Lignin Synthesis Research Articles

Synthesis and Antibacterial Properties of Novel Quaternary Ammonium Lignins.

The ongoing demand for effective antimicrobial materials persists, and lignin emerges as a promising natural antibacterial material with renewable properties. The adaptability of lignin to various chemical modifications offers avenues to enhance its antimicrobial activity. Here, we employed chloromethylation and subsequent functionalization with variable tertiary N-alkyl dimethyl amines to produce C6-C18 quaternary ammonium lignins (QALs) from hardwood (aspen), softwood (pine), and grass (barley straw). Successful synthesis of QALs was confirmed through NMR and FTIR analysis results along with an increase in the surface ζ-potential. Antibacterial activity of QALs against clinical strains of Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus was assessed using minimal bactericidal concentration (MBC) assay and agar growth inhibition zone (ZOI) test. The antibacterial activity of QALs was found to be higher than that of the unmodified lignins. QALs with longer alkyl chains demonstrated an MBC of 0.012 mg/L against K. pneumoniae already after 1 h of exposure with similar effect size reached after 24 h for S. aureus. For all the lignins, an increase in alkyl chain length resulted in an increase in their bactericidal activity. MBC values of C14-C18 QALs were consistently lower than the MBC values of QALs with shorter alkyl chains. Besides the alkyl chain length, MBC values of barley and pine QALs were negatively correlated with the surface ζ-potential. While alkyl chain length was one of the key properties affecting the MBC values in a liquid-based test, the agar-based ZOI test demonstrated an antibacterial optimum of QALs at C12-C14, likely due to limited diffusion of QALs with longer alkyl chains in a semisolid medium.

Transcription Factor VlbZIP14 Inhibits Postharvest Grape Berry Abscission by Directly Activating VlCOMT and Promoting Lignin Biosynthesis.

Sulfur dioxide (SO2) is the most effective preservative for table grapes as it reduces the respiratory intensity of berries and inhibits mold growth. However, excessive SO2 causes berry abscission during storage, resulting in an economic loss postharvest. In this study, grapes were exogenously treated with SO2, SO2 + 1.5% chitosan, SO2 + 1.5% eugenol, and SO2 + eugenol-loaded chitosan nanoparticles (SN). In comparison to SO2 treatment, SN treatment reduced the berries' abscission rate by 74% while maintaining the quality of the berries. Among the treatments, SN treatment most effectively inhibited berry abscission and maintained berry quality. RNA-sequencing (RNA-seq) revealed that SN treatment promoted the expression of genes related to cell wall metabolism. Among these genes, VlCOMT was detected as the central gene, playing a key role in mediating the effects of SN. Dual luciferase and yeast one-hybrid (Y1H) assays demonstrated that VlbZIP14 directly activated VlCOMT by binding to the G-box motif in the latter's promoter, which then participated in lignin synthesis. Our results provide key insights into the molecular mechanisms underlying the SN-mediated inhibition of berry abscission and could be used to improve the commercial value of SO2-treated postharvest table grapes.

Mining Candidate Genes for Leaf Angle in Brassica napus L. by Combining QTL Mapping and RNA Sequencing Analysis.

Leaf angle (LA) is an important trait of plant architecture, and individuals with narrow LA can better capture canopy light under high-density planting, which is beneficial for increasing the overall yield per unit area. To study the genetic basis and molecular regulation mechanism of leaf angle in rapeseed, we carried out a series of experiments. Quantitative trait loci (QTL) mapping was performed using the RIL population, and seven QTLs were identified. Transcriptome analysis showed that the cell wall formation/biogenesis processes and biosynthesis/metabolism of cell wall components were the most enrichment classes. Most differentially expressed genes (DEGs) involved in the synthesis of lignin, xylan, and cellulose showed down-regulated expression in narrow leaf material. Microscopic analysis suggested that the cell size affected by the cell wall in the junction area of the stem and petiole was the main factor in leaf petiole angle (LPA) differences. Combining QTL mapping and RNA sequencing, five promising candidate genes BnaA01G0125600ZS, BnaA01G0135700ZS, BnaA01G0154600ZS, BnaA10G0154200ZS, and BnaC03G0294200ZS were identified in rapeseed, and most of them were involved in cell wall biogenesis and the synthesis/metabolism of cell wall components. The results of QTL, transcriptome analysis, and cytological analysis were highly consistent, collectively revealing that genes related to cell wall function played a crucial role in regulating the LA trait in rapeseed. The study provides further insights into LA traits, and the discovery of new QTLs and candidate genes is highly beneficial for genetic improvement.

A GhLac1-centered transcriptional regulatory cascade mediates cotton resistance to Verticillium dahliae through the lignin biosynthesis pathway

The lignin biosynthesis pathway plays a crucial role in the defense response against V. dahliae in cotton, and it is essential to identify the key regulators in this pathway for disease-resistant breeding. In a previous study, the cotton laccase gene GhLac1 was identified as mediating plant broad-spectrum biotic stress tolerance by manipulating phenylpropanoid metabolism. However, the upstream master regulators and regulatory mechanism of lignin are still largely unknown. This study aims to identify the upstream regulators of GhLac1 and explore the molecular mechanism underlying cotton's disease resistance response to V. dahliae. Through the study, three WRKY, three MYB, and one APETALA2/ETHYLENE RESPONSIVE FACTOR (ERF) TFs were identified as differentially responding to V. dahliae infection in cotton. Among these TFs, GhWRKY30, GhWRKY41, GhMYB42, and GhTINY2 were found to directly bind to the GhLac1 promoter and activate its expression. Transient overexpression of these four TFs in cotton led to increased expression of GhLac1 and other the laccase family members, while knockdown of these TFs resulted in reduced lignin accumulation and increased susceptibility to V. dahliae. Additionally, GhWRKY30 and GhWRKY41 were observed to interact with themselves and with each other, synergistically transactivating the GhLac1 promoter. This study reveals a GhLac1-centered transcriptional regulatory cascade of lignin synthesis that contributes to cotton's defense response by modulating lignin metabolism.

Hydrogen Sulfide Improves Postharvest Quality of Okra (Abelmoschus esculentus (L.) Moench) Pods by Enhancing Antioxidant Capacity and Delaying Lignification.

Okra (Abelmoschus esculentus (L.) Moench) pod storage is challenging due to its high water content and tendency to lignify. Sodium hydrosulfide (NaHS) served as an H2S donor in this investigation. Compared with the control group, the group treated with 0.5 mmol/L NaHS solution effectively maintained the appearance quality, and its weight loss was only 6.21% at 20 days. The H2S treatment not only preserved tissue nutrients but also significantly enhanced catalase (CAT), ascorbic acid peroxidase (APX), and superoxide dismutase (SOD) activities while decreasing oxidant damage. In addition, H2S slowed down lignin synthesis by inhibiting the activities of key enzymes such as phenylalanine ammonialyase (PAL), cinnamate 4-hydroxylase (C4H), and cinnamyl alcohol dehydrogenase (CAD) in the lignin biosynthesis pathway. Transcriptome analysis revealed that H2S affects 34 genes in the phenylpropanoid biosynthesis pathway, such as AePAL, Ae4CL1, AeCCOAOMT1, AePOD, etc., which inhibit lignin synthesis of okra pods. All in all, moderate H2S can improve postharvest quality and extend the shelf-life of okra pods by enhancing antioxidant capacity and delaying lignification; the results will provide an overview of its application in the preservation of okra pods.

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.

Facile synthesis, release mechanism, and life cycle assessment of amine-modified lignin for bifunctional slow-release fertilizer

Biomass-based slow-release fertilizers (SRFs) are a sustainable solution for addressing food scarcity, improving fertilizer efficiency, and reducing pollution, whereas they still face complex preparation, high costs, and low release characteristics. This study introduces a simple and innovative approach to producing bifunctional green SRFs with controlled release and conditioning properties for saline soils and harsh environments. The method involves a one-pot preparation of microsphere-structured amine-modified lignin slow-release fertilizer (L-UX) using biomass lignin as the starting material. The L-UX demonstrates an exceptional fertilizer loading rate (66.2 %) and extended slow-release performance (288 h), effectively enhancing the fertilizer's release ability. Compared to traditional fertilizers, the bifunctional L-UX significantly improves soil water retention capacity (824.3 %), plant growth, and germination percentage in challenging soil conditions (133 %). These findings highlight the potential of L-UX as a large-scale controlled-release fertilizer in harsh environments. A life cycle assessment (LCA) was also conducted to evaluate the environmental impact of L-UX from its production to disposal. This revealed that L-UX has a minimal environmental footprint compared to conventional inorganic fertilizers. This study further supports the widespread application of L-UX as an environmentally friendly alternative.

Do leaf lignin content or leaf mass-to-area bias the estimation of intrinsic water use efficiency from leaf bulk δ13C? A test with seedlings from five oak species

Key MessageLeaves of seedlings from five oak species (Quercus robur L.; Q. pubescens L.; Q. suber L.; Q. afares Pomel; Q. ilex L.) displayed large, mainly inter-specific, differences in leaf mass-to-area ratio (LMA) and lignin content, as well as in the 13C composition of bulk leaf biomass. The variation in leaf lignin content and LMA did not impact the offset between the 13C composition measured in bulk leaf material versus soluble sugars. This observation, as well as the similar correlations between intrinsic leaf water use efficiency and the 13C compositions of bulk material or soluble sugars extracted from leaves, confirms their reliable use as a proxy for the former even when there is a large variation in LMA or lignin among samples.ContextCarbon isotope composition (δ13C) of bulk leaf biomass is frequently used as a proxy for intrinsic water use efficiency (iWUE) in large-scale intra- and inter-specific comparisons. However, post-photosynthetic 13C discrimination during the synthesis of lignin combined with differences in leaf mass-to-area ratio (LMA) may bias the relationship between δ13C of bulk leaf matter and iWUE and thus its use as a proxy of iWUE.AimsTo quantify the impact of differences in lignin content and LMA on the relationship between δ13C of bulk leaf biomass and iWUE over a large gradient of lignin contents across five oak species (deciduous: Quercus robur, Q. pubescens, Q. afares and evergreen: Q. ilex and Q. suber).MethodsWe measured lignin content, LMA, and δ13C of bulk leaf biomass and of soluble sugars extracted from the leaves, as well as intrinsic water use efficiency (derived from leaf gas exchange) in seedlings of the five oak species grown under common conditions in a greenhouse and measured in a climate chamber.ResultsThere was a large range (mainly across species) in lignin content (4 to 33%) and LMA (60–180 g m−2). δ13C of bulk leaf biomass and soluble sugars were tightly correlated, showing a significant mean offset of − 0.4‰. This offset was stable across species and not correlated to the lignin content of the leaves. A very loose correlation was found between the offset and LMA, mainly due to one species.ConclusionOur results are a demonstration that potential variations in leaf lignin content or LMA have no or only a little effect on the δ13C of bulk leaf biomass. They are unlikely to cause a bias when using bulk leaf δ13C as a proxy for variations in intrinsic water use efficiency among Mediterranean and temperate broad-leaf forest tree species.

Characterization of the Serine Protease TlSP1 from Trichoderma longibrachiatum T6 and Its Function in the Control of Heterodera avenae in Wheat.

Serine protease is an extracellular protease secreted by biocontrol fungi that can effectively control nematode diseases by degrading nematode eggshells and enhancing plant resistance. Trichoderma longibrachiatum T6, an important biocontrol fungus, has been demonstrated to effectively parasitize and degrade Heterodera avenae cysts, eggs, and second-stage juveniles (J2s). However, the genes that encoding serine protease and their functions in T. longibrachiatum T6 have not been thoroughly investigated. In this study, we successfully cloned and sequenced the serine protease gene TlSP1 in T. longibrachiatum T6. Our results revealed that the expression level of the TlSP1 gene was induced and significantly increased in T. longibrachiatum T6 after inoculation with H. avenae cysts. The full-length sequence of the coding region (CDS) of TlSP1 gene was 1230 bp and encoded a protein consisting of 409 amino acids. Upon the transformation of the TlSP1 gene into Pichia pastoris X33, the purified recombinant TlSP1 protein exhibited optimal activity at a temperature of 50 °C and pH 8.0. Following 4-10-day of treatment with the purified recombinant TlSP1 protein, the eggshells and content were dissolved and exuded. The number of nematodes invading wheat roots was reduced by 38.43% in the group treated with both TlSP1 and eggs on one side (P1+N) compared to the control group, while the number of nematodes invading wheat roots was reduced by 30.4% in the TlSP1 and eggs two-sided treatment group (P1/N). Furthermore, both the P1+N and P1/N treatments significantly upregulated genes associated with defense enzymes (TaPAL, TaCAT, TaSOD, and TaPOD), genes involved in the lignin synthesis pathway (TaC4H, Ta4CL2, TaCAD1, and TaCAD12), and salicylic acid (SA)-responsive genes (TaNPR1, TaPR1, and TaPR2) and led to the high expression of jasmonic acid (JA)-responsive genes (TaPR4, TaOPR3, and TaAOS2). This study has highlighted the significant role of the TlSP1 gene in facilitating H. avenae eggshells' dissolution, preventing nematode invasion in the host plant, and boosting plant resistance in wheat.

Transcriptomic and metabolomic analysis of quality deterioration of postharvest okra fruit at different storage temperatures

Okra fruit have short postharvest potential and are susceptible to chilling injury (CI). To increase our understanding of the metabolism of okra fruit we have analyzed the transcriptomic and metabolomic changes of the fruit stored at 4, 10, and 22 ℃ for six days. Compared with 0 d, storage at 22 °C for 6 days, senescence and lignification of fruit were associated with upregulation of genes related to abscisic acid (ABA) synthesis and signal transduction (ZEP, NCED, AAO, PYR/PYL, PP2C), lignin synthesis (HCT, 4CL, CCR, CAD, F5H, COMT), and cellulose synthesis (CesA). Chilling injury of okra at 4 ℃ may be caused by the activation of the α-linolenic acid metabolic pathway and flavonoid synthesis pathway, compromised membrane integrity, and higher reactive oxygen species levels. Storage at 10 ℃ resulted in the downregulation of ABA synthesis, signal transduction, and lignin synthesis genes, inhibition of α-linolenic acid pathway metabolites, and the expression of membrane lipid degradation genes (PLD, PLA, lipase, DGK, LOX). Conversely, there was an upregulation of antioxidant enzymes (APX, AO, POD, Grx, MDHAR) and genes involved in the flavonoid synthesis pathway (C4H, CHS, CHI, F3H, ANS), and with their corresponding metabolites (pinocembrin, butin, epiafzelechin, catechin). These changes were associated with slower fruit senescence, indicating that 10 ℃ better maintained the physiological quality of okra fruit after harvest. Based on these findings, a network model was established to control the postharvest quality of okra fruit under different temperature treatments. This study explored the regulatory mechanism of okra at different temperatures at the molecular level and laid a theoretical foundation for improving the quality of postharvest okra and extending its shelf life.

Intrinsic Mechanism of CaCl2 Alleviation of H2O2 Inhibition of Pea Primary Root Gravitropism.

Normal root growth is essential for the plant uptake of soil nutrients and water. However, exogenous H2O2 inhibits the gravitropic growth of pea primary roots. It has been shown that CaCl2 application can alleviate H2O2 inhibition, but the exact alleviation mechanism is not clear. Therefore, the present study was carried out by combining the transcriptome and metabolome with a view to investigate in depth the mechanism of action of exogenous CaCl2 to alleviate the inhibition of pea primordial root gravitropism by H2O2. The results showed that the addition of CaCl2 (10 mmol·L-1) under H2O2 stress (150 mmol·L-1) significantly increased the H2O2 and starch content, decreased peroxidase (POD) activity, and reduced the accumulation of sugar metabolites and lignin in pea primary roots. Down-regulated genes regulating peroxidase, respiratory burst oxidase, and lignin synthesis up-regulated PGM1, a key gene for starch synthesis, and activated the calcium and phytohormone signaling pathways. In summary, 10 mmol·L-1 CaCl2 could alleviate H2O2 stress by modulating the oxidative stress response, signal transduction, and starch and lignin accumulation within pea primary roots, thereby promoting root gravitropism. This provides new insights into the mechanism by which CaCl2 promotes the gravitropism of pea primary roots under H2O2 treatment.

Rapid synthesis of ferulic acid-derived lignin coated silver nanoparticles with low cytotoxicity and high antibacterial activity

Antibiotic resistance and the rise of untreatable bacterial infections pose severe threats to human health. Silver nanoparticles (AgNPs) have emerged as a promising antibacterial solution due to their broad-spectrum effectiveness. However, their relatively high cytotoxicity has limited their widespread application. In this study, ferulic acid (FA) was used as a reducing agent, while silver oxide served as a silver precursor to rapidly prepare FA-derived lignin (FAL) coated AgNPs (AgNPs@FAL) with a size ranging from 34.8 to 77.1 nm. Density functional theory (DFT) calculations indicated that the coating of FAL endowed AgNPs@FAL with high stability, preventing the oxidation of AgNPs prior to antibacterial applications. Cell experiments further indicated that AgNPs@FAL exhibited lower cell toxicity (∼80 % viability of normal kidney cells cultured at 25 μg/mL AgNPs@FAL) compared to fully exposed commercially available citrate-modified AgNPs (AgNPs@CA). Antibacterial experiments revealed that the minimum inhibitory concentrations (MIC) of AgNPs@FAL against E. coli and S. aureus were 12.5 μg/mL and 25 μg/mL, respectively, surpassing the antibacterial effect of AgNPs@CA, as well as ampicillin and penicillin. Additionally, AgNPs@FAL was capable of disrupting E. coli and S. aureus biofilm formation. This novel AgNPs@FAL formulation presents a promising antibacterial solution, addressing limitations observed in conventional drugs.

Effects of spraying cycocel and delaying nitrogen application on lodging resistance and yield formation of winter wheat.

We conducted a 3-year (2017-2020) field experiment in the wheat base of Jinzhong Agricultural Hi-tech Industries Demonstration Zone, aiming to determine the measures of nitrogen topdressing and the regulatory effect of cycocel in spring to increase wheat yield. Four nitrogen topdressing dates were set up under the condition of cycocel spraying and control (CK) during the rising period: 10 days (D10), 20 days (D20), 30 days (D30), and 40 days (D40) after regreening stage, to analyze the impact of different N topdressing dates on winter wheat yield and the regulation effect of cycocel on stem characteristics, lignin content and related synthetase activities. The results showed that compared to other nitrogen topdressing dates, D30 increased spike number by 1.4%-5.2%, grain number per spike by 0.4%-12.0%, 1000-grain weight by 1.7%-9.4% and yield 8.8%-22.1% respectively. Compared to D10 and D20, D30 significantly improved the activities of phenylalanine ammonia-lyase (PAL) at 0-21 days and 35-42 days after the formation of the second section and increased that of tyrosine ammonia-lyase (TAL) at 0-42 days after the formation of the second section, and increased the lignin content of stem, the internode quality, and the breaking resistance of stem, reduced plant height, and thereby improved the lodging resistance. However, D40 increased grain number per spike by 4.5%-10.1% and yield 0.04%-11.3%, but reduced the activities of PAL and TAL at 0-42 days after the formation of the second internode, reduced the lignin content, weakened the stem strength, and increased the risk of lodging. After spraying cycocel, plant height decreased significantly, the activities of PAL and TAL enhanced, the lignin content in internodes increased, the stem strength advanced, and reached a significant level under D30. Under the condition of nitrogen topdressing combined with cycocel spraying in spring, PAL and TAL activities were significantly positively correlated with lignin content. Lignin content was significantly positively correlated with stem breaking resistance. Stem breaking resistance was significantly positively correlated with lodging resistance index. Yield and its components were significantly posi-tively correlated with internode diameter, weight and breaking resistance, and significantly negatively correlated with plant height and internode length. Overall, nitrogen topdressing combined with spraying cycocel 30 days after regreening could promote the synthesis and accumulation of lignin, and improve stem plumpness, plant lodging resistance and yield.

Functional analysis of two caffeoyl-coenzyme 3 a-o-methyltransferase involved in pear lignin metabolism

Caffeoyl-coenzyme 3 A-O-methyltransferase (CCoAOMT) plays a crucial role in the lignin synthesis in many higher plants. In this study, nine PbCCoAOMT genes in total were identified from pear, and classified into six categories. We treated pear fruits with hormones abscisic acid (ABA) and methyl jasmonate (MeJA) and salicylic acid (SA) and observed differential expression levels of these genes. Through qRT-PCR, we also preliminarily identified candidate PbCCoAOMT gene, potentially involved in lignin synthesis in pear fruits. Additionally, the overexpression of PbCCoAOMT1/2 in Arabidopsis and pear fruits increased in lignin content. Enzymatic assays showed that recombinant PbCCoAOMT1/2 proteins have similar enzymatic activity in vitro. The Y1H (Yeast one-hybrid) and dual luciferase (dual-LUC) experiments demonstrated that PbMYB25 can bind to the AC elements in the promoter region of the PbCCoAOMT1 gene. Our findings suggested that the PbCCoAOMT1 and PbCCoAOMT2 genes may contribute to the synthesis of lignin and provide insights into the mechanism of lignin biosynthesis and stone cell development in pear fruits.

Overexpression of FERONIA receptor kinase MdMRLK2 regulates lignin accumulation and enhances water use efficiency in apple under long-term water deficit condition.

Water use efficiency (WUE) is crucial for apple tree fitness and survival, especially in response to climatic changes. The receptor-like kinase FERONIA is reportedly an essential regulator of plant stress responses, but its role in regulating WUE under water deficit conditions is unclear. Here, we found that overexpressing the apple FERONIA receptor kinase gene, MdMRLK2, enhanced apple WUE under long-term water deficit conditions. Under drought treatment, 35S::MdMRLK2 apple plants exhibited higher photosynthetic capacity and antioxidant enzyme activities than wild-type (WT) plants. 35S::MdMRLK2 apple plants also showed increased biomass accumulation, root activity, and water potential compared to WT plants. Moreover, MdMRLK2 physically interacts with and phosphorylates cinnamoyl-CoA reductase 1, MdCCR1, an enzyme essential for lignin synthesis, at position Ser260. This interaction likely contributed to increased vessel density, vascular cylinder area, and lignin content in 35S::MdMRLK2 apple plants under drought conditions. Therefore, our findings reveal a novel function of MdMRLK2 in regulating apple WUE under water deficit conditions.

How lignin biosynthesis responds to nitrogen in plants: ascoping review.

Nitrogen (N) plays a critical role in the functioning of key amino acids and synthetic enzymes responsible for the various stages of lignin biosynthesis. However, the precise mechanisms through which N influences lignin biosynthesis have not been fully elucidated. This scoping review explores how lignin biosynthesis responds to N in plants. A systematic search of the literature in several databases was conducted using relevant keywords. Only 44 of the 1842 selected studies contained a range of plant species, experimental conditions, and research approaches. Lignin content, structure, and biosynthetic pathways in response to N are discussed, and possible response mechanisms of lignin under low N are proposed. Among the selected studies, 64.52% of the studies reter to lignin content found a negative correlation between N availability and lignin content. Usually, high N decreases the lignin content, delays cell lignification, increases p-hydroxyphenyl propane (H) monomer content, and regulates lignin synthesis through the expression of key genes (PAL, 4CL, CCR, CAD, COMT, LAC, and POD) encoding miRNAs and transcription factors (e.g., MYB, bHLH). N deficiency enhances lignin synthesis through the accumulation of phenylpropanoids, phenolics, and soluble carbohydrates, and indirect changes in phytohormones, secondary metabolites, etc. This review provides new insights and important references for future studies on the regulation of lignin biosynthesis.

Exploring the nematicidal mechanisms and control efficiencies of oxalic acid producing Aspergillus tubingensis WF01 against root-knot nematodes.

Root-knot nematodes (RKN; Meloidogyne spp.) are among the highly prevalent and significantly detrimental pathogens that cause severe economic and yield losses in crops. Currently, control of RKN primarily relies on the application of chemical nematicides but it has environmental and public health concerns, which open new doors for alternative methods in the form of biological control. In this study, we investigated the nematicidal and attractive activities of an endophytic strain WF01 against Meloidogyne incognita in concentration-dependent experiments. The active nematicidal metabolite was extracted in the WF01 crude extract through the Sephadex column, and its structure was identified by nuclear magnetic resonance and mass spectrometry data. The strain WF01 was identified as Aspergillus tubingensis based on morphological and molecular characteristics. The nematicidal and attractive metabolite of A. tubingensis WF01 was identified as oxalic acid (OA), which showed solid nematicidal activity against M. incognita, having LC50 of 27.48 μg ml-1. The Nsy-1 of AWC and Odr-7 of AWA were the primary neuron genes for Caenorhabditis elegans to detect OA. Under greenhouse, WF01 broth and 200 μg ml-1 OA could effectively suppress the disease caused by M. incognita on tomatoes respectively with control efficiency (CE) of 62.5% and 70.83%, and promote plant growth. In the field, WF01-WP and 8% OA-WP formulations showed moderate CEs of 51.25%-61.47% against RKN in tomato and tobacco. The combined application of WF01 and OA resulted in excellent CEs of 66.83% and 69.34% toward RKN in tomato and tobacco, respectively. Furthermore, the application of WF01 broth or OA significantly suppressed the infection of J2s in tomatoes by upregulating the expression levels of the genes (PAL, C4H, HCT, and F5H) related to lignin synthesis, and strengthened root lignification. Altogether, our results demonstrated that A. tubingensis WF01 exhibited multiple weapons to control RKN mediated by producing OA to lure and kill RKN in a concentration-dependent manner and strengthen root lignification. This fungus could serve as an environmental bio-nematicide for managing the diseases caused by RKN.

Genome-Wide Identification, Evolution, and Expression Analysis of the DIR Gene Family in Schima superba.

Schima superba, commonly known as the Chinese guger tree, is highly adaptable and tolerant of poor soil conditions. It is one of the primary species forming the evergreen broad-leaved forests in southern China. Dirigent proteins (DIRs) play crucial roles in the synthesis of plant lignin and lignans, secondary metabolism, and response to adversity stress. However, research on the DIR gene family in S. superba is currently limited. This study identified 24 SsDIR genes, categorizing them into three subfamilies. These genes are unevenly distributed across 13 chromosomes, with 83% being intronless. Collinearity analysis indicated that tandem duplication played a more significant role in the expansion of the gene family compared to segmental duplication. Additionally, we analyzed the expression patterns of SsDIRs in different tissues of S. superba. The SsDIR genes exhibited distinct expression patterns across various tissues, with most being specifically expressed in the roots. Further screening identified SsDIR genes that may regulate drought stress, with many showing differential expression under drought stress conditions. In the promoter regions of SsDIRs, various cis-regulatory elements involved in developmental regulation, hormone response, and stress response were identified, which may be closely related to their diverse regulatory functions. This study will contribute to the further functional identification of SsDIR genes, providing insights into the biosynthetic pathways of lignin and lignans and the mechanisms of plant stress resistance.

Ultraviolet‐B Stress Increases Epidermal UV‐Screening Effectiveness and Alters Growth and Cell‐Wall Constituents of the Brown Midrib bmr6 and bmr12 Mutants of Sorghum bicolor

ABSTRACTThe brown midrib bmr6 and bmr12 mutants of sorghum (Sorghum bicolor) have alterations to the phenylpropanoid pathway impairing the activity of cinnamyl alcohol dehydrogenase (CAD) and/or caffeate5/hydroxyferulate O‐methyl transferase (COMT) enzymes, which inhibit lignin synthesis. Interestingly, these phenylpropanoids can also act as sunscreen compounds in plants and potentially attenuate ultraviolet radiation. We examined the effects of ultraviolet‐B (UV‐B; 280–320 nm) exclusion on growth, cell‐wall constituents and UV‐screening abilities of bmr6, bmr12, a double mutant (bmr6 bmr12; dm) and wild‐type (WT) genotypes of S. bicolor. Plants were grown in a UV‐transparent greenhouse under filters that either transmitted 2.8% (Mylar) or 90% (Aclar) of UV‐B. The greenhouse experiment was a 2 × 4 (UV treatment × genotype) complete factorial design. Sorghum grown under reduced UV were 23% taller and had 22% fewer leaves. Among genotypes, the WT plants were 5%–12% taller than the bmr6, bmr12 and dm mutants. The near‐ambient UV‐B treatment group was more effective at UV screening and had a 16% higher UV‐screening effectiveness than those under reduced UV‐B. Sorghum plants with the bmr6 and dm genotypes had 8%–19% higher UV‐shield than the bmr12 and WT. Plants grown under the reduced UV‐B treatment had 5% less hemicellulose and 6% more cellulose in their cell walls. There were no overall treatment effects on bulk soluble phenolics, chlorophyll fluorescence (Fv/Fm) or lignin concentrations. These results are a possible indication that the bmr mutants of S. bicolor have a varied response to UV‐B exclusion due to alterations in the phenylpropanoid pathway leading to redistribution of metabolites.

Deciphering High-Temperature-Induced Lignin Biosynthesis in Wheat through Comprehensive Transcriptome Analysis.

This study systematically investigated the physiological and molecular responses of the wheat mutant 'XC-MU201' under high-temperature stress through comprehensive transcriptome analysis and physiological measurements. RNA sequencing of 21 samples across seven different treatment groups revealed, through Weighted Gene Co-expression Network Analysis (WGCNA), 13 modules among 9071 genes closely related to high-temperature treatments. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed significant enrichment of lignin biosynthesis-related modules under high-temperature conditions, especially at the H-10DAT, H-20DAT, and H-30DAT time points. Experimental results demonstrated a significant increase in lignin content in high-temperature-treated samples, confirmed by tissue staining methods, indicating wheat's adaptation to heat damage through lignin accumulation. The phenylalanine ammonia-lyase gene (TaPAL33) was significantly upregulated under high-temperature stress, peaking at H-30DAT, suggesting its critical role in cellular defense mechanisms. Overexpression of TaPAL33 in the wheat variety 'Xinchun 11' enhanced lignin synthesis but inhibited growth. Subcellular localization of GFP-labeled TaPAL33 in tobacco cells showed its distribution mainly in the cytoplasm and cell membrane. Transgenic wheat exhibited higher PAL enzyme activity, enhanced antioxidant defense, and reduced oxidative damage under high-temperature stress, outperforming wild-type wheat. These results highlight TaPAL33's key role in improving wheat heat tolerance and provide a genetic foundation for future research and applications.