to 302.950 kJ/mol, while the ΔS values, both positive and negative, reflect the heterogeneity of the reaction depending on the system and ionic liquid conditions.

A Review of Biochar from Biomass and Its Interaction with Microbes: Enhancing Soil Quality and Crop Yield in Brassica Cultivation

Biochar, produced from biomass, has become recognized as a sustainable soil amendment that has the potential to improve soil quality and agricultural production. This review focuses on production processes and properties of biochar derived from different types of biomass, including the synergistic interactions between biochar and soil microorganisms, emphasizing their influence on overall soil quality and crop production, particularly in cultivation of Brassica crops. It additionally addresses the potential benefits and limitations of biochar and microbial application. Biomass is a renewable and abundant resource and can be converted through pyrolysis into biochar, which has high porosity, abundant surface functionalities, and the capacity to retain nutrients. These characteristics provide optimal conditions for beneficial microbial communities that increase nutrient cycling, reduce pathogens, and improve soil structure. The information indicates that the use of biochar in Brassica crops can result in improved plant growth, yield, nutrient uptake, and stress mitigation. This review includes information about biochar properties such as pH, elemental composition, ash content, and yield, which can be affected by the different types of biomass used as well as pyrolysis conditions like temperature. Understanding these variables is essential for optimizing biochar for agricultural use. Moreover, the information on the limitations of biochar and microbes emphasizes the importance of their benefits with potential constraints. Therefore, sustainable agriculture methods can possibly be achieved by integrating biochar with microbial management measurements, resulting in higher productivity and adaptability in Brassica or other plant crop cultivation systems. This review aims to provide a comprehensive understanding of biochar's role in supporting sustainable Brassica farming and its potential to address contemporary agricultural challenges.

PbMADS49 Regulates Lignification During Stone Cell Development in 'Dangshansuli' (Pyrus bretschneideri) Fruit

Lignified stone cell content is one of the critical factors affecting 'Dangshansuli' fruit quality. The function of MADS-box transcription factors in regulating lignin biosynthesis in pear fruit is still less. In this study, PbMADS49 gene silencing inhibited the lignin biosynthesis and stone cell secondary wall development of pear fruit mainly through reducing the expression levels of lignin monomer polymerisation key enzymes (PbPRX33 and PbPRX45). PbMADS49 was a transcriptional repressor inhibiting its transcription by binding to the CArG element in the target gene promoter. Combined with the co-expression network and promoter cis-acting element analysis, we hypothesised that PbMADS49 positively regulates the transcription of PbPRX33 through PbWRKY63. The gene silencing effect of homologous genes PbPRX33-1 and PbPRX33-2 was consistent with PbMADS49, and PbPRX33-2 was more significant than PbPRX33-1. This study shows that PbMADS49 is a positive regulator of stone cell lignification, providing new insights into the development mechanism of pear stone cells.

Identification and characterization of the auxin-response factor family in moso bamboo reveals that PeARF41 negatively regulates second cell wall formation

Auxin response factors (ARFs) are key transcriptional factors mediating the transcriptional of auxin-related genes that play crucial roles in a range of plant metabolic activities. The characteristics of 47 PeARFs, identified in moso bamboo and divided into three classes, were evaluated. Structural feature analysis showed that intron numbers ranged from 3 to 14, while Motif 1, 2, 7 and 10 were highly conserved, altogether forming DNA-binding and ARF domains. Analysis of RNA-seq from different tissues revealed that PeARFs showed tissue-specificity. Additionally, abundant hormone-response and stress-related elements were enriched in promoters of PeARFs, supporting the hypothesis that the expression of PeARFs was significantly activated or inhibited by ABA and cold treatments. Further, PeARF41 overexpression inhibited SCW formation by reducing hemicellulose, cellulose and lignin contents. Moreover, a co-expression network, containing 28 genes with PeARF41 at its core was predicted, and the results of yeast one hybridization (Y1H), electrophoretic mobility shift assay (EMSA) and dual-luciferase (Dul-LUC) assays showed that PeARF41 bound the PeSME1 promoter to inhibit its expression. We conclude that a 'PeARF41-PeSME1' regulatory cascade mediates SCW formation. Our findings provided a solid theoretical foundation for further research on the role of PeARFs.

Exploration of low-sulfonate lignin electrospinning conditions for the development of new renewable lubricant formulations

This study explores the preparation of lubricating oleo-dispersions using electrospun nanofibrous mats made from low-sulfonate lignin (LSL) and polycaprolactone (PCL). The rheological and tribological properties of the oleo-dispersions were significantly modulated for the first time through the exploration of LSL/PCL ratio and electrospinning conditions such as applied voltage, distance between the tip and collector, flow rate, ambient humidity, and collector configuration. Adequate uniform ultrathin fibers and Small-amplitude oscillatory shear (SAOS) functions of the oleo-dispersions, with storage modulus values ranging from 102 to 105 Pa at 25 °C, were obtained with a flow rate of 0.5 ml h-1, an applied voltage of 15 kV, relative humidity 45% and a static collector. The LSL/PCL ratio directly affected the mechanical properties of the membranes, influencing stiffness and wear resistance. Higher PCL content enhanced membrane stiffness, reflected in increased SAOS values, but also led to higher friction coefficients (from 0.11 to 0.18) and more pronounced wear traces (measured by wear diameter: 440 to 860 μm). These interactions underscore the complex relationship between micro- and/or nano-structures and tribological performance. This study establishes a clear link between electrospinning conditions and the performance of oleo-dispersions, offering a versatile platform for the development of customizable, renewable lubricants. These findings contribute to the advancement of sustainable lubrication technologies, demonstrating the potential of tailor-made oleo-dispersions as alternatives to traditional lubricants.

Engineering yeast to produce fraxetin from ferulic acid and lignin

Lignin, the most abundant renewable source of aromatic compounds on earth, remains underexploited in traditional biorefining. Fraxetin, a naturally occurring flavonoid, has garnered considerable attention in the scientific community due to its diverse and potent biological activities such as antimicrobial, anticancer, antioxidant, anti-inflammatory, and neurological protective actions. To enhance the green and value-added utilization of lignin, Saccharomyces cerevisiae was engineered as a cell factory to transform lignin derivatives to produce fraxetin. The expression of scopoletin 8-hydroxylase (S8H) and coumarin synthase (COSY) enabled S. cerevisiae to produce fraxetin from ferulic acid, one of the three principal monomers. The optimized fermentation strategies produced 19.1 mg/L fraxetin from ferulic acid by engineered S. cerevisiae. Additionally, the engineered cell factory achieved a fraxetin titer of 7.7 mg/L in lignin hydrolysate. This study successfully demonstrates the biotransformation of lignin monomers and lignin hydrolysate into fraxetin using a S. cerevisiae cell factory, thereby providing a viable strategy for the valorization of lignin. KEY POINTS: • AtS8H showed substance specificity in the hydroxylation of scopoletin. • AtCOSY and AtS8H were key enzymes for converting ferulic acid into fraxetin. • Yeast was engineered to produce fraxetin from lignin hydrolysate.

Advances in L-Lactic Acid Production from Lignocellulose Using Genetically Modified Microbial Systems

Lactic acid is a vital organic acid with a wide range of industrial applications, particularly in the food, pharmaceutical, cosmetic, and biomedical sectors. The conventional production of lactic acid from refined sugars poses high costs and significant environmental impacts, leading to the exploration of alternative raw materials and more sustainable processes. Lignocellulosic biomass, particularly agro-industrial residues such as agave bagasse, represents a promising substrate for lactic acid production. Agave bagasse, a by-product of the tequila and mezcal industries, is rich in fermentable carbohydrates, making it an ideal raw material for biotechnological processes. The use of lactic acid bacteria (LAB), particularly genetically modified microorganisms (GMMs), has been shown to enhance fermentation efficiency and lactic acid yield. This review explores the potential of lignocellulosic biomass as a substrate for microbial fermentation to produce lactic acid and other high-value products. It covers the composition and pretreatment of some agricultural residues, the selection of suitable microorganisms, and the optimization of fermentation conditions. The paper highlights the promising future of agro-industrial residue valorization through biotechnological processes and the sustainable production of lactic acid as an alternative to conventional methods.

Fruit-specific effects of tryptophan and melatonin as active components to extend the functionality of red fruits during post-harvest processing

Preserving quality attributes in the distribution chain is a challenging task, particularly in fruits with a brief shelf life. The application of melatonin in cherries, raspberries, strawberries and blueberries stored at room temperature was evaluated, as well as the effects of its precursor (tryptophan) to determine their specificity and interchangeable feasibility for post-harvest applications. The results demonstrated that melatonin is effective in all tested fruits, reducing deterioration rate and its severity, preserving fruit firmness and reducing darkening and weight loss. Furthermore, tryptophan applications incremented melatonin contents in strawberries and blueberries and delayed decay in both fruits. Melatonin reduced postharvest losses in all studied fruits related to its antisenescent properties, while the beneficial impact of tryptophan in extending shelf life was fruit-specific and appeared to be partly mediated by melatonin. Melatonin and tryptophan must be considered as active components of new formulations for extending the shelf life of red fruits during post-harvest processing.

Mitogen-activated protein kinase-mediated regulation of plant specialized metabolism

Post-transcriptional and post-translational modification of transcription factors (TFs) and pathway enzymes significantly affect the stress-stimulated biosynthesis of specialized metabolites (SMs). Protein phosphorylation is one of the conserved and ancient mechanisms that critically influences many biological processes including specialized metabolism. The phosphorylation of TFs and enzymes by protein kinases (PKs), especially the mitogen-activated protein kinases (MAPKs), is well studied in plants. While the roles of MAPKs in plant growth and development, phytohormone signaling, and immunity are well elucidated, significant recent advances have also been made in understanding the involvement of MAPKs in specialized metabolism. However, a comprehensive review highlighting the significant progress in the past several years is notably missing. This review focuses on MAPK-mediated regulation of several important SMs, including phenylpropanoids (flavonoids and lignin), terpenoids (artemisinin and other terpenoids), alkaloids (terpenoid indole alkaloids and nicotine), and other nitrogen- and sulfur-containing SMs (camalexin and indole glucosinolates). In addition to MAPKs, other PKs also regulate SM biosynthesis. For comparison, we briefly discuss the regulation by other PKs, such as sucrose non-fermenting-1 (SNF)-related protein kinases (SnRKs) and calcium-dependent protein kinases (CPKs). Furthermore, we provide future perspectives in this active area of research.

Resistance of Populus davidiana × P. bolleana overexpressing cinnamoyl-CoA reductase gene to Lymantria dispar larvae

Lignin is a crucial defense phytochemical against phytophagous insects. Cinnamoyl-CoA reductase (CCR) is a key enzyme in lignin biosynthesis. In this study, transgenic Populus davidiana × P. bolleana overexpressing the PdbCCR gene were generated via Agrobacterium-mediated transformation. Successful integration of PdbCCR into the poplar genome was confirmed by PCR amplification and quantitative reverse transcription PCR (qRT-PCR). The lignin content in the transgenic poplar leaves was significantly higher than that in the wild poplar, and after L. dispar larvae fed on the transgenic poplar, the CCR activity was clearly induced. The L. dispar larvae grew slowly after feeding on transgenic poplar and the laccase, cellulase and three detoxifying enzymes were induced compared with larvae after feeding on wild-type poplar. The bioassay further revealed that transgenic poplar plants overexpressing PdbCCR showed a high level of resistance to L. dispar larvae. These results confirmed that PdbCCR is a candidate gene for breeding insect resistant poplar.

Electrospinning of cellulose nanocrystals; procedure and optimization

Cellulose nanocrystals (CNCs) and cellulose microfibrils (CMFs) are promising materials with the potential to significantly enhance the mechanical properties of electrospun nanofibers. However, the crucial aspect of optimizing their integration into these nanofibers remains a challenge. In this work, we present a method to prepare and electrospin a cellulosic solution, aiming to overcome the existing challenges and realize the optimized incorporation of CNCs into nanofibers. The solution parameters of electrospinning were explored using a combined experimental and simulation (molecular dynamics) approach. Experimental results emphasize the impact of polymer solution concentration on fiber morphology, reinforcing the need for further optimization. Simulations highlight the intricate factors, including the molecular weight of cellulose acetate (CA) polymer chains, electrostatic fields, and humidity, that impact the alignment of CNCs and CMFs. Furthermore, efforts were made to study CNCs/CMFs alignment rate and quality optimization. It is predicted that pure CNCs benefit more from electrostatic alignment, while lower molecular weight CA enables better CNC/CMF alignment.

Effects of Silicon Concentration and Synthesis Duration on Lignin Structure: A Spectroscopic and Microscopic Study

Silicon (Si) is a highly abundant mineral in Earth's crust. It plays a vital role in plant growth, providing mechanical support, enhancing grain yield, facilitating mineral nutrition, and aiding stress response mechanisms. The intricate relationship between silicification and lignin chemistry significantly impacts cell wall structure. Yet, the precise influence of Si on lignin synthesis remains elusive. This study investigated the interaction between Si and lignin model compounds during in vitro synthesis. Employing spectroscopic and microscopic analyses, we delineated how Si concentrations modulate lignin polymerization dynamics, particularly affecting molecular conformation and aggregation behavior over time. Fluctuations in the polymer structure are directly related to both the synthesis time and the concentration of silica. Our results demonstrate that lower Si concentrations promote the aggregation of lignin oligomers into larger particles, while higher concentrations increase the possibility of oligomer repulsion, thus preventing particle growth. These findings elucidate the intricate interplay between Si and lignin, which is crucial for understanding plant cell wall structure and stress resilience. Moreover, the results provide insights for developing lignin-silica materials with increasing applications in industry and medicine.

Systematic characterization of cinnamyl alcohol dehydrogenase members revealed classification and function divergence in Haplomitrium mnioides

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) is considered to be a key enzyme in lignin biosynthesis, which can catalyze cinnamyl aldehyde to produce cinnamyl alcohol. In this study, three putative CADs were characterized from the liverwort Haplomitrium mnioides. The sequence alignment and phylogenetic analysis revealed that HmCADs belonged to a multigene family, with three HmCADs belonging to class II, class III, and class IV, respectively. In vitro enzymatic studies demonstrated that HmCAD2 exhibited high affinity and catalytic activity towards five cinnamyl aldehydes, followed by HmCAD3 with poor catalytic activity, and HmCAD1 catalyzed only the reaction of p-coumaryl aldehyde and coniferyl aldehyde with extremely low catalytic capacity. Protein-substrate binding simulations were performed to investigate the differences in catalytic activity exhibited when proteins catalyzed different substrates. Furthermore, distinct expression patterns of three HmCADs were identified in different plant tissues. Subcellular localization tests confirmed that HmCAD1/2/3 was located in the cytoplasm. The simulated responses of HmCADs to different stresses showed that HmCAD1 played a positive role in coping with each stress, while HmCAD2/3 was weak. These findings demonstrate the diversity of CADs in liverwort, highlight the divergent role of HmCAD1/2/3 in substrate catalysis, and also suggest their possible involvement in stress response, thereby providing new insights into CAD evolution while emphasizing their potential distinctive and collaborative contributions to the normal growth of primitive liverworts.

Advances in understanding dietary fiber: Classification, structural characterization, modification, and gut microbiome interactions

Gut microbiota and their metabolites profoundly impact host physiology. Targeted modulation of gut microbiota has been a long-term interest in the scientific community. Numerous studies have investigated the feasibility of utilizing dietary fibers (DFs) to modulate gut microbiota and promote the production of health-beneficial bacterial metabolites. However, the complexity of fiber structures, microbiota composition, and their dynamic interactions have hindered the precise prediction of the impact of DF on the gut microbiome. We address this issue with a new perspective, focusing on the inherent chemical and structural complexity of DFs and their interaction with gut microbiota. The chemical and structural complexity of fibers was thoroughly elaborated, encompassing the fibers' molecular composition, polymorphism, mesoscopic structures, porosity, and particle size. Advanced characterization techniques to investigate fiber structural properties were discussed. Additionally, we examined the interactions between DFs and gut microbiota. Finally, we summarized processing techniques to modify fiber structures for improving the fermentability of DF by gut microbiota. The structure of fibers, such as their crystallinity, porosity, degree of branching, and pore wettability, significantly impacts their interactions with gut microbiota. These structural differences also substantially affect fiber's fermentability and capability to modulate the composition of gut microbiota. Conventional approaches are not capable of investigating complex fiber properties and their influences on the gut microbiome; therefore, it is of the essence to involve advanced material characterization techniques and artificial intelligence to unveil more comprehensive information on this topic.

Ontogenetic differences in sun and shade galls of Clinodiplosis profusa on Eugenia uniflora leaves and the cytological antioxidant mechanisms in gall cells

The gall-host Eugenia uniflora (Myrtaceae) is adaptable to different light conditions, enabling leaf production and survival in both sun and shade. Leaves of E. uniflora in shaded environments have more mesophyll layers, and galls of Clinodiplosis profusa (Cecidomyiidae) are larger and wider. Based on these previous observations, this study investigated the morphogenesis of galls induced by C. profusa on leaves of E. uniflora in different light conditions, revealing if the galls have a potential for acclimation, as observed with leaves. For this purpose, we compared the anatomical, histometric, and histochemical development of leaves and galls at different stages of development in sun and shade environments. Additionally, we analyzed the cytological features of the tissues composing the mature gall walls. Cells of shade galls expanded more toward the end of the developmental phase, which may explain the larger volume found for shade galls in a previous study. However, during the mature phase, these galls showed no significant differences in tissue thickness and final cell elongation in the contrasting light conditions. In the ultrastructural analyses, mature galls showed a gradient distinguishing the outer and inner parenchyma cells. The inner parenchyma had nutritive cells, with dense cytoplasm and abundant organelles. A higher accumulation of starch grains in nutritive cells, with evidence of hydrolysis of starch grains detected in the innermost layers leads to the accumulation of reducing sugars, which, with the presence of plastoglobules and protein bodies, are important mechanisms of oxidative stress dissipation in the cells in contact with the gall inducer.

Characteristic study of Candida rugosa lipase immobilized on lignocellulosic wastes: effect of support material

For the first time is reported the comparison of solid biocatalysts derived from Candida rugosa lipase (CRL) immobilized on different lignocellulosic wastes (rice husk, brewer's spent grain, hemp tea waste, green tea waste, vine bark, and spent coffee grounds) focusing on the characterization of these materials and their impact on the lipase-support interaction. The wastes were subjected to meticulous characterization by ATR-FTIR, BET, and SEM analysis, besides lignin content and hydrophobicity determination. Investigating parameters influencing immobilization performance revealed the importance of morphology, textural properties, and hydrophobic interactions revealed the importance of morphology, textural properties and especially hydrophobic interactions which resulted in positive correlations between surface hydrophobicity and lipase immobilization efficiency. Hemp tea waste and spent coffee grounds demonstrated superior immobilization performances (7.20 U/g and 8.74 U/g immobilized activity, 102.3% and 33.5% efficiency, 13.4% and 15.4% recovery, respectively). Moreover, they demonstrated good temporal stability (100% and 92% residual activity after 120 days, respectively) and retained 100% of their immobilized activity after five reuses in the hydrolysis of p-nitrophenyl palmitate in hexane. In addition, the study of enzymatic desorption caused by ionic strength and detergent treatments indicated mixed hydrophobic and electrostatic interactions in rice husk, vine bark, and spent coffee grounds supports, while hemp tea waste and green tea waste were dominated by hydrophobic interactions.

Arabidopsis 3-Deoxy-d-Arabino-Heptulosonate 7-Phosphate (DAHP) Synthases of the Shikimate Pathway Display Both Manganese- and Cobalt-Dependent Activities

The plant shikimate pathway directs a significant portion of photosynthetically assimilated carbon into the downstream biosynthetic pathways of aromatic amino acids (AAA) and aromatic natural products. 3-Deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase (hereafter DHS) catalyzes the first step of the shikimate pathway, playing a critical role in controlling the carbon flux from central carbon metabolism into the AAA biosynthesis. Previous biochemical studies suggested the presence of manganese- and cobalt-dependent DHS enzymes (DHS-Mn and DHS-Co, respectively) in various plant species. Unlike well-studied DHS-Mn, however, the identity of DHS-Co is still unknown. Here, we show that all three DHS isoforms of Arabidopsis thaliana exhibit both DHS-Mn and DHS-Co activities in vitro. A phylogenetic analysis of various DHS orthologs and related sequences showed that Arabidopsis 3-deoxy-D-manno-octulosonate-8-phosphate synthase (KDOPS) proteins were closely related to microbial Type I DHSs. Despite their sequence similarity, these Arabidopsis KDOPS proteins showed no DHS activity. Meanwhile, optimization of the DHS assay conditions led to the successful detection of DHS-Co activity from Arabidopsis DHS recombinant proteins. Compared with DHS-Mn, DHS-Co activity displayed the same redox dependency but distinct optimal pH and cofactor sensitivity. Our work provides biochemical evidence that the DHS isoforms of Arabidopsis possess DHS-Co activity.

ShF5H1 overexpression increases syringyl lignin and improves saccharification in sugarcane leaves

The agricultural sugarcane residues, bagasse and straws, can be used for second-generation ethanol (2GE) production by the cellulose conversion into glucose (saccharification). However, the lignin content negatively impacts the saccharification process. This polymer is mainly composed of guaiacyl (G), hydroxyphenyl (H), and syringyl (S) units, the latter formed in the ferulate 5-hydroxylase (F5H) branch of the lignin biosynthesis pathway. We have generated transgenic lines overexpressing ShF5H1 under the control of the C4H (cinnamate 4-hydroxylase) rice promoter, which led to a significant increase of up to 160% in the S/G ratio and 63% in the saccharification efficiency in leaves. Nevertheless, the content of lignin was unchanged in this organ. In culms, neither the S/G ratio nor sucrose accumulation was altered, suggesting that ShF5H1 overexpression would not affect first-generation ethanol production. Interestingly, the bagasse showed a significantly higher fiber content. Our results indicate that the tissue-specific manipulation of the biosynthetic branch leading to S unit formation is industrially advantageous and has established a foundation for further studies aiming at refining lignin modifications. Thus, the ShF5H1 overexpression in sugarcane emerges as an efficient strategy to improve 2GE production from straw.

Exploring the mechanism of seed shattering in Psathyrostachys juncea through histological analysis and comparative transcriptomics

BACKGROUND

Seed shattering (SS) negatively impacts seed yield in Psathyrostachys juncea. Understanding and improving the SS trait requires elucidating the regulatory mechanisms of SS and identifying the key genes involved.

RESULTS

This study presents a comprehensive analysis of the abscission zone (AZ) structures at four developmental stages in two P. juncea genotypes. High-SS P. juncea (H) exhibited a significantly higher SS rate than low-SS P. juncea (L) at all four developmental stages. Anatomical analysis revealed that the degree of lignification in the AZ cell walls is related to the integrity of the abscission structure. The degradation of the AZ in H occurred earlier and was more severe compared to L. At different developmental stages of the AZ, H exhibited higher cellulase and polygalacturonase activities and higher abscisic acid contents compared to L. Conversely, L showed higher lignin, cytokinin, auxin, and gibberellin contents than H. Transcriptomic analysis identified key metabolic pathways related to SS in P. juncea, such as phenylpropanoid biosynthesis, fructose and mannose metabolism, galactose metabolism, and pentose and glucuronate interconversions. The integration of morphological, histological, physiochemical, and metabolic data led to the identification of critical genes, including AUX1, CKX, ABF, GH3, 4CL, CCoAOMT, BGAL, Gal, and PG. The roles of these genes were involved in the regulation of plant hormones and in the synthesis and degradation of cell walls within the AZ.

CONCLUSIONS

This study provides an in-depth understanding of the regulatory mechanisms of SS in P. juncea through comparative transcriptomic analysis. The SS in P. juncea may result from the degradation of the cell wall regulated by cell wall hydrolases genes. The genes identified in this study provide a basis for the genetic improvement of SS traits and serve as a reference for research on other grass species.

New Insight into Industrial Lignin Intermolecular Force Heterogeneity Mitigation: Monodispersed Lignin Colloidal Sphere Synthesis and Full Biomass Photonic Material Preparation

Industrial lignin is an underutilized resource from the pulping industry due to its high heterogeneity. The transformation of industrial lignin into monodispersed lignin colloidal spheres (LCSs) for the preparation of advanced biomass photonic materials is particularly appealing, because of their unique biocompatibility. However, the LCSs synthesized from industrial lignin generally show a wide size distribution and thus limit this specific application. To address the issue, selective functionalization was carried out to convert phenolic and aliphatic -OH groups into ester groups, decreasing the LCS size distribution to a monodispersing degree. Simulation analysis revealed that the functionalization had narrowed the difference of C-O linkage electron cloud distribution and led to a lignin polarity decrease. Additionally, atomic force microscopy (AFM) quantification of lignin proved a force distribution index (FDI) decrease from 0.38 to 0.11, which was consistent with the LCS polymer dispersity index (PDI) decrease from 0.182 to 0.05. The photonic materials can be readily prepared from monodispersed LCSs with the color precisely adjusted by controlling LCS particle sizes.

Lignin deoxygenation for the production of sustainable aviation fuel blendstocks

Lignin is an abundant source of renewable aromatics that has long been targeted for valorization. Traditionally, the inherent heterogeneity and reactivity of lignin has relegated it to direct combustion, but its higher energy density compared with polysaccharides makes it an ideal candidate for biofuel production. This Review critically assesses lignin's potential as a substrate for sustainable aviation fuel blendstocks. Lignin can generate the necessary cyclic compounds for a fully renewable, sustainable aviation fuel when integrated with current paraffinic blends and can meet the current demand 2.5 times over. Using an energy-centric analysis, we show that lignin conversion technologies have the near-term potential to match the enthalpic yields of existing commercial sustainable aviation fuel production processes. Key factors influencing the viability of technologies for converting lignin to sustainable aviation fuel include lignin structure, delignification extent, depolymerization performance, and the development of stable and tunable deoxygenation catalysts.

Peanut Shell Extract Improves Markers of Glucose Homeostasis in Diabetic Mice by Modulating Gut Dysbiosis and Suppressing Inflammatory Immune Response

BACKGROUND/OBJECTIVE

There is strong evidence that the tripartite interaction between glucose homeostasis, gut microbiota, and the host immune system plays a critical role in the pathophysiology of type 2 diabetes mellitus (T2DM). We reported previously that peanut shell extract (PSE) improves mitochondrial function in db/db mice by suppressing oxidative stress and inflammation in the liver, brain, and white adipose tissue. This study evaluated the impacts of PSE supplementation on glucose homeostasis, liver histology, intestinal microbiome composition, and the innate immune response in diabetic mice.

METHODS

Fourteen db/db mice were randomly assigned to a diabetic group (DM, AIN-93G diet) and a PSE group (1% wt/wt PSE in the AIN-93G diet) for 5 weeks. Six C57BL/6J mice received the AIN-93G diet for 5 weeks (control group). Parameters of glucose homeostasis included serum insulin, HOMA-IR, HOMA-B, and the analysis of pancreatic tissues for insulin and glucagon. We assessed the innate immune response in the colon and liver using a microarray. Gut microbiome composition of cecal contents was analyzed using 16S rRNA gene amplicon sequencing.

RESULTS

PSE supplementation improved glucose homeostasis (decreased serum insulin concentration, HOMA-IR, and HOMA-B) and reduced hepatic lipidosis in diabetic mice. PSE supplementation reversed DM-induced shifts in the relative abundance of amplicon sequence variants of Enterorhabdus, Staphylococcus, Anaerotruncus, and Akkermansia. Relative to the DM mice, the PSE group had suppressed gene expression levels of Cd8α, Csf2, and Irf23 and increased expression levels of Tyk2, Myd88, and Gusb in the liver.

CONCLUSIONS

This study demonstrates that PSE supplementation improves T2DM-associated disorders of diabetic mice, in part due to the suppression of innate immune inflammation.

Fungal community dynamics in a hyper-arid ecosystem after 7 and 47 years of petroleum contamination

This study investigates the impact of crude oil contamination on the fungal community dynamics in the Evrona Nature Reserve, situated in Israel's hyper-arid Arava Valley. The reserve experienced petroleum-hydrocarbon-spill pollution at two neighboring sites in 1975 and 2014. The initial contamination was left untreated, providing a unique opportunity to compare its effects to those of the second contamination event. In 2022, soil samples were collected from both contaminated areas and nearby clean (control) sites, 47 and 7 years after the spills. The taxonomic diversity of fungal community and functional guilds, as well as various properties of the soil, were analyzed. We focused on three functional groups within fungal communities: saprotrophs, symbiotrophs, and pathotrophs. The results revealed a significant decrease in number of fungal species in the contaminated samples over time. Consequently, prolonged effect of crude oil-contaminated soils can facilitate the development of a distinct fungal community, which has adapted to the conditions of oil contamination. This study aims to elucidate the dynamics of fungal communities in oil-contaminated soils, contributing to a better understanding of their behavior and adaptation in such environments.

Evolution of aromatic amino acid metabolism in plants: a key driving force behind plant chemical diversity in aromatic natural products

A diverse array of plant aromatic compounds contributes to the tremendous chemical diversity in the plant kingdom that cannot be seen in microbes or animals. Such chemodiversity of aromatic natural products has emerged, occasionally in a lineage-specific manner, to adopt to challenging environmental niches, as various aromatic specialized metabolites play indispensable roles in plant development and stress responses (e.g. lignin, phytohormones, pigments and defence compounds). These aromatic natural products are synthesized from aromatic amino acids (AAAs), l-tyrosine, l-phenylalanine and l-tryptophan. While amino acid metabolism is generally assumed to be conserved between animals, microbes and plants, recent phylogenomic, biochemical and metabolomic studies have revealed the diversity of the AAA metabolism that supports efficient carbon allocation to downstream biosynthetic pathways of AAA-derived metabolites in plants. This review showcases the intra- and inter-kingdom diversification and origin of committed enzymes involved in plant AAA biosynthesis and catabolism and their potential application as genetic tools for plant metabolic engineering. I also discuss evolutionary trends in the diversification of plant AAA metabolism that expands the chemical diversity of AAA-derived aromatic natural products in plants. This article is part of the theme issue 'The evolution of plant metabolism'.

Computational study on the impact of linkage sequence on the structure and dynamics of lignin

Lignin, one of the most abundant biopolymers on Earth, is of great research interest due to its industrial applications including biofuel production and materials science. The structural composition of lignin plays an important role in shaping its properties and functionalities. Notably, lignin exhibits substantial compositional diversity, which varies not only between different plant species but even within the same plant. Currently, it is unclear to what extent this compositional diversity plays on the overall structure and dynamics of lignin. To address this question, this paper reports on the development of two models of lignin containing all guaiacyl (G) subunits with varied linkage sequences and makes use of all-atom molecular dynamics simulations to examine the impact of linkage sequence alone on the lignin's structure and dynamics. This work demonstrates that the structure of the lignin polymer depends on its linkage sequence at temperatures above and below the glass transition temperature ( T g ), but the polymers exhibit similar structural properties as it is approaching the viscous flow state (480 K). At low temperatures, both of lignin models have a local dynamics confined in a cage, but the size of cages varies depending on structural differences. Interestingly, at temperatures higher than T g , the different linkage sequence leads to the subtle dynamical difference which diminishes at 480 K.

A review of lignin application in hydrogel dressing

Lignin is the most abundant natural aromatic polymer in the world. Currently, researchers have developed a number of lignin-based composite materials that are widely used in various fields, including industry, agriculture and medicine. Especially in recent years, lignin has attracted great interest as a high-value product for biomedical applications. Due to its antioxidant, antibacterial, adhesive and other properties, lignin is a promising candidate for the development of hydrogel dressings. However, there is no comprehensive overview of the application of lignin-based hydrogel dressings. In this review, lignin-based hydrogel skin dressings were first presented, and the preparation methods of physical and chemical crosslinking in lignin-based hydrogel dressings were discussed. In addition, various functional and environmentally responsive lignin-based hydrogel dressings were primarily reviewed. Finally, the prospects for the development of novel multifunctional lignin-based hydrogel dressings in the future were presented. In conclusion, this review provided a timely and comprehensive summary of the latest advances in the use of lignin as a biomaterial for hydrogel dressings, which would provide valuable guidance for the further development of lignin-based hydrogels.

Lignin hydrogenolysis: Tuning the reaction by lignin chemistry

Replacing fossil resource with biomass is one of the promising approaches to reduce our carbon footprint. Lignin is one of the three major components of lignocellulosic biomass, accounting for 10-35 wt% of dried weight of the biomass. Hydrogenolytic depolymerization of lignin is attracting increasing attention because of its capacity of utilizing lignin in its uncondensed form and compatibility with the biomass fractionation processes. Lignin is a natural aromatic polymer composed of a variety of monolignols associated with a series of lignin linkage motifs. Hydrogenolysis cleaves various ether bonds in lignin and releases phenolic monomers which can be further upgraded into valuable products, i.e., drugs, terephthalic acid, phenol. This review provides an overview of the state-of-the-art advances of the reagent (lignin), products (hydrol lignin), mass balance, and mechanism of the lignin hydrogenolysis reaction. The chemical structure of lignin is reviewed associated with the free radical coupling of monolignols and the chemical reactions of lignin upon isolation processes. The reactions of lignin linkages upon hydrogenolysis are discussed. The components of hydrol lignin and the selectivity production of phenolic monomers are reviewed. Future challenges on hydrogenolysis of lignin are proposed. This article provides an overview of lignin hydrogenolysis reaction which shows light on the generation of optimized lignin ready for hydrogenolytic depolymerization.

The potential of nanofibrillated cellulose from Hevea brasiliensis to produce films for bio-based packaging

Cellulose micro/nanofibril (MNFC) films are an interesting alternative to plastic-based films for application in biodegradable packaging. In this study, we aimed to produce and characterize MNFC films obtained from alkaline-pretreated rubberwood (Hevea brasiliensis) waste and Eucalyptus sp. commercial pulp. MNFC and films were evaluated regarding microstructure; crystallinity; stability; and physical, optical, mechanical, and barrier properties. A combined quality index (QI) was also calculated. Eucalyptus MNFC suspensions were more stable than H. brasiliensis. Both films had a hydrophobic surface (>90°) and high grease resistance (oil kit 12). H. brasiliensis films had lower transparency (26.4 %) and high crystallinity (∼89 %), while Eucalyptus films had lower permeability and higher mechanical strength. The QI of MNFC was 51 ± 5 for H. brasiliensis and 55 ± 4 for Eucalyptus, showing that both types of raw material have potential for application in the packaging industry and in the reinforcement of composites, as well as for high value-added applications in products made from special materials.

Second-generation biorefineries: single platform for the conversion of lignocellulosic wastes to environmentally important biofuels

The continuously increasing demands for various fossil fuels to achieve the day-to-day needs of the human population are growing and causing adverse effects on the environment and leading to the depletion of their natural resources. To overcome such drastic problems and minimize the production of greenhouse gases, lignocellulose biomass, which is an abundant and bio-renewable source present on earth with excellent properties and composition, has been used for decades to develop biofuels that can easily take over the place of conventional fuels. Lignocellulose biomass comprises polymeric sugars, i.e., cellulose and hemicellulose, and aromatic polymer, lignin, which are responsible for producing various bio-based products. However, utilizing lignocellulosic wastes for such purposes is needed but their recalcitrant structure makes it difficult to achieve their full usage. For this, several pretreatment approaches are developed to loosen the complexity between sugars and lignin. In some way, few of the conventional pretreatment methods are expensive, non-eco-friendly, and produce undesired by-products, causing a lower yield and reusability of enzymes used in the reaction. Utilizing novel pretreatment strategies that are cost-effective, help in increasing the yield of products, and are environment-friendly is required. Thus, incorporating nanoparticles and nanomaterials in the development of pretreatment and other strategies for the production of bio-based products is currently thriving. This review is designed in such a way that the readers can easily get brief knowledge about the production of important biofuels developed within second-generation biorefineries using lignocellulosic biomass. It also summarizes the importance of nanotechnology in different steps of biofuel development.

Polymeric phenylpropanoid derivatives crosslinked by hydroxyl fatty acids form the core structure of rape sporopollenin

Sporopollenin, a critical innovation in the evolution of terrestrial plants, is the core building brick for the outer wall of land-plant spores and pollen. Despite its significance, the basic structure of sporopollenin remains elusive due to its extreme chemical inertness. In this study, we used ethanolamine to completely dissolve rape sporopollenin and successfully identified a total of 22 components, including fatty acids, p-coumaric acid, sterols and polymeric phenylpropanoid derivatives. After that, using NaOH treatment and partial dissolution, alongside Arabidopsis mutants analysis and spectroscopic methods, we determined that polymeric phenylpropanoid derivatives crosslinked by hydroxyl fatty acids serve as the core structure of sporopollenin. The free hydroxyl groups and carboxyl groups of the polymeric phenylpropanoid derivatives can be modified by other fatty acids (C16:0, C18:0 and C18:3) as well as alcohols/phenols (for example, naringenin, β-sitosterol), resulting in a structure that protects pollen from terrestrial stresses. This discovery provides a basis for further exploration of sporopollenin's role in plant reproduction and evolution.