Lignin and biomass: a negative correlation for wood formation and lignin content in trees

From grass to gas and beyond: Anaerobic digestion as a key enabling technology for a residual grass biorefinery

Roadside grass clippings hold potential as a sustainable source of bioenergy as they do not compete with crops for land use, and are only partially utilized for low-value applications. In this study, we proposed using roadside grass as a sole feedstock for anaerobic digestion (AD) in three different settings, and assessed the potential of producing biomaterials and fertilizers from grass-based digestate. Wet continuous digestion at pilot scale and dry batch digestion at pilot and large scales resulted in biogas yields up to 700 Nm3.t-1 DOM with a methane content of 49-55 %. Despite promising results, wet AD had operational problems such as clogging and poor mixing; once upscaled, the dry digestion initially also presented an operational problem with acidification, which was overcome by the second trial. Digested grass fibers from the pilot dry AD were processed into biomaterials and performed similarly or better than the undigested fibers, while around 20 % performance reduction was observed when compared to reference wood fibers. A mass balance indicated reduced fiber recovery when higher biogas production was obtained. The liquid fraction from the pilot dry AD was characterized for its nutrient content and used as a biofertilizer in another study. In contrast, the leachate collected from the large-scale dry AD had a low nitrogen content and high chloride content that could hinder its further use. Finally, a regional market analysis was conducted showing that the biocomposites produced with the available grass fibers could substitute at least half of the current European market based on our results.

Adaptation mechanism of three Impatiens species to different habitats based on stem morphology, lignin and MYB4 gene

BACKGROUND

Impatiens is an important genus with rich species of garden plants, and its distribution is extremely extensive, which is reflected in its diverse ecological environment. However, the specific mechanisms of Impatiens' adaptation to various environments and the mechanism related to lignin remain unclear.

RESULTS

Three representative Impatiens species,Impatiens chlorosepala (wet, low degree of lignification), Impatiens uliginosa (aquatic, moderate degree of lignification) and Impatiens rubrostriata (terrestrial, high degree of lignification), were selected and analyzed for their anatomical structures, lignin content and composition, and lignin-related gene expression. There are significant differences in anatomical parameters among the stems of three Impatiens species, and the anatomical structure is consistent with the determination results of lignin content. Furthermore, the thickness of the xylem and cell walls, as well as the ratio of cell wall thickness to stem diameter have a strong correlation with lignin content. The anatomical structure and degree of lignification in Impatiens can be attributed to the plant's growth environment, morphology, and growth rate. Our analysis of lignin-related genes revealed a negative correlation between the MYB4 gene and lignin content. The MYB4 gene may control the lignin synthesis in Impatiens by controlling the structural genes involved in the lignin synthesis pathway, such as HCT, C3H, and COMT. Nonetheless, the regulation pathway differs between species of Impatiens.

CONCLUSIONS

This study demonstrated consistency between the stem anatomy of Impatiens and the results obtained from lignin content and composition analyses. It is speculated that MYB4 negatively regulates the lignin synthesis in the stems of three Impatiens species by regulating the expression of structural genes, and its regulation mechanism appears to vary across different Impatiens species. This study analyses the variations among different Impatiens plants in diverse habitats, and can guide further molecular investigations of lignin biosynthesis in Impatiens.

Exogenous methylglyoxal alleviates drought-induced 'plant diabetes' and leaf senescence in maize

Drought-induced leaf senescence is associated with high sugar levels, which bears some resemblance to the syndrome of diabetes in humans; however, the underlying mechanisms of such 'plant diabetes' on carbon imbalance and the corresponding detoxification strategy are not well understood. Here, we investigated the regulatory mechanism of exogenous methylglyoxal (MG) on 'plant diabetes' in maize plants under drought stress applied via foliar spraying during the grain-filling stage. Exogenous MG delayed leaf senescence and promoted photoassimilation, thereby reducing the yield loss induced by drought by 14%. Transcriptome and metabolite analyses revealed that drought increased sugar accumulation in leaves through inhibition of sugar transporters that facilitate phloem loading. This led to disequilibrium of glycolysis and overaccumulation of endogenous MG. Application of exogenous MG up-regulated glycolytic flux and the glyoxalase system that catabolyses endogenous MG and glycation end-products, ultimately alleviating 'plant diabetes'. In addition, the expression of genes facilitating anabolism and catabolism of trehalose-6-phosphate was promoted and suppressed by drought, respectively, and exogenous MG reversed this effect, implying that trehalose-6-phosphate signaling in the mediation of 'plant diabetes'. Furthermore, exogenous MG activated the phenylpropanoid biosynthetic pathway, promoting the production of lignin and phenolic compounds, which are associated with drought tolerance. Overall, our findings indicate that exogenous MG activates defense-related pathways to alleviate the toxicity derived from 'plant diabetes', thereby helping to maintain leaf function and yield production under drought.

Three-dimensional printing of wood

Natural wood has served as a foundational material for buildings, furniture, and architectural structures for millennia, typically shaped through subtractive manufacturing techniques. However, this process often generates substantial wood waste, leading to material inefficiency and increased production costs. A potential opportunity arises if complex wood structures can be created through additive processes. Here, we demonstrate an additive-free, water-based ink made of lignin and cellulose, the primary building blocks of natural wood, that can be used to three-dimensional (3D) print architecturally designed wood structures via direct ink writing. The resulting printed structures, after heat treatment, closely resemble the visual, textural, olfactory, and macro-anisotropic properties, including mechanical properties, of natural wood. Our results pave the way for 3D-printed wooden construction with a sustainable pathway to upcycle/recycle natural wood.

Biomass-derived multifunctional nanoscale carbon fibers toward fire warning sensors, supercapacitors and moist-electric generators

Nowadays, great effort has been devoted to designing biomass-derived nanoscale carbon fibers with controllable fibrous morphology, high conductivity, big specific surface area and multifunctional characteristics. Herein, a green and renewable strategy is performed to prepare the biomass-based nanoscale carbon fibers for fire warning sensor, supercapacitor and moist-electric generator. This preparation strategy thoroughly gets over the dependence of petroleum-based polymeride, and effectually improves the energy storage capacity, sensing sensitivity, humidity power generation efficiency of the obtaining biomass-based carbon nanofibers. Without the introduction of any active components or pseudocapacitive materials, the specific capacitance and energy density for biomass-based nanoscale carbon fibers achieve 143.58 F/g and 19.9 Wh/kg, severally. The biomass-based fire sensor displays excellent fire resistance, stability, and flame sensitivity with a response time of 2 s. Furthermore, the biomass-based moist-electric generator shows high power generation efficiency. The output voltage and current of five series connected and parallel-connected biomass-based moist-electric generators reaches 4.30 V and 43 μA, respectively. Notably, as the number of biomass-based moist-electric generators in series or parallel increases, the overall output voltage and current of the device system have a linear relationship. This work proposes a self-powered fire prediction system based on nanoscale carbon fibers that integrates sensing, power generation, and energy storage functions.

Comprehensive Time-Course Transcriptome Reveals the Crucial Biological Pathways Involved in the Seasonal Branch Growth in Siberian Elm (Ulmus pumila)

Timber, the most prevalent organic material on this planet, is the result of a secondary xylem emerging from vascular cambium. Yet, the intricate processes governing its seasonal generation are largely a mystery. To better understand the cyclic growth of vascular tissues in elm, we undertook an extensive study examining the anatomy, physiology, and genetic expressions in Ulmus pumila. We chose three robust 15-year-old elm trees for our study. The cultivars used in this study were collected from the Inner Mongolia Autonomous Region in China and nurtured in the tree farm of Shandong Normal University. Monthly samples of 2-year-old elm branches were taken from the tree from February to September. Marked seasonal shifts in elm branch vascular tissues were observed by phenotypic observation: In February, the cambium of the branch emerged from dormancy, spurring growth. By May, elms began generating secondary xylem, or latewood, recognized by its tiny pores and dense cell structure. From June to August, there was a marked increase in the thickness of the secondary xylem. Transcriptome sequencing provides a potential molecular mechanism for the thickening of elm branches and their response to stress. In February, the tree enhanced its genetic responses to cold and drought stress. The amplified expression of CDKB, CYCB, WOX4, and ARF5 in the months of February and March reinforced their essential role in the development of the vascular cambium in elm. Starting in May, the elm deployed carbohydrates as a carbon resource to synthesize the abundant cellulose and lignin necessary for the formation of the secondary wall. Major genes participating in cellulose (SUC and CESA homologs), xylan (UGD, UXS, IRX9, IRX10, and IRX14), and lignin (PAL, C4H, 4CL, HCT, C3H, COMT, and CAD) biosynthetic pathways for secondary wall formation were up-regulated by May or/and June. In conclusion, our findings provided a foundation for an in-depth exploration of the molecular processes dictating the seasonal growth of elm timber.

Histology, physiology, and transcriptomic and metabolomic profiling reveal the developmental dynamics of annual shoots in tree peonies (Paeonia suffruticosa Andr.)

The development of tree peony annual shoots is characterized by "withering", which is related to whether there are bud points in the leaf axillaries of annual shoots. However, the mechanism of "withering" in tree peony is still unclear. In this study, Paeonia ostii 'Fengdan' and P. suffruticosa 'Luoyanghong' were used to investigate dynamic changes of annual shoots through anatomy, physiology, transcriptome, and metabolome. The results demonstrated that the developmental dynamics of annual shoots of the two cultivars were comparable. The withering degree of P. suffruticosa 'Luoyanghong' was higher than that of P. ostii 'Fengdan', and their upper internodes of annual flowering shoots had a lower degree of lignin deposition, cellulose, C/N ratio, showing no obvious sclerenchyma, than the bottom ones and the whole internodes of vegetative shoot, which resulted in the "withering" of upper internodes. A total of 36 phytohormone metabolites were detected, of which 33 and 31 were detected in P. ostii 'Fengdan' and P. suffruticosa 'Luoyanghong', respectively. In addition, 302 and 240 differentially expressed genes related to lignin biosynthesis, carbon and nitrogen metabolism, plant hormone signal transduction, and zeatin biosynthesis were screened from the two cultivars. Furtherly, 36 structural genes and 40 transcription factors associated with the development of annual shoots were highly co-expressed, and eight hub genes involved in this developmental process were identified. Consequently, this study explained the developmental dynamic on the varied annual shoots through multi-omics, providing a theoretical foundation for germplasm innovation and the mechanized harvesting of tree peony annual shoots.

Engineering traits through CRISPR/cas genome editing in woody species to improve forest diversity and yield

Dangers confronting forest ecosystems are many and the strength of these biological systems is deteriorating, thus substantially affecting tree physiology, phenology, and growth. The establishment of genetically engineered trees into degraded woodlands, which would be adaptive to changing climate, could help in subsiding ecological threats and bring new prospects. This should not be resisted due to the apprehension of transgene dispersal in forests. Consequently, it is important to have a deep insight into the genetic structure and phenotypic limits of the reproductive capability of tree stands/population(s) to endure tolerance and survival. Importantly, for a better understanding of genes and their functional mechanisms, gene editing (GeEd) technology is an excellent molecular tool to unravel adaptation progressions. Therefore, GeEd could be harnessed for resolving the allelic interactions for the creation of gene diversity, and transgene dispersal may be alleviated among the population or species in different bioclimatic zones around the globe. This review highlights the potential of the CRISPR/Cas tools in genomic, transcriptomic, and epigenomic-based assorted and programmable alterations of genes in trees that might be able to fix the trait-specific gene function. Also, we have discussed the application of diverse forms of GeEd to genetically improve several traits, such as wood density, phytochemical constituents, biotic and abiotic stress tolerance, and photosynthetic efficiency in trees. We believe that the technology encourages fundamental research in the forestry sector besides addressing key aspects, which might fasten tree breeding and germplasm improvement programs worldwide.

Brassinosteroids affect wood development and properties of Fraxinus mandshurica

Introduction

Xylem development plays a crucial role in wood formation in woody plants. In recent years, there has been growing attention towards the impact of brassinosteroids (BRs) on this xylem development. In the present study, we evaluated the dynamic variation of xylem development in Fraxinus mandshurica (female parent, M8) and a novel interspecific hybrid F. mandshurica × Fraxinus sogdiana (1601) from May to August 2020.

Methods

We obtained RNA-Seq transcriptomes of three tissue types (xylem, phloem, and leaf) to identify the differences in xylem-differentially expressed genes (X-DEGs) and xylem-specifically expressed genes (X-SEGs) in M8 and 1601 variants. We then further evaluated these genes via weighted gene co-expression network analysis (WGCNA) alongside overexpressing FmCPD, a BR biosynthesis enzyme gene, in transient transgenic F. mandshurica.

Results

Our results indicated that the xylem development cycle of 1601 was extended by 2 weeks compared to that of M8. In addition, during the later wood development stages (secondary wall thickening) of 1601, an increased cellulose content (14%) and a reduced lignin content (11%) was observed. Furthermore, vessel length and width increased by 67% and 37%, respectively, in 1601 compared with those of M8. A total of 4589 X-DEGs were identified, including enzymes related to phenylpropane metabolism, galactose metabolism, BR synthesis, and signal transduction pathways. WGCNA identified hub X-SEGs involved in cellulose synthesis and BR signaling in the 1601 wood formation-related module (CESA8, COR1, C3H14, and C3H15); in contrast, genes involved in phenylpropane metabolism were significantly enriched in the M8 wood formation-related module (CCoAOMT and CCR). Moreover, overexpression of FmCPD in transient transgenic F. mandshurica affected the expression of genes associated with lignin and cellulose biosynthesis signal transduction. Finally, BR content was determined to be approximately 20% lower in the M8 xylem than in the 1601 xylem, and the exogenous application of BRs (24-epi brassinolide) significantly increased the number of xylem cell layers and altered the composition of the secondary cell walls in F. mandshurica.

Discussion

Our findings suggest that BR biosynthesis and signaling play a critical role in the differing wood development and properties observed between M8 and 1601 F. mandshurica.

Effect of Light of Different Spectral Compositions on Pro/Antioxidant Status, Content of Some Pigments and Secondary Metabolites and Expression of Related Genes in Scots Pine

The aim of this study was to investigate the effect of light quality (white fluorescent light, WFL, containing UV components), red light (RL, 660 nm), blue light (BL, 450 nm), and white LED light (WL, 450 + 580 nm) on the components of the cellular antioxidant system in Pinus sylvestris L. in needles, roots, and hypocotyls, focusing on the accumulation of key secondary metabolites and the expression of related genes. The qualitative and quantitative composition of carotenoids; the content of the main photosynthetic pigments, phenolic compounds, flavonoids (catechins, proanthocyanidins, anthocyanins), ascorbate, and glutathione; the activity of the main antioxidant enzymes; the content of hydrogen peroxide; and the intensity of lipid peroxidation (MDA and 4-HNE contents) were determined. RL resulted in an increase in the content of hydrogen peroxide and 4-HNE, as well as the total fraction of flavonoids in the needles. It also enhanced the expression of several PR (pathogen-related) genes compared to BL and WL. WFL increased the content of phenols, including flavonoids, and enhanced the overall activity of low-molecular antioxidants in needles and hypocotyls. BL increased the content of ascorbate and glutathione, including reduced glutathione, in the needles and simultaneously decreased the activity of peroxidases. Thus, by modifying the light quality, it is possible to regulate the accumulation of secondary metabolites in pine roots and needles, thereby influencing their resistance to various biotic and abiotic stressors.

Algal-based wood as a green and sustainable alternative for environmentally friendly & flexible electronic devices membrane bioreactor

Electronic are usually constructed from non-renewable, non-biodegradable, and hazardous materials. Due to the frequent upgrading or discarding of electronic devices, which contributes significantly to environmental pollution, there is a high demand for electronics made from renewable and biodegradable materials with less harmful components. To this end, due to their flexibility, strong mechanical, and optical properties, wood-based electronics have become very appealing as substrates especially for flexible electronics and optoelectronics. However, incorporating numerous features including high conductivity and transparency, flexibility, and mechanical robustness into an environmentally friendly electronic device remains very challenging. Herein, authors have provided the techniques used to fabricate sustainable wood based flexible electronics coupled with their chemical, mechanical, optical, thermal, thermomechanical, and surface properties for various applications. Additionally, the synthesis of a conductive ink based on lignin and the development of translucent wood as a substrate are covered. Future developments and broader applications of wood-based flexible materials are discussed in the final section of the study, with an emphasis on their potential in fields including wearable electronics, renewable energy, and biomedical devices. This research improves upon prior efforts by demonstrating new ways to simultaneously attain better mechanical and optical qualities and environmental sustainability.

Moderate Salinity Stress Increases the Seedling Biomass in Oilseed Rape (Brassica napus L.)

Oilseed rape (Brassica napus L.), an important oil crop of the world, suffers various abiotic stresses including salinity stress during the growth stage. While most of the previous studies paid attention to the adverse effects of high salinity stress on plant growth and development, as well as their underlying physiological and molecular mechanisms, less attention was paid to the effects of moderate or low salinity stress. In this study, we first tested the effects of different concentrations of NaCl solution on the seedling growth performance of two oilseed rape varieties (CH336, a semi-winter type, and Bruttor, a spring type) in pot cultures. We found that moderate salt concentrations (25 and 50 mmol L^-1 NaCl) can stimulate seedling growth by a significant increase (10~20%, compared to controls) in both above- and underground biomasses, as estimated at the early flowering stage. We then performed RNA-seq analyses of shoot apical meristems (SAMs) from six-leaf-aged seedlings under control (CK), low (LS, 25 mmol L^-1), and high (HS, 180 mmol L^-1) salinity treatments in the two varieties. The GO and KEGG enrichment analyses of differentially expressed genes (DEGs) demonstrated that such a stimulating effect on seedling growth by low salinity stress may be caused by a more efficient capacity for photosynthesis as compensation, accompanied by a reduced energy loss for the biosynthesis of secondary metabolites and redirecting of energy to biomass formation. Our study provides a new perspective on the cultivation of oilseed rape in saline regions and new insights into the molecular mechanisms of salt tolerance in Brassica crops. The candidate genes identified in this study can serve as targets for molecular breeding selection and genetic engineering toward enhancing salt tolerance in B. napus.

Recent advancements in lignocellulose biomass-based carbon fiber: Synthesis, properties, and applications

A growing need to reduce the global carbon footprint has prompted all sectors to make significant efforts in this direction. For example, there has been much focus on green carbon fiber sustainability. For example, it was found that the polyaromatic heteropolymer lignin might act as an intermediary in synthesising carbon fiber. Biomass is seen as a potential carbon accommodated solid natural sources that protects the nature and has a big overall supply and widespread distribution. With growing environmental concern in recent years, biomass has gained appeal as a raw material for production of carbon fibers. Especially, the positives of lignin material include its reasonable budget, sustainability, and higher carbon content, which makes it a dominating precursor. This review has examined a variety of bio precursors that help produce lignin and have higher lignin concentrations. In addition, there has been much research on plant sources, lignin types, factors affecting carbon fiber synthesis, spinning methods, stabilization, carbonization, and activation the characterisation techniques used for the lignin carbon fiber to comprehend the structure and features. In addition, an overview of the applications that use lignin carbon fiber has been provided.

Biobased Transesterification Vitrimers

The rapid increase in the use of plastics and the related sustainability issues, including the depletion of global petroleum reserves, have rightly sparked interest in the use of biobased polymer feedstocks. Thermosets cannot be remolded, processed, or recycled, and hence cannot be reused because of their permanent molecular architecture. Vitrimers have emerged as a novel polymer family capable of bridging the difference between thermoplastic and thermosets. Vitrimers enable unique recycling strategies, however, it is still important to understand where the raw material feedstocks originate from. Transesterification vitrimers derived from renewable resources are a massive opportunity, however, limited research has been conducted in this specific family of vitrimers. This review article provides a comprehensive overview of transesterification vitrimers produced from biobased monomers. The focus is on the biomass structural suitability with dynamic covalent chemistry, as well as the viability of the synthetic methods.

Biochemical Aspects of the Spiral Grain Formation in Scots Pine (Pinus Sylvestris L.) Wood. Some Differences and Similarities with Biochemical Indicators of Abnormal Xylogenesis in Karelian Birch (Betula Pendula Roth Var. Carelica (Mercl.) Hämet-Ahti)

BACKGROUND

AOS enzymes can be biochemical indicators of abnormal xylogenesis in Scots pine, and this mechanism has similar features with the metabolic base of abnormal xylogenesis in Karelian birch.

OBJECTIVE

AOS enzymes' activity in 150-300-year-old Pinus sylvestris L. wood with straight-- grained wood and right-twisted spiral-grained wood, expressed in varying degrees (5-20 angle), grew in three sample plots in lingonberry and blueberry pine forest stands of different ages (100-300 years) in the middle taiga subzone in the Republic of Karelia.

METHODS

Plant tissues were ground in liquid nitrogen in a uniform mass and homogenized at 4°C in the buffer containing 50 mM HEPES (pH 7.5), 1 mM EDTA, 1 mM EGTA, 3 mM DTT, 5 mM MgCl2 and 0.5 mM PMSF. After 20 min extraction, the homogenate was centrifuged at 10000 g for 20 min (MPW-351R, Poland). The sediment was washed in the buffer thrice. The pooled supernatant and sediment were dialyzed at 4°C for 18-20 h against a tenfold diluted homogenization buffer. The enzymes' activity was determined spectrophotometrically (Spectrophotometer SF-2000, OKB Spectr, Russia). Proteins in the extracts were quantified by the method of Bradford.

RESULTS

The study showed that the activity of SS, ApInv, CAT, POD and PPO in xylem and PPO in phloem were biochemical indicators for abnormal wood of P. sylvestris. We noticed an increase in sucrose metabolism in the apoplast and the activity of POD and PPO under spiral-grain wood formation like under figured wood formation earlier. We assume that the alternative pathway of sucrose metabolism (an indicator of abnormal xylogenesis in B. pendula var. carelica plants) that lead to restructuring of AOS enzymes have the same biochemical regularities in the spiral-grain wood formation in P. sylvestris.

CONCLUSION

The study showed that the differences in the AOS enzyme's activity in P. sylvestris during the formation of straight-grained and spiral-grained wood were revealed for the first time. The increased CAT, POD and PPO activities in xylem with a decrease in SS and an increase in Ap- Inv during spiral-grained wood formation can be biochemical markers of these structural anomalies. Metabolic regularities found in the AOS enzyme complex during spiral-grained wood formation do not contradict those found earlier during figured wood formation in B. pendula var. carelica. The identified patterns can form the base for diagnostics of P. sylvestris wood quality in forest seed plantations and in their natural growth, which is necessary both for fundamental science and in various industry areas while high-quality material harvesting.

Biomechanical traits of salt marsh vegetation are insensitive to future climate scenarios

Salt marshes provide wave and flow attenuation, making them attractive for coastal protection. It is necessary to predict their coastal protection capacity in the future, when climate change will increase hydrodynamic forcing and environmental parameters such as water temperature and CO₂ content. We exposed the European salt marsh species Spartina anglica and Elymus athericus to enhanced water temperature (+ 3°) and CO₂ (800 ppm) levels in a mesocosm experiment for 13 weeks in a full factorial design. Afterwards, the effect on biomechanic vegetation traits was assessed. These traits affect the interaction of vegetation with hydrodynamic forcing, forming the basis for wave and flow attenuation. Elymus athericus did not respond to any of the treatments suggesting that it is insensitive to such future climate changes. Spartina anglica showed an increase in diameter and flexural rigidity, while Young's bending modulus and breaking force did not differ between treatments. Despite some differences between the future climate scenario and present conditions, all values lie within the natural trait ranges for the two species. Consequently, this mesocosm study suggests that the capacity of salt marshes to provide coastal protection is likely to remain constantly high and will only be affected by future changes in hydrodynamic forcing.

Proteomic Analysis of Barley (Hordeum vulgare L.) Leaves in Response to Date Palm Waste Compost Application

Composts are an emerging biofertilizers used in agronomy that can improve crop performance, but much less is known regarding their modes of action. The current study aimed to investigate the differentially abundant proteins (DAPs) in barley leaves associated with growth promotion induced by application of date palm waste compost. Morphophysiological measurements revealed that compost induced a significant increase in plant height, chlorophyll content, gas exchange parameters and plant biomass. LC-MS/MS analyses indicate that compost induced global changes in the proteome of barley leaves. A total of 62 DAPs (26 upregulated and 36 downregulated) among a total of 2233 proteins were identified in response to compost application. The expression of DAPs was further validated based on qRT-PCR. Compost application showed altered abundance of several proteins related to abiotic stress, plant defense, redox homeostasis, transport, tricarboxylic acid cycle, carbohydrate, amino acid, energy and protein metabolism. Furthermore, proteins related to metabolic processes of phytohormone, DNA methylation and secondary metabolites were induced. These results indicate that barley responds to compost application by complex metabolism pathways and may result in a positive alteration in a physiological and metabolic barley plant state which consequently could lead to improved growth and stress adaptation observed in compost-treated plants.

Molecular structural dataset of lignin macromolecule elucidating experimental structural compositions

Lignin is one of the most abundant biopolymers in nature and has great potential to be transformed into high-value chemicals. However, the limited availability of molecular structure data hinders its potential industrial applications. Herein, we present the Lignin Structural (LGS) Dataset that includes the molecular structure of milled wood lignin focusing on two major monomeric units (coniferyl and syringyl), and the six most common interunit linkages (phenylpropane β-aryl ether, resinol, phenylcoumaran, biphenyl, dibenzodioxocin, and diaryl ether). The dataset constitutes a unique resource that covers a part of lignin’s chemical space characterized by polymer chains with lengths in the range of 3 to 25 monomer units. Structural data were generated using a sequence-controlled polymer generation approach that was calibrated to match experimental lignin properties. The LGS dataset includes 60 K newly generated lignin structures that match with high accuracy (~90%) the experimentally determined structural compositions available in the literature. The LGS dataset is a valuable resource to advance lignin chemistry research, including computational simulation approaches and predictive modelling.

Measurement(s)	molecular structure
Technology Type(s)	Computer Modeling
Factor Type(s)	monomer ratio • bond frequency • degree of polymerization
Sample Characteristic - Organism	coniferous (softwood) • deciduous (hardwood)

Bias-free solar hydrogen production at 19.8 mA cm-2 using perovskite photocathode and lignocellulosic biomass

Solar hydrogen production is one of the ultimate technologies needed to realize a carbon-neutral, sustainable society. However, an energy-intensive water oxidation half-reaction together with the poor performance of conventional inorganic photocatalysts have been big hurdles for practical solar hydrogen production. Here we present a photoelectrochemical cell with a record high photocurrent density of 19.8 mA cm^-2 for hydrogen production by utilizing a high-performance organic-inorganic halide perovskite as a panchromatic absorber and lignocellulosic biomass as an alternative source of electrons working at lower potentials. In addition, value-added chemicals such as vanillin and acetovanillone are produced via the selective depolymerization of lignin in lignocellulosic biomass while cellulose remains close to intact for further utilization. This study paves the way to improve solar hydrogen productivity and simultaneously realize the effective use of lignocellulosic biomass.

An insight into the principles of lignocellulosic biomass-based zero-waste biorefineries: a green leap towards imperishable energy-based future

Lignocellulosic biomass (LCB) is an energy source that has a huge impact in today's world. The depletion of fossil fuels, increased pollution, climatic changes, etc. have led the public and private sectors to move towards sustainability i.e. using LCB for the production of biofuels and value-added compounds. A major bottleneck of the process is the recalcitrant nature of LCB. This can be overcome by using various pretreatment strategies like physical, chemical, biological, physicochemical, etc. Further, the pretreated biomass is made to undergo various steps like hydrolysis, saccharification, etc. for the conversion of value-added products and the remaining waste residues can be further utilized for the synthesis of secondary products thus favouring the zero-waste biorefinery concept. Currently, microorganisms are being explored for their use in biorefinery but the unavailability of commercial strains is a major limitation. Thus, the use of metagenomics can be used to overcome the limitation which is both cost-effective and environmentally friendly. The review deliberates the composition of LCBs, and their recalcitrance nature, followed by the structural changes caused by various pretreatment methods. The further steps in biorefineries, strategies for the development of zero-waste refineries, bottlenecks, and suggestions are also discussed. Special emphasis is given to the use of metagenomics for the discovery of microorganisms efficient for zero-waste biorefineries.

Building a risk matrix for the safety assessment of wood derived biochars

Biochar is recognized as an efficient amendment and soil improver. However, environmental and quality assessments are needed to ensure the sustainability of its use in agriculture. This work considers the biochar's chemical-physical characterization and its potential phyto- and geno-toxicity, assessed with germination and Ames tests, obtaining valuable information for a safe field application. Three biochar types, obtained from gasification at different temperatures of green biomasses from the Tuscan-Emilian Apennines (in Italy), were compared through a broad chemical, physical and biological evaluation. The results obtained showed the relevance of temperature in determining the chemical and morphological properties of biochar, which was shown with several analytical techniques such as the elemental composition, water holding capacity, ash content, but also with FTIR and X-ray spectroscopies. These techniques showed the presence of different relevant surface aliphatic and aromatic groups. The procedures for evaluating the potential toxicity using seeds germination and Ames genotoxicity assay highlights that biochar does not cause detrimental effects when it enters in contact with soil, micro- and macro-organisms, and plants. The genotoxicity test provided a new highlight in evaluating biochar environmental safety.

Acclimation and Compensating Metabolite Responses to UV-B Radiation in Natural and Transgenic Populus spp. Defective in Lignin Biosynthesis

Plants have evolved to protect leaf mesophyll tissue from damage caused by UV-B radiation by producing an array of UV-absorbing secondary metabolites. Flavonoids (phenolic glycosides) and sinapate esters (hydroxycinnamates) have been implicated as UV-B protective compounds because of the accumulation in the leaf epidermis and the strong absorption in the wavelengths corresponding to UV. Environmental adaptations by plants also generate a suite of responses for protection against damage caused by UV-B radiation, with plants from high elevations or low latitudes generally displaying greater adaptation or tolerance to UV-B radiation. In an effort to explore the relationships between plant lignin levels and composition, the origin of growth elevation, and the hierarchical synthesis of UV-screening compounds, a collection of natural variants as well as transgenic Populus spp. were examined for sensitivity or acclimation to UV-B radiation under greenhouse and laboratory conditions. Noninvasive, ecophysiological measurements using epidermal transmittance and chlorophyll fluorescence as well as metabolite measurements using UPLC-MS generally revealed that the synthesis of anthocyanins, flavonoids, and lignin precursors are increased in Populus upon moderate to high UV-B treatment. However, poplar plants with genetic modifications that affect lignin biosynthesis, or natural variants with altered lignin levels and compositions, displayed complex changes in phenylpropanoid metabolites. A balance between elevated metabolic precursors to protective phenylpropanoids and increased biosynthesis of these anthocyanins, flavonoids, and lignin is proposed to play a role in the acclimation of Populus to UV-B radiation and may provide a useful tool in engineering plants as improved bioenergy feedstocks.

Laser Processing of Flexible In-Plane Micro-supercapacitors: Progresses in Advanced Manufacturing of Nanostructured Electrodes

Flexible in-plane architecture micro-supercapacitors (MSCs) are competitive candidates for on-chip miniature energy storage applications owing to their light weight, small size, high flexibility, as well as the advantages of short charging time, high power density, and long cycle life. However, tedious and time-consuming processes are required for the manufacturing of high-resolution interdigital electrodes using conventional approaches. In contrast, the laser processing technique enables high-efficiency high-precision patterning and advanced manufacturing of nanostructured electrodes. In this review, the recent advances in laser manufacturing and patterning of nanostructured electrodes for applications in flexible in-plane MSCs are comprehensively summarized. Various laser processing techniques for the synthesis, modification, and processing of interdigital electrode materials, including laser pyrolysis, reduction, oxidation, growth, activation, sintering, doping, and ablation, are discussed. In particular, some special features and merits of laser processing techniques are highlighted, including the impacts of laser types and parameters on manufacturing electrodes with desired morphologies/structures and their applications on the formation of high-quality nanoshaped graphene, the selective deposition of nanostructured materials, the controllable nanopore etching and heteroatom doping, and the efficient sintering of nanometal products. Finally, the current challenges and prospects associated with the laser processing of in-plane MSCs are also discussed. This review will provide a useful guidance for the advanced manufacturing of nanostructured electrodes in flexible in-plane energy storage devices and beyond.

Phylogenomics Resolves the Phylogeny of Theaceae by Using Low-Copy and Multi-Copy Nuclear Gene Makers and Uncovers a Fast Radiation Event Contributing to Tea Plants Diversity

Simple Summary

The Theaceae includes more than 300 species of great morphological diversity and has immense economic, cultural, and ornamental values. However, the evolutionary history of this family remains elusive. We integrated 91 genomes and transcriptome datasets of Theaceae and successfully resolved the phylogeny of Theaceae including relatives of cultivated tea plants from both extensive low-copy and multi-copy nuclear gene markers. Bayes-based molecular dating revealed that the ancestor of the tea family originated slightly earlier than the K-Pg boundary (Mass extinction events including the extinction of dinosaurs) with early diversification of three tribes associated with the Early Eocene Climatic Optimum. Further speciation analysis suggested a sole significant diversification shift rate in the common ancestor of Camellia associated with the Mid-Miocene Climatic Optimum. Collectively, polyploidy events, and key morphological innovation characters, such as pericarp with seed coat hardening, could possibly contribute to the Theaceae species diversity.

Abstract

Tea is one of the three most popular nonalcoholic beverages globally and has extremely high economic and cultural value. Currently, the classification, taxonomy, and evolutionary history of the tea family are largely elusive, including phylogeny, divergence, speciation, and diversity. For understanding the evolutionary history and dynamics of species diversity in Theaceae, a robust phylogenetic framework based on 1785 low-copy and 79,103 multi-copy nuclear genes from 91 tea plant genomes and transcriptome datasets had been reconstructed. Our results maximumly supported that the tribes Stewartieae and Gordonieae are successive sister groups to the tribe Theeae from both coalescent and super matrix ML tree analyses. Moreover, in the most evolved tribe, Theeae, the monophyletic genera Pyrenaria, Apterosperma, and Polyspora are the successive sister groups of Camellia. We also yield a well-resolved relationship of Camellia, which contains the vast majority of Theaceae species richness. Molecular dating suggests that Theaceae originated in the late L-Cretaceous, with subsequent early radiation under the Early Eocene Climatic Optimal (EECO) for the three tribes. A diversification rate shift was detected in the common ancestors of Camellia with subsequent acceleration in speciation rate under the climate optimum in the early Miocene. These results provide a phylogenetic framework and new insights into factors that likely have contributed to the survival of Theaceae, especially a successful radiation event of genus Camellia members to subtropic/tropic regions. These novel findings will facilitate the efficient conservation and utilization of germplasm resources for breeding cultivated tea and oil-tea. Collectively, these results provide a foundation for further morphological and functional evolutionary analyses across Theaceae.

Monolignol export by diffusion down a polymerization-induced concentration gradient

Lignin, the second most abundant biopolymer, is a promising renewable energy source and chemical feedstock. A key element of lignin biosynthesis is unknown: how do lignin precursors (monolignols) get from inside the cell out to the cell wall where they are polymerized? Modeling indicates that monolignols can passively diffuse through lipid bilayers, but this has not been tested experimentally. We demonstrate significant monolignol diffusion occurs when laccases, which consume monolignols, are present on one side of the membrane. We hypothesize that lignin polymerization could deplete monomers in the wall, creating a concentration gradient driving monolignol diffusion. We developed a two-photon microscopy approach to visualize lignifying Arabidopsis thaliana root cells. Laccase mutants with reduced ability to form lignin polymer in the wall accumulated monolignols inside cells. In contrast, active transport inhibitors did not decrease lignin in the wall and scant intracellular phenolics were observed. Synthetic liposomes were engineered to encapsulate laccases, and monolignols crossed these pure lipid bilayers to form polymer within. A sink-driven diffusion mechanism explains why it has been difficult to identify genes encoding monolignol transporters and why the export of varied phenylpropanoids occurs without specificity. It also highlights an important role for cell wall oxidative enzymes in monolignol export.

Evaluation of Cell Wall Chemistry of Della and Its Mutant Sweet Sorghum Stalks

The cell wall compositional (lignin and polysaccharides) variation of two sweet sorghum varieties, Della (D) and its variant REDforGREEN (RG), was evaluated at internodes (IN) and nodes (N) using high-performance liquid chromatography (HPLC), pyrolysis-gas chromatography-mass spectrometry (Py-GCMS), X-ray diffraction (XRD), and two-dimensional (2D) ¹H-¹³C nuclear magnetic resonance (NMR). The stalks were grown in 2018 (D1 and RG1) and 2019 (D2 and RG2) seasons. In RG1, Klason lignin reductions by 16-44 and 2-26% were detected in IN and N, respectively. The analyses also revealed that lignin from the sorghum stalks was enriched in guaiacyl units and the syringyl/guaiacyl ratio was increased in RG1 and RG2, respectively, by 96% and more than 2-fold at IN and 61 and 23% at N. The glucan content was reduced by 23-27% for RG1 and by 17-22% for RG2 at internodes. Structural variations due to changes in both cellulose- and hemicellulose-based sugars were detected. The nonacylated and γ-acylated β-O-4 linkages were the main interunit linkages detected in lignin. These results indicate compositional variation of stalks due to the RG variation, and the growing season could influence their mechanical and lodging behavior.

Plant interactions control the carbon distribution of Dodonaea viscosa in karst regions

Biomass and carbon (C) distribution are suggested as strategies of plant responses to resource stress. Understanding the distribution patterns of biomass and C is the key to vegetation restoration in fragile ecosystems, however, there is limited understanding of the intraspecific biomass and C distributions of shrubs resulting from plant interactions in karst areas. In this study, three vegetation restoration types, a Dodonaea viscosa monoculture (DM), a Eucalyptus maideni and D. viscosa mixed-species plantation (EDP) and a Pinus massoniana and D. viscosa mixed-species plantation (PDP), were selected to determine the effects of plant interactions on the variations in the C distributions of D. viscosa among the three vegetation restoration types following 7 years of restoration. The results showed that: (1) plant interactions decreased the leaf biomass fraction. The interaction of P. massoniana and D. viscosa decreased the branch biomass fraction and increased the stem and root biomass fraction, but not the interaction of E. maideni and D. viscosa. Plant interactions changed the C concentrations of stems and roots rather than those of leaves and branches. (2) Plant interactions affected the soil nutrients and forest characteristics significantly. Meanwhile, the biomass distribution was affected by soil total nitrogen, clumping index and gap fraction; the C concentrations were influenced by the leaf area index and soil total phosphorus. (3) The C storage proportions of all the components correlated significantly with the proportion of biomass. Our results suggested that both the biomass distribution and C concentration of D. viscosa were affected by plant interactions, however, the biomass fraction not the C concentration determines the C storage fraction characteristics for D. viscosa.

High throughput method development and optimised production of leaf protein concentrates with potential to support the agri-industry

Invasive plants offer an interesting and unconventional source of protein and the considerable investment made towards their eradication can potentially be salvaged through their revalorisation. To identify viable sources, effective and high-throughput screening methods are required, as well as efficient procedures to isolate these components. Rigorous assessment of low-cost, high-throughput screening assays for total sugar, phenolics and protein was performed, and ninhydrin, Lever and Fast Blue assays were found to be most suitable owing to high reliability scores and false positive errors less than 1%. These assays were used to characterise invasive Scottish plants such as Gorse (Ulex europeans), Broom (Cystisus scoparius) and Fireweed (Chamaenerion angustifolium). Protein extraction (alkali-, heat- and enzyme assisted) were tested on these plants, and further purification (acid and ethanol precipitation, as well as ultrafiltration) procedures were tested on Gorse, based on protein recovery values. Cellulase treatment and ethanol precipitation gave the highest protein recovery (64.0 ± 0.5%) and purity (96.8 ± 0.1%) with Gorse. The amino acid profile of the purified protein revealed high levels of essential amino acids (34.8 ± 0.0%). Comparison of results with preceding literature revealed a strong association between amino acid profiles and overall protein recovery with the extraction method employed. The final purity of the protein concentrates was closely associated to the protein content of the initial plant mass. Leaf protein extraction technology can effectively raise crop harvest indices, revalorise underutilised plants and waste streams.

Analysis of Phenotypic Characteristics and Sucrose Metabolism in the Roots of Raphanus sativus L

The taproot of radish (Raphanus sativus L.) is an important sink organ; it is morphologically diverse and contains large amounts of secondary metabolites. Sucrose metabolism is believed to be important in the development of sink organs. We measured the amounts of glucose, fructose, and sucrose in the roots of sixty three radish accessions and analyzed the association between the sugar content and the root phenotype. Fructose content correlated with the root color and length characteristics, glucose was the most abundant sugar in the roots, and the sucrose content was very low, compared to that of the hexoses in most of the accessions. Expression analysis of the genes involved in sucrose metabolism, transportation, starch synthesis, and cell wall synthesis was performed through RNA sequencing. The genes encoding sucrose synthases (SUSY) and the enzymes involved in the synthesis of cellulose were highly expressed, indicating that SUSY is involved in cell wall synthesis in radish roots. The positive correlation coefficient (R) between the sucrose content and the expression of cell wall invertase and sugar transporter proteins suggest that hexose accumulation could occur through the apoplastic pathway in radish roots. A positive R score was also obtained when comparing the expression of genes encoding SUSY and fructokinase (FK), suggesting that the fructose produced by SUSY is mostly phosphorylated by FK. In addition, we concluded that sucrose was the most metabolized sugar in radish roots.

Do different growth rates of trees cause distinct habitat qualities for saproxylic assemblages?

In production forests, a common silvicultural objective is enhancing tree growth rates. The growth rate influences both mechanical and biochemical properties of wood, which may have an impact on dead wood inhabiting (i.e. saproxylic) species. In this study, we tested for the first time whether tree growth rates affect dead-wood associated assemblages in general and the occurrence of red-listed species in particular. We sampled saproxylic beetles (eclector traps) and fungi (DNA metabarcoding of wood samples) in dead trunks of Norway spruce (Picea abies), which had different growth rates within the same hemiboreal forests in Sweden. A high proportion of fungi showed a positive association to increasing tree growth. This resulted in higher fungal richness in fast-grown trees both at the trunk scale and across multiple studied trunks. Such patterns were not observed for saproxylic beetles. However, a set of species (both beetles and fungi) preferred slow-grown wood. Moreover, the total number of red-listed species was highest in slow-grown trunks. We conclude that dead wood from slow-grown trees hosts relatively fewer saproxylic species, but a part of these may be vulnerable to production forestry. It implies that slow-grown trees should be a target in nature conservation. However, where slow-grown trees are absent, for instance in forests managed for a high biomass production, increasing the volumes of dead wood from fast-grown trees may support many species.

Enzyme Complexes of Ptr4CL and PtrHCT Modulate Co-enzyme A Ligation of Hydroxycinnamic Acids for Monolignol Biosynthesis in Populus trichocarpa

Co-enzyme A (CoA) ligation of hydroxycinnamic acids by 4-coumaric acid:CoA ligase (4CL) is a critical step in the biosynthesis of monolignols. Perturbation of 4CL activity significantly impacts the lignin content of diverse plant species. In Populus trichocarpa, two well-studied xylem-specific Ptr4CLs (Ptr4CL3 and Ptr4CL5) catalyze the CoA ligation of 4-coumaric acid to 4-coumaroyl-CoA and caffeic acid to caffeoyl-CoA. Subsequently, two 4-hydroxycinnamoyl-CoA:shikimic acid hydroxycinnamoyl transferases (PtrHCT1 and PtrHCT6) mediate the conversion of 4-coumaroyl-CoA to caffeoyl-CoA. Here, we show that the CoA ligation of 4-coumaric and caffeic acids is modulated by Ptr4CL/PtrHCT protein complexes. Downregulation of PtrHCTs reduced Ptr4CL activities in the stem-differentiating xylem (SDX) of transgenic P. trichocarpa. The Ptr4CL/PtrHCT interactions were then validated in vivo using biomolecular fluorescence complementation (BiFC) and protein pull-down assays in P. trichocarpa SDX extracts. Enzyme activity assays using recombinant proteins of Ptr4CL and PtrHCT showed elevated CoA ligation activity for Ptr4CL when supplemented with PtrHCT. Numerical analyses based on an evolutionary computation of the CoA ligation activity estimated the stoichiometry of the protein complex to consist of one Ptr4CL and two PtrHCTs, which was experimentally confirmed by chemical cross-linking using SDX plant protein extracts and recombinant proteins. Based on these results, we propose that Ptr4CL/PtrHCT complexes modulate the metabolic flux of CoA ligation for monolignol biosynthesis during wood formation in P. trichocarpa.

Uncovering miRNA-mRNA Regulatory Modules in Developing Xylem of Pinus massoniana via Small RNA and Degradome Sequencing

Xylem is required for the growth and development of higher plants to provide water and mineral elements. The thickening of the xylem secondary cell wall (SCW) not only improves plant survival, but also provides raw materials for industrial production. Numerous studies have found that transcription factors and non-coding RNAs regulate the process of SCW thickening. Pinus massoniana is an important woody tree species in China and is widely used to produce materials for construction, furniture, and packaging. However, the target genes of microRNAs (miRNAs) in the developing xylem of P. massoniana are not known. In this study, a total of 25 conserved miRNAs and 173 novel miRNAs were identified via small RNA sequencing, and 58 differentially expressed miRNAs were identified between the developing xylem (PM_X) and protoplasts isolated from the developing xylem (PM_XP); 26 of these miRNAs were significantly up-regulated in PM_XP compared with PM_X, and 32 were significantly down-regulated. A total of 153 target genes of 20 conserved miRNAs and 712 target genes of 113 novel miRNAs were verified by degradome sequencing. There may be conserved miRNA-mRNA modules (miRNA-MYB, miRNA-ARF, and miRNA-LAC) involved in softwood and hardwood formation. The results of qRT-PCR-based parallel validation were in relatively high agreement. This study explored the potential regulatory network of miRNAs in the developing xylem of P. massoniana and provides new insights into wood formation in coniferous species.

Wood and bark lignin contents of trees from deciduous forests of eastern India

Lignin is a polyphenolic compound found in plant tissues, especially wood and bark. The lignin content determines the quality of wood biochar in agroecological uses, and is used in the production of synthetic resins and adhesives. Despite its importance in plant physiology and its agricultural and industrial utility, there exists a wide gap of knowledge of lignin contents of tropical hardwood trees of South Asia, except for a few species. We present here the first estimation of lignin content in wood and bark of 48 species from tropical deciduous forests of India. We show that some species are characterized by greater wood lignin (WL) compared with bark lignin (BL) content, contrary to the generalization held for hardwood trees, and suggest a plausible correspondence between the WL to BL ratio and timber quality.

Using charcoal, ATR FTIR and chemometrics to model the intensity of pyrolysis: Exploratory steps towards characterising fire events

This study describes a multivariate statistical model (derived using partial least squares regression, PLS-R) that derives charring intensity (reaction temperature and duration) from the attenuated total reflectance (ATR) Fourier Transform Infrared (FTIR) spectra of charcoal. Data for the model was obtained from a library of charcoal samples produced under laboratory conditions at charring intensities (CI) relevant to wildfires and a series of feedstocks representing common tree species collected from Australia. The PLS-R model developed reveals the potential of FTIR to determine the charring intensity of charcoal. Though limited by the differences between laboratory-produced charcoal and the more heterogeneous and less-structured charcoal produced in a wildfire, the method was tested against fossil charcoal from a well-dated sediment core collected from Thirlmere Lakes National Park, Australia and showed a distinct change in CI that can be related to other climatic and environmental proxies. We suggest that the method has the potential to offer insights into the conditions under which natural charcoal is formed including the modelling of charring intensities of fossil charcoal samples isolated from sediments, archaeological applications or characterisation of contemporary fire events from charcoal in soils.

Multi-omics analyses on Kandelia obovata reveal its response to transplanting and genetic differentiation among populations

BACKGROUND

Restoration through planting is the dominant strategy to conserve mangrove ecosystems. However, many of the plantations fail to survive. Site and seeding selection matters for planting. The process of afforestation, where individuals were planted in a novel environment, is essentially human-controlled transplanting events. Trying to deepen and expand the understanding of the effects of transplanting on plants, we have performed a seven-year-long reciprocal transplant experiment on Kandelia obovata along a latitudinal gradient.

RESULTS

Combined phenotypic analyses and next-generation sequencing, we found phenotypic discrepancies among individuals from different populations in the common garden and genetic differentiation among populations. The central population with abundant genetic diversity and high phenotypic plasticity had a wide plantable range. But its biomass was reduced after being transferred to other latitudes. The suppressed expression of lignin biosynthesis genes revealed by RNA-seq was responsible for the biomass reduction. Moreover, using whole-genome bisulfite sequencing, we observed modification of DNA methylation in MADS-box genes that involved in the regulation of flowering time, which might contribute to the adaptation to new environments.

CONCLUSIONS

Taking advantage of classical ecological experiments as well as multi-omics analyses, our work observed morphology differences and genetic differentiation among different populations of K. obovata, offering scientific advice for the development of restoration strategy with long-term efficacy, also explored phenotypic, transcript, and epigenetic responses of plants to transplanting events between latitudes.

Mushroom Ligninolytic Enzymes―Features and Application of Potential Enzymes for Conversion of Lignin into Bio-Based Chemicals and Materials

Mushroom ligninolytic enzymes are attractive biocatalysts that can degrade lignin through oxido-reduction. Laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase are the main enzymes that depolymerize highly complex lignin structures containing aromatic or aliphatic moieties and oxidize the subunits of monolignol associated with oxidizing agents. Among these enzymes, mushroom laccases are secreted glycoproteins, belonging to a polyphenol oxidase family, which have a powerful oxidizing capability that catalyzes the modification of lignin using synthetic or natural mediators by radical mechanisms via lignin bond cleavage. The high redox potential laccase within mediators can catalyze the oxidation of a wide range of substrates and the polymerization of lignin derivatives for value-added chemicals and materials. The chemoenzymatic process using mushroom laccases has been applied effectively for lignin utilization and the degradation of recalcitrant chemicals as an eco-friendly technology. Laccase-mediated grafting has also been employed to modify lignin and other polymers to obtain novel functional groups able to conjugate small and macro-biomolecules. In this review, the biochemical features of mushroom ligninolytic enzymes and their potential applications in catalytic reactions involving lignin and its derivatives to obtain value-added chemicals and novel materials in lignin valorization are discussed.

Mechanics Design in Cellulose-Enabled High-Performance Functional Materials

The abundance of cellulose found in natural resources such as wood, and the wide spectrum of structural diversity of cellulose nanomaterials in the form of micro-nano-sized particles and fibers, have sparked a tremendous interest to utilize cellulose's intriguing mechanical properties in designing high-performance functional materials, where cellulose's structure-mechanics relationships are pivotal. In this progress report, multiscale mechanics understanding of cellulose, including the key role of hydrogen bonding, the dependence of structural interfaces on the spatial hydrogen bond density, the effect of nanofiber size and orientation on the fracture toughness, are discussed along with recent development on enabling experimental design techniques such as structural alteration, manipulation of anisotropy, interface and topology engineering. Progress in these fronts renders cellulose a prospect of being effectuated in an array of emerging sustainable applications and being fabricated into high-performance structural materials that are both strong and tough.

Genome reduction and relaxed selection is associated with the transition to symbiosis in the basidiomycete genus Podaxis

Insights into the genomic consequences of symbiosis for basidiomycete fungi associated with social insects remain sparse. Capitalizing on viability of spores from centuries-old herbarium specimens of free-living, facultative, and specialist termite-associated Podaxis fungi, we obtained genomes of 10 specimens, including two type species described by Linnaeus >240 years ago. We document that the transition to termite association was accompanied by significant reductions in genome size and gene content, accelerated evolution in protein-coding genes, and reduced functional capacities for oxidative stress responses and lignin degradation. Functional testing confirmed that termite specialists perform worse under oxidative stress, while all lineages retained some capacity to cleave lignin. Mitochondrial genomes of termite associates were significantly larger; possibly driven by smaller population sizes or reduced competition, supported by apparent loss of certain biosynthetic gene clusters. Our findings point to relaxed selection that mirrors genome traits observed among obligate endosymbiotic bacteria of many insects.

Value-Added Use of Invasive Plant-Derived Fibers as PHBV Fillers for Biocomposite Development

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising biobased, biodegradable thermoplastic with limited industrial applications due to its brittleness and high cost. To improve these properties, lignocellulosic fibers from two invasive plants (Phalaris arundinacea and Lonicera japonica) were used as PHBV reinforcing agents. Alkali treatment of the fibers improved the PHBV-fiber interfacial bond by up to 300%. The morphological, mechanical, and thermal properties of the treated fibers were characterized, as well as their size, loading, and type, to understand their impact on performance of the biocomposites. The new biocomposites had improved thermal stability, restricted crystallization, reduced rigidity, and reduced cost compared with PHBV. Additionally, these novel biocomposites performed similarly to conventional plastics such as polypropylene, suggesting their potential as bio-alternatives for industrial applications such as semirigid packaging and lightweight auto body panels.

Transcriptional reprogramming of xylem cell wall biosynthesis in tension wood

Tension wood (TW) is a specialized xylem tissue developed under mechanical/tension stress in angiosperm trees. TW development involves transregulation of secondary cell wall genes, which leads to altered wood properties for stress adaptation. We induced TW in the stems of black cottonwood (Populus trichocarpa, Nisqually-1) and identified two significantly repressed transcription factor (TF) genes: class B3 heat-shock TF (HSFB3-1) and MYB092. Transcriptomic analysis and chromatin immunoprecipitation (ChIP) were used to identify direct TF-DNA interactions in P. trichocarpa xylem protoplasts overexpressing the TFs. This analysis established a transcriptional regulatory network in which PtrHSFB3-1 and PtrMYB092 directly activate 8 and 11 monolignol genes, respectively. The TF-DNA interactions were verified for their specificity and transactivator roles in 35 independent CRISPR-based biallelic mutants and overexpression transgenic lines of PtrHSFB3-1 and PtrMYB092 in P. trichocarpa. The gene-edited trees (mimicking the repressed PtrHSFB3-1 and PtrMYB092 under tension stress) have stem wood composition resembling that of TW during normal growth and under tension stress (i.e., low lignin and high cellulose), whereas the overexpressors showed an opposite effect (high lignin and low cellulose). Individual overexpression of the TFs impeded lignin reduction under tension stress and restored high levels of lignin biosynthesis in the TW. This study offers biological insights to further uncover how metabolism, growth, and stress adaptation are coordinately regulated in trees.

Arabidopsis SnRK1 negatively regulates phenylpropanoid metabolism via Kelch domain-containing F-box proteins

Phenylpropanoid metabolism represents a substantial metabolic sink for photosynthetically fixed carbon. The evolutionarily conserved Sucrose Non-Fermenting Related Kinase 1 (SnRK1) is a major metabolic sensor that reprograms metabolism upon carbon deprivation. However, it is not clear if and how the SnRK1-mediated sugar signaling pathway controls phenylpropanoid metabolism. Here, we show that Arabidopsis SnRK1 negatively regulates phenylpropanoid biosynthesis via a group of Kelch domain-containing F-box (KFB) proteins that are responsible for the ubiquitination and degradation of phenylalanine ammonia lyase (PAL). Downregulation of AtSnRK1 significantly promoted the accumulation of soluble phenolics and lignin polymers and drastically increased PAL cellular accumulation but only slightly altered its transcription level. Co-expression of SnRK1α with PAL in Nicotiana benthamiana leaves resulted in the severe attenuation of the latter's protein level, but protein interaction assays suggested PAL is not a direct substrate of SnRK1. Furthermore, up or downregulation of AtSnRK1 positively affected KFB^PALs gene expression, and energy starvation upregulated KFB^PAL expression, which partially depends on AtSnRK1. Collectively, our study reveals that SnRK1 negatively regulates phenylpropanoid biosynthesis, and KFB^PALs act as regulatory components of the SnRK1 signaling network, transcriptionally regulated by SnRK1 and subsequently mediate proteasomal degradation of PAL in response to the cellular carbon availability.

Identification of monocot chimeric jacalin family reveals functional diversity in wheat

MAIN CONCLUSION

46 monocot chimeric jacalins (MCJs) were mined from wheat genome. They were divided into three subfamilies with the activity of mannose-specific lectins and had effects on dehydration tolerance or disease resistance. Monocot chimeric jacalin (MCJ) is a newly identified subfamily of plant lectins that exclusively exists in Poaceae. The MCJs are modular proteins consisting of a dirigent domain and a jacalin-related lectin domain. Their unique evolution and various functions are not fully understood as only few members of MCJ have so for been investigated. From wheat, 46 MCJs were identified and phylogenetically classified into three subfamilies, in which subfamily I represented the early evolutionary cluster. MCJ genes are evenly distributed among three subgenomes of wheat, indicating that MCJ might be an ancient gene in Poaceae. qRT-PCR analysis showed that TaMCJ1 and TaMCJ2 were mainly expressed in leaves while TaMCJ3 in root tissues. All these TaMCJ genes are JA or ABA inducible. All three proteins exhibited agglutinating activity but different preference to mannose-binding. The overexpression of TaMCJ3 in tobacco increased dehydration tolerance, while TaMCJ1 enhanced wildfire disease resistance. The lignin biosynthetic genes were temporarily induced after pathogen inoculation in transgenic tobacco overexpressing TaMCJ, but the specific association with TaMCJ was not established. This evidence argued against the notion that the dirigent domain in TaMCJ is directly linked with lignin metabolism. Taken together, these results pave the way for a better understanding of the manifold functionality of MCJs and offer important insights to the evolutionary history of MCJ.

Characterization of a High Hierarchical Regulator, PtrGATA12, Functioning in Differentially Regulating Secondary Wall Component Biosynthesis in Populus trichocarpa

In plants, GATA transcription factors (TFs) have been reported to play vital roles in to a wide range of biological processes. To date, there is still no report about the involvement and functions of woody plant GATA TFs in wood formation. In this study, we described the functional characterization of a Populus trichocarpa GATA TF, PtrGATA12, which encodes a nuclear-localized transcriptional activator predominantly expressing in developing xylem tissues. Overexpression of PtrGATA12 not only inhibited growths of most phenotypic traits and biomass accumulation, but also altered the expressions of some master TFs and pathway genes involved in secondary cell wall (SCW) and programmed cell death, leading to alternated SCW components and breaking forces of stems of transgenic lines. The significant changes occurred in the contents of hemicellulose and lignin and SCW thicknesses of fiber and vessel that increased by 13.5 and 10.8%, and 20.83 and 11.83%, respectively. Furthermore, PtrGATA12 bound directly to the promoters of a battery of TFs and pathway genes and activated them; the binding sites include two cis-acting elements that were specifically enriched in their promoter regions. Taken together, our results suggest PtrGATA12, as a higher hierarchical TF on the top of PtrWND6A, PtrWND6B, PtrMYB152, and PtrMYB21, exert a coordinated regulation of SCW components biosynthesis pathways through directly and indirectly controlling master TFs, middle-level TFs, and further downstream pathway genes of the currently known hierarchical transcription network that governs SCW formation.

Solvolysis of Kraft Lignin to Bio-Oil: A Critical Review

Lignin, a component of lignocellulosic biomass, is abundant and is produced extensively as a waste product of the Kraft pulping process, lignin obtained from this process is called Kraft lignin (KL). Lignin’s three-dimensional structure composed of aromatic alcohols (monolignols) makes it a potential source of renewable aromatic chemicals or bio-oil, if depolymerized. Among all the depolymerization methods for KL, solvolysis is the most popular, showing consistently high bio-oil yields. Despite the large number of studies that have been carried out, an economically feasible industrial process has not been found and comparison among the various studies is difficult, as very different studies in terms of reaction media and catalysts report seemingly satisfactory results. In this review, we compare and analyze KL solvolysis studies published, identify trends in bio-oil composition and give a comprehensive explanation about the mechanisms involved in the processes. Additional commentary is offered about the availability and future potential of KL as a renewable feedstock for aromatic chemicals, as well as logistical and technical aspects.

Combined forest and soil management after a catastrophic event

At the end of October 2018, a storm of unprecedented strength severely damaged the forests of the eastern sector of the Italian Alps. The affected forest area covers 42,500 ha. The president of one of the damaged regions asked for help from the University of Padua. After eight months of discussion, the authors of this article wrote a consensus text. The sometimes asper debate brought to light some crucial aspects: 1) even experienced specialists may have various opinions based on scientific knowledge that lead to conflicting proposals for action. For some of them there is evidence that to restore a destroyed natural environment it is more judicious to do nothing; 2) the soil corresponds to a living structure and every ecosystem's management should be based on it; 3) faced with a catastrophe, people and politicians find themselves unarmed, also because they rarely have the scientific background to understand natural processes. Yet politicians are the only persons who make the key decisions that drive the economy in play and therefore determine the near future of our planet. This article is an attempt to respond directly to a governor with a degree in animal production science, who formally and prudently asked a university department called "Land, Environment, Agriculture and Forestry" for help before taking decisions; 4) the authors also propose an artistic interpretation of facts (uncontrolled storm) and conclusions (listen to the soil). Briefly, the authors identify the soil as an indispensable source for the renewal of the destroyed forest, give indications on how to prepare a map of the soils of the damaged region, and suggest to anchor on this soil map a series of silvicultural and soil management actions that will promote the soil conservation and the faster recovery of the natural dynamic stability and resilience.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available for this article at 10.1007/s11629-019-5890-0 and is accessible for authorized users.

SINGLE FLOWER TRUSS and SELF-PRUNING signal developmental and metabolic networks to guide cotton architectures

Patterns of indeterminate and determinate growth specify plant architecture and influence crop productivity. In cotton (Gossypium hirsutum), SINGLE FLOWER TRUSS (SFT) stimulates the transition to flowering and determinate growth, while its closely related antagonist SELF-PRUNING (SP) maintains meristems in indeterminate states to favor vegetative growth. Overexpressing GhSFT while simultaneously silencing GhSP produces highly determinate cotton with reduced foliage and synchronous fruiting. These findings suggest that GhSFT, GhSP, and genes in these signaling networks hold promise for enhancing 'annualized' growth patterns and improving cotton productivity and management. To identify the molecular programs underlying cotton growth habits, we used comparative co-expression networks, differential gene expression, and phenotypic analyses in cotton varieties expressing altered levels of GhSFT or GhSP. Using multiple cotton and tomato datasets, we identified diverse genetic modules highly correlated with SFT or SP orthologs which shared related Gene Ontologies in different crop species. Notably, altering GhSFT or GhSP levels in cotton affected the expression of genes regulating meristem fate and metabolic pathways. Further phenotypic analyses of gene products involved in photosynthesis, secondary metabolism, and cell wall biosynthesis showed that early changes in GhSFT and GhSP levels profoundly impacted later development in distal tissues. Identifying the molecular underpinnings of GhSFT and GhSP activities emphasizes their broad actions in regulating cotton architecture.