Reduced Lignin Content Research Articles

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.

Genetic improvement of low-lignin poplars: a new strategy based on molecular recognition, chemical reactions and empirical breeding.

As an important source of pollution in the papermaking process, the presence of lignin in poplar can seriously affect the quality and process of pulping. During lignin synthesis, Caffeoyl-CoA-O methyltransferase (CCoAOMT), as a specialized catalytic transferase, can effectively regulate the methylation of caffeoyl-coenzyme A (CCoA) to feruloyl-coenzyme A. Targeting CCoAOMT, this study investigated the substrate recognition mechanism and the possible reaction mechanism, the key residues of lignin binding were mutated and the lignin content was validated by deep convolutional neural-network model based on genome-wide prediction (DCNGP). The molecular mechanics results indicate that the binding of S-adenosyl methionine (SAM) and CCoA is sequential, with SAM first binding and inducing inward constriction of the CCoAOMT; then CCoA binds to the pocket, and this process closes the outer channel, preventing contamination by impurities and ensuring that the reaction proceeds. Next, the key residues in the recognition process of SAM (F69 and D91) and CCoA (I40, N170, Y188 and D218) were analyzed, and we identified that K146 as a base catalyst is important for inducing the methylation reaction. Immediately after that, the possible methylation reaction mechanism was deduced by the combination of Restrained Electrostatic Potential (RESP) and Independent Gradient Model (IGM) analysis, focusing on the catalytic center electron cloud density and RESP charge distribution. Finally, the DCNGP results verified that the designed mutant groups were all able to effectively reduce the lignin content and increase the S-lignin content/ G-lignin content ratio, which was beneficial for the subsequent lignin removal. Multifaceted consideration of factors that reduce lignin content and combined deep learning to screen for favorable mutations in target traits provides new ideas for targeted breeding of low-lignin poplars.

RNAi-mediated downregulation of endogenous 4-coumarate: CoA ligase activity in Sorghum bicolor to alter the lignin content, which augmented the carbohydrate content and growth.

This study seeks to improve the biomass extractability of Sorghum bicolor by targeting a critical enzyme, 4CL, through metabolic engineering of the lignin biosynthetic pathway at the post-transcriptional level. Sorghum bicolor L., a significant forage crop, offers a potential source of carbohydrate components for biofuel production. The high lignin content in sorghum stems often impedes the extractability of desired carbohydrate components for industrial use. Thus, the present study aimed to develop an improved variety of S. bicolor with reduced lignin through RNA interference of the endogenous 4-coumarate:CoA ligase (4CL) gene involved in the lignin biosynthetic pathway. The S. bicolor gene was isolated, characterized, and used to construct the RNAi-inducing hpRNA gene-silencing construct. Two independent transgenic sorghum lines were produced by introducing an hpRNA-induced gene-silencing cassette of the Sb4CL through Agrobacterium-mediated transformation in the shoot tips of S. bicolor. This was confirmed by PCR amplification of the hygromycin-resistance gene and Southern hybridization. The Sb4CL gene transcript and its enzymatic activity were found to reduce to varying degrees, as shown by northern hybridization and enzyme activity in the independent transgenic samples. Endogenous Sb4CL downregulation in sorghum stem tissue correlates with reduced lignin content to a maximum range of 25%. The transfer of the transgene in the second generation was also analyzed. Decreased lignin content in the transgenic lines was compensated by increased total cell wall carbohydrates such as cellulose (36.56%) and soluble sugars (59.72%) compared to untransformed plants. The study suggests that suppressing the Sb4CL gene effectively develops better sorghum varieties with lower lignin content. This can be useful for industrial purposes, as the enhanced carbohydrate content and favorable alteration of lignin content can lead to economic benefits.

Transcriptome Analysis Reveals Key Pathways and Genes Involved in Lodging Resistance of Upland Cotton

Lodging resistance is one of the most important traits of machine-picked cotton. Lodging directly affects the cotton yield, quality and mechanical harvesting effect. However, there are only a few reports on the lodging resistance of cotton. In this study, the morphological and physiological characteristics and transcriptome of two upland cotton varieties with different lodging resistance were compared. The results showed that the stem strength; the contents of lignin, soluble sugar and cellulose; and the activities of several lignin biosynthesis-related enzymes of the lodging-resistant variety M153 were significantly higher than those of the lodging-susceptible variety M5330. Transcriptomic analysis showed that the expression level of several genes related to lignin, cellulose, starch and sucrose synthesis, and photosynthesis were significantly up-regulated in the lodging-resistant variety M153, which was consistent with the content determination results of lignin, cellulose and soluble sugar. Silencing two lignin biosynthesis-related genes (GhPAL and Gh4CL) in cotton via VIGS (Virus-Induced Gene Silencing) resulted in reduced lignin content and decreased lodging resistance in cotton. These results suggested that lignin, cellulose and soluble sugar contents were positively correlated with the lodging resistance of cotton, and lignin, cellulose and soluble sugar biosynthesis-related genes can be used as potential targets for improving the lodging resistance of cotton. These findings provide a theoretical basis for the cultivation of cotton varieties with strong lodging resistance in the future.

Effect of Lignin Reduction in Ammoniated Corn Stover on In-Vitro Digestibility of Dry Matter and Organic Matter

Corn stover is an agricultural by-product with the potential to be ruminant feed; however, its utilization is often limited by its high lignin content, which impairs digestibility. This study aims to evaluate the effect of lignin content in corn stover following ammonia treatment with urea addition on dry matter digestibility (DMD) and organic matter digestibility (OMD). The research employed a Completely Randomized Design (CRD) with four urea doses (0%, 2%, 4%, 6%) and four replicates, using in-vitro analysis to assess DMD and OMD values. Data analysis was conducted using the SAS (Statistical Analysis System) application. The results showed that ammonia treatment effectively reduced lignin content from 8.61% in the control (T1) to 3.31% in the highest urea dose treatment (T4). Both DMD and OMD increased, with the highest values obtained in the 4% urea treatment (T3), where DMD was 60.26% and OMD was 65.47%. The significant reduction in lignin facilitated improved digestibility by loosening lignocellulose bonds, allowing rumen microbes to degrade fiber more efficiently. This study concludes that the decrease in lignin content due to the addition of urea at varying levels (0-6%) during the ammonia treatment of corn stover, from 8.61% to 3.31%, positively impacts the increase in DMD (from 45.87% to 60.26%) and OMD (from 52.53% to 65.47%). The 4% urea treatment produced the best digestibility results, with lignin content reduced to 3.58%, yielding the highest DMD and OMD values. Further research is needed to evaluate the impact of this treatment on rumen fermentation characteristics.

Optimization of Microwave-Assisted Organosolv Cellulose Recovery from Olive-Tree Pruning with Three Different Solvents

Research studies for cellulose recovery from lignocellulosic materials are essential in order to propose sustainable alternatives to harness residual biomasses, solving problems caused by their abundance and inadequate use. In this study, olive-tree pruning biomass has been subjected to different pretreatments with different organosolvents (acetone, ethanol, and γ-valerolactone) with microwave radiation assistance. The effect of operating parameters has been studied, considering specific ranges of variables values according to each experimental design but, in any case, located in the ranges of 33–67% (chemical compound concentration), 130–170 °C (temperature), 5–30 min (reaction time), and 1/20–1/5 (solid/liquid ratio, s/L). Based on the R2 and R2adj values (mostly above 0.97), the experimental data were adequately adjusted to four selected response variables: post-solids cellulose and lignin content apart from removal percentages of both structural components. The optimization process resulted in post-treatment solids with meaningful cellulose yields (higher than 84.7%) and reduced lignin content (lower than 4.2%). The best results were obtained using 66.5% acetone (155 °C, 8.4 min and s/L = 1/19), involving greater material deconstruction, a high percentage of delignification (96.7%), not very significant cellulose loss (29.4%), and a post-treatment solid consisting almost exclusively of cellulose (≈99%).

Development and validation of hydrophobic molded pulp nursery pots made of hemp hurd

Biodegradable nursery pots (BNPs) composed of 50 % hemp hurd and 50 % recycled cardboard fibers (w/w dry basis) were produced using a custom-built handheld molded pulp device. Milling followed by sequential peracetic acid and sodium hydroxide delignification treatment reduced lignin content of hemp hurd from 23.76 % to 2.39 %, liberating cellulose and hemicellulose fibers for enabling the formation of interfiber interactions in molded pulp formulations. Beeswax and precipitated calcium carbonate based hydrophobic coating at ∼10 μm thickness significantly enhanced hydrophobicity of the BNPs, as indicated by the surface contact and sliding angle of 116.25° and 34.82°, respectively. Anaerobic biodegradability of BNP was confirmed via carbon dioxide and methane gas accumulation measurements. Developed BNPs were successfully validated through an eleven week greenhouse planting trial. This study introduced a new biodegradable molded pulp formulation made from hemp hurd and validated its application as an alternative to single use plastic nursery pots for growing seedlings.

Influence of drying temperature on the properties of Colombian banana fibers for its potential use as reinforcement in composite materials

This study investigated the impact of drying temperature on the physicochemical and mechanical properties of banana pseudostem fibers sourced from the Cordoba region in Colombia. Banana fibers (BFs) were extracted through mechanical decortication from the banana pseudostem (BP) of the plant and subsequently oven-dried at temperatures of 40 °C and 90 °C. Six mathematical models were employed to analyze the drying behavior of the fibers. The density of the BFs was determined using the apparent density method, and their chemical composition was evaluated via bromatological analysis. Fiber diameter was measured using optical microscopy (OM). The BF samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), contact angle measurements, and tensile testing. The results indicated that noncellulosic materials were removed from the fibers when dried at 90 °C, as evidenced by alterations in thermal degradation and fiber surface morphology observed through TG and SEM, suggesting a reduction in lignin content. While drying temperature did not affect fiber stiffness or ductility, a correlation with fiber diameter was noted. Thinner fibers, ranging from 148 to 250 μm, exhibited increased tensile strength and Young’s modulus, attributed to a more compact microfibril arrangement.

Investigating the Variation between Lignin Content and the Fracture Characteristics in Capsicum annuum Mutant Stems

The cultivation of horticultural plants in controlled greenhouse environments is a pivotal practice in modern agriculture, offering the potential to enhance crop productivity and mitigate climate change effects. This study investigates the biomechanical properties and lignin content of various Capsicum annuum mutant lines—‘fragile-plant’ (frx), ‘tortuous internodi’ (tti), and ‘puffy-structured stem’ (pfi)—in comparison to a commercially established variety, ‘Garai Fehér’. We employed the acetyl bromide method to quantify lignin content and conducted three-point bending tests to assess rigidity in three distinct regions of the stem. Gene expression analysis of key lignin biosynthetic pathway genes (PAL, C4H, 4CL, CCoAOMT, CAD) was performed using qRT-PCR. The results revealed significant differences in lignin content and breaking force among the genotypes and stem regions. The tti mutants exhibited similar lignin content to the control but lower breaking strength, likely due to elongated internodes. The frx mutants showed uniformly reduced lignin content, correlating with their fragile stems. The pfi mutants displayed abnormally high lignin content in the top region yet demonstrated the lowest stem rigidity in every region. Overexpression of CAD and CCoAOMT was detected in the mutants in specific regions of the stem, suggesting alterations in lignin biosynthesis; however, we could not confirm the correlation between them. Our findings indicate that while lignin content generally correlates with stem rigidity, this trait is complex and influenced by more factors.

Impact of phenology, brown midrib (BMR), seed treatment, and herbivory on epicuticular wax content and fall armyworm (Spodoptera frugiperda) feeding in sorghum-sudangrass (Sorghum xdrummondii)

In crop production, management strategies have historically relied upon chemical control to mitigate insect pest pressures. As resistance to pesticides grows at an alarming rate, and as non-target effects are found more frequently, the search for sustainable, novel pest management strategies has become more important. Plants are equipped with diverse physical and chemical defenses against insect pests. Among these physical defenses, epicuticular waxes serve as an important first line of defense. Yet, how these chemical control methods such as seed treatment affects epicuticular waxes is underexplored. Brown midrib (BMR) is a host-plant trait from a recessive gene that affects the monolignol biosynthetic pathway, reducing lignin content, and presents as a gene of interest for evaluation as a form of pest management. Sorghum-sudangrass, Sorghum x drummondii, is an economically important forage crop with BMR; however, the effects of BMR have primarily been studied in animal agriculture and its effects on insects is largely unknown. In addition, how BMR affects epicuticular waxes is also unknown. This study aims to understand how the quantity of epicuticular wax in Sorghum x drummondii is affected by chemical control (seed treatments), BMR, phenological stages, and how wax affects a polyphagous, destructive pest, fall armyworm, Spodoptera frugiperda (FAW). Through wax quantification and FAW feeding induction and wax added artificial diet experiments, we show that while BMR and seed treatment does not affect wax content, plant phenology affects wax, and wax is induced by FAW feeding and has negative consequences for caterpillar growth.

Negative regulation of CcPAL2 gene expression by the repressor transcription factor CcMYB4-12 modulates lignin and capsaicin biosynthesis in Capsicum chinense fruits

Peppers globally renowned for their distinctive spicy flavor, have attracted significant research attention, particularly in understanding spiciness regulation. While the activator MYB's role in spiciness regulation is well-established, the involvement of repressor MYB factors remains unexplored. This study identified the MYB4 transcription factor through RNA-seq and genome-wide analysis as being associated with spiciness. Consequently, CcMYB4-2 and CcMYB4-12 were cloned from Hainan Huangdenglong peppers, both exhibiting nuclear subcellular localization. qRT-PCR analysis revealed that CcMYB4-2/4-12 had high expression levels during the accumulation period of capsaicin, but there were differences in their peak expression levels, which may be related to the formation of pepper spiciness. Heterologous expression in Arabidopsis thaliana resulted in significantly elevated CcMYB4-2/4-12 expression levels and reduced lignin content. In CcMYB4-2 silenced plants, PAL expression remained unchanged, while PAL expression significantly increased in CcMYB4-12 silenced plants, leading to elevated lignin content and reduced capsaicin content. Yeast one-hybrid (Y1H) and dual luciferase reporter assays (DLR) demonstrated that CcMYB4-2/4-12 inhibited the transcription of CcPAL2 by binding to its promoter. Notably, CcMYB4-12 exhibited more pronounced inhibition. Therefore, it is hypothesized that CcMYB4-12 plays a pivotal role in regulating lignin and capsaicin biosynthesis. This study elucidates the molecular mechanism of MYB4 binding to the PAL promoter, providing a foundational understanding for analyzing phenylpropanoid metabolism and its diverse branches. Key messageThrough functional verification analysis of the repressor CcMYB4, transcriptional regulation experiments revealed that CcMYB4 can bind to the CcPAL2 promoter, negatively regulating the capsaicin biosynthesis in Capsicum chinense fruits.

Overexpression of SlALC Increases Drought and Salt Tolerance and Affects Fruit Dehiscence in Tomatoes.

The bHLH transcription factors are important plant regulators against abiotic stress and involved in plant growth and development. In this study, SlALC, a gene coding for a prototypical DNA-binding protein in the bHLH family, was isolated, and SlALC-overexpression tomato (SlALC-OE) plants were generated by Agrobacterium-mediated genetic transformation. SlALC transgenic lines manifested higher osmotic stress tolerance than the wild-type plants, estimated by higher relative water content and lower water loss rate, higher chlorophyll, reducing sugar, starch, proline, soluble protein contents, antioxidant enzyme activities, and lower MDA and reactive oxygen species contents in the leaves. In SlALC-OE lines, there were more significant alterations in the expression of genes associated with stress. Furthermore, SlALC-OE fruits were more vulnerable to dehiscence, with higher water content, reduced lignin content, SOD/POD/PAL enzyme activity, and lower phenolic compound concentrations, all of which corresponded to decreased expression of lignin biosynthetic genes. Moreover, the dual luciferase reporter test revealed that SlTAGL1 inhibits SlALC expression. This study revealed that SlALC may play a role in controlling plant tolerance to drought and salt stress, as well as fruit lignification, which influences fruit dehiscence. The findings of this study have established a foundation for tomato tolerance breeding and fruit quality improvement.

Function Analysis of a Maize Endo-1,4-β-xylanase Gene ZmHSL in Response to High-Temperature Stress.

Rising temperature is a major threat to the normal growth and development of maize, resulting in low yield production and quality. The mechanism of maize in response to heat stress remains uncertain. In this study, a maize mutant Zmhsl-1 (heat sensitive leaves) with wilting and curling leaves under high temperatures was identified from maize Zheng 58 (Z58) mutant lines generated by ethyl methanesulfonate (EMS) mutagenesis. The Zmhsl-1 plants were more sensitive to increased temperature than Z58 in the field during growth season. The Zmhsl-1 plants had lower plant height, lower yield, and lower content of photosynthetic pigments. A bulked segregant analysis coupled with whole-genome sequencing (BSA-seq) enabled the identification of the corresponding gene, named ZmHSL, which encodes an endo-β-1,4-xylanase from the GH10 family. The loss-of-function of ZmHSL resulted in reduced lignin content in Zmhsl-1 plants, leading to defects in water transport and more severe leaf wilting with the increase in temperature. RNA-seq analysis revealed that the differentially expressed genes identified between Z58 and Zmhsl-1 plants are mainly related to heat stress-responsive genes and unfolded protein response genes. All these data indicated that ZmHSL plays a key role in lignin synthesis, and its defective mutation causes changes in the cell wall structure and gene expression patterns, which impedes water transport and confers higher sensitivity to high-temperature stress.

Lignin lite: Boosting plant power through selective downregulation.

SUMMARY STATEMENTThis article explores the dual benefits of reducing lignin content in plants, which streamlines biofuel production while maintaining robust defence mechanisms. It discusses how plants compensate for lower lignin levels through alternative defence strategies, recent biotechnological advances in lignin modification, and the implications for agriculture and industry.

Identification and Analysis of the Mechanism of Stem Mechanical Strength Enhancement for Maize Inbred Lines QY1.

Enhancing stalk strength is a crucial strategy to reduce lodging. We identified a maize inbred line, QY1, with superior stalk mechanical strength. Comprehensive analyses of the microstructure, cell wall composition, and transcriptome of QY1 were performed to elucidate the underlying factors contributing to its increased strength. Notably, both the vascular bundle area and the thickness of the sclerenchyma cell walls in QY1 were significantly increased. Furthermore, analyses of cell wall components revealed a significant increase in cellulose content and a notable reduction in lignin content. RNA sequencing (RNA-seq) revealed changes in the expression of numerous genes involved in cell wall synthesis and modification, especially those encoding pectin methylesterase (PME). Variations in PME activity and the degree of methylesterification were noted. Additionally, glycolytic efficiency in QY1 was significantly enhanced. These findings indicate that QY1 could be a valuable resource for the development of maize varieties with enhanced stalk mechanical strength and for biofuel production.

Characterization of cellulose nanocrystals from Zhombwe (Neorautanenia brachypus (harms) CA Sm.) bagasse.

Increased awareness of environmental pollution has changed focus to the use of biodegradable materials because they lack persistence in the environment. This article focused on the production of cellulose nanocrystals from Zhombwe, Neorautanenia brachypus (Harms) CA Sm. bagasse using steam explosion, alkaline treatment, bleaching, purification, and acid hydrolysis. The chemical composition after the treatments was determined using TAPPI standards. Further characterization was done using x-ray Diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The nanoscale dimensions and morphology of the extracted nanocrystals was determined through field emission scanning electron microscopy (FE-SEM). FTIR spectroscopy and DSC confirmed the removal of noncellulosic compounds. XRD revealed that N. brachypus bagasse contained cellulose type I, which partly endured morphological change to polymorph II after purification and hydrolysis. FE-SEM revealed elliptical to rod-shaped structures after acid hydrolysis, which had a mean length and width of 1103 nm and 597 nm respectively. TAPPI tests revealed that successive chemical treatments increased crystallinity by 29.7%, enriched cellulose content by 74.2%, reduced lignin content by 21.7%, and reduced hemicellulose to less than 1%. The semicrystalline nature of the material produced in our work is a promising candidate for swelling hydrogel applications in areas such as wound dressing, heavy metal removal, controlled drug delivery, agriculture, and sanitary products. Future studies may focus on surface modification of nanocrystals to improve their thermal stability and therefore expand their range for potential industrial applications.

Expression and function analysis of phenylalanine ammonia-lyase genes involved in Bamboo lignin biosynthesis.

Bamboo, renowned as the fastest-growing plant globally, matures within an astonishingly short period of 40-50 days from shoots, reaching heights of 10-20 meters. Moreover, it can be harvested for various uses within 3-5 years. Bamboo exhibits exceptional mechanical properties, characterized by high hardness and flexibility, largely attributed to its lignin content. Phenylalanine ammonia-lyase (PAL) catalyzes the crucial initial step in lignin biosynthesis, but its precise role in bamboo lignification processes remains elusive. Thus, elucidating the functions of PAL genes in bamboo lignification processes is imperative for understanding its rapid growth and mechanical strength. Here, we systematically identified and classified PAL genes in Moso bamboo, ensuring nomenclature consistency across prior studies. Subsequently, we evaluated PAL gene expression profiles using publicly available transcriptome data. The downregulation of PePALs expression in Moso bamboo through in planta gene editing resulted in a decrease in PAL activity and a subsequent reduction in lignin content. In contrast, overexpression of PePAL led to enhanced PAL activity and an increase in lignin content. These findings highlight the critical role of PAL in the lignin biosynthesis process of Moso bamboo, which will help to unravel the mechanism underpinning bamboo's rapid growth and mechanical strength, with a specific emphasis on elucidating the functions of PAL genes.

Salt stress alters the cell wall components and structure in Miscanthus sinensis stems.

Miscanthus is a perennial grass suitable for the production of lignocellulosic biomass on marginal lands. The effects of salt stress on Miscanthus cell wall composition and its consequences on biomass quality have nonetheless received relatively little attention. In this study, we investigated how exposure to moderate (100 mM NaCl) or severe (200 mM NaCl) saline growing conditions altered the composition of both primary and secondary cell wall components in the stems of 15 Miscanthus sinensis genotypes. The exposure to stress drastically impacted biomass yield and cell wall composition in terms of content and structural features. In general, the observed compositional changes were more pronounced under severe stress conditions and were more apparent in genotypes with a higher sensitivity towards stress. Besides a severely reduced cellulose content, salt stress led to increased pectin content, presumably in the form of highly branched rhamnogalacturonan type I. Although salt stress had a limited effect on the total lignin content, the acid-soluble lignin content was strongly increased in the most sensitive genotypes. This effect was also reflected in substantially altered lignin structures and led to a markedly reduced incorporation of syringyl subunits and p-coumaric acid moieties. Interestingly, plants that were allowed a recovery period after stress ultimately had a reduced lignin content compared to those continuously grown under control conditions. In addition, the salt stress-induced cell wall alterations contributed to an improved enzymatic saccharification efficiency.

EuMYB308 regulates lignin accumulation by targeting EuLAC17 in Eucalyptus urophylla

It is known that laccase genes are involved in lignin synthesis. Eucalyptus is an important timber species; functional studies of specific laccase members and their upstream regulatory factors in Eucalyptus are incomplete, and the mechanism of lignin content variation in polyploid plants remains unclear. Therefore, in this study, we investigated the function of EuLAC17 by overexpressing it in tobaccos and the result showed the lignin content in transgenic tobacco increased significantly. Further, yeast one hybrid sequencing was used to identify a series of potential regulatory factors of EuLAC17, among which EuMYB308 showed the most significant correlation with EuLAC17. Yeast one hybrid, dual-luciferase reporter gene assay and electrophoretic mobility shift assay jointly verified that EuMYB308 could directly target the EuLAC17 promoter and repress its expression. In addition, overexpression of EuMYB308 resulted in significant reductions in plant growth, xylem cell lumen area, cell wall thickness and lignin content. Transcriptome sequencing showed that lignin biosynthesis genes including laccase genes were significantly differential expression in transgenic plants compared with wild-type plants. In triploid Eucalyptus urophylla, the expression of EuMYB308 was significantly upregulated, which may enhance the inhibition of EuLAC17 and thus reduce its expression level in triploid, which is one possible reason for the reduced lignin content in triploid E. urophylla. This study provides important insights into transcriptional regulation of lignin biosynthesis in Eucalyptus, and also contributes to revealing the genetic mechanism of lignin content variation in polyploid plants, which are of great significance for promoting the improvement of wood quality in forest trees and polyploid breeding.

Nutritional upgrade of olive mill stone waste, walnut shell and their mixtures by applying solid state fermentation initiated by Pleurotus ostreatus

Present study concerns the transformation of the agro-industrial by-products olive mill stone waste (OMSW) and walnut shell (WS) to a protein-enriched animal feedstuff utilizing the solid state fermentation (SSF) technique. For this purpose, various mixtures of these by-products were exploited as substrates of the SSF process which was initiated by the P. ostreatus fungus. The respective results indicated that the substrate consisted of 80% WS and 20% OMSW afforded the product with the highest increase in protein content, which accounted the 7.57% of its mass (69.35% increase). In addition, a 26.13% reduction of lignin content was observed, while the most profound effect was observed for their 1,3–1,6 β-glucans profile, which was increased by 3-folds reaching the 6.94% of substrate’s mass. These results are indicative of the OMSW and WS mixtures potential to act as efficient substrate for the development of novel proteinaceous animal feed supplements using the SSF procedure. Study herein contributes to the reintegration of the agro-industrial by-products aiming to confront the problem of proteinaceous animal feed scarcity and reduce in parallel the environmental footprint of the agro-industrial processes within the context of circular economy.