Search Results (67)

Powdery mildew in wheat, caused by the biotrophic fungus Blumeria graminis f. sp. tritici (Bgt), is a major threat to global wheat production, yet the molecular mechanisms underlying differential cultivar resistance remain largely unresolved. In this study, tandem mass tag (TMT)-based quantitative proteomics was employed to investigate protein dynamics in resistant (Yannong37) and susceptible (Yannong1766) wheat cultivars at 0 and 24 h following Bgt inoculation. A total of 276 proteins exhibited significant changes in abundance after infection, with enrichment in cell wall and plasmodesmata-associated proteins. Comparative analysis further identified 456 differentially expressed proteins between the two cultivars at 24 h post-inoculation. Protein–protein interaction network analysis indicated that proteins involved in secondary metabolism and immune responses form coordinated regulatory networks contributing to disease resistance. RT–qPCR validation supported the reliability of the proteomic data. Notably, TaCAD-A1 displayed higher transcript abundance in the resistant cultivar and was associated with reduced fungal biomass accumulation. Silencing of TaCAD-A1 resulted in decreased expression of multiple defense-related genes. Collectively, these findings suggest that TaCAD-A1 may positively contribute to wheat resistance against Bgt infection and may be associated with defense responses and monolignol biosynthesis-related processes. Full article

The existence of lignin in Physcomitrium patens has been controversial. However, cinnamyl alcohol dehydrogenase (CAD), the key enzyme in monolignol biosynthesis, has been identified with four gene members in P. patens. Despite the roles of PpCAD1 in moss architecture being proven in a previous study, the functions and molecular mechanisms of PpCAD4 remain largely unexplored in early terrestrial plants. This study aims to unravel this mystery via a comprehensive analysis of the transcriptome and metabolome of PpCAD4-overexpression (OE) lines compared with wild type (WT) under Botrytis cinerea treatment, firstly. A total of 475 and 1368 significantly differentially expressed genes in PpCAD4-OE lines compared to the wild type at 6 h and 12 h post-inoculation, which were predominantly enriched in pathways involving flavonoid, phenylpropanoid biosynthesis, and plant hormone signal transduction. Concurrently, metabolomic profiling revealed 160 and 114 differentially accumulated metabolites in PpCAD4-OE at the corresponding time points, with phenolic acids and flavonoids collectively constituting over 45% of these compounds. Furthermore, the MADS-box transcriptional factor PpMC6 negatively regulated PpCAD4 expression by yeast-one-hybrid and dual-luciferase assays. Finally, Catalase isozyme 2 (PpCAT2) and E3 ubiquitin-protein ligase (PpE3) were identified as interactive partners with PpCAD4, respectively, deducing that the increasing of reactive oxygen species might be promoted by PpCAT2 degradation through PpE3 after B. cinerea assault. Our results demonstrated that the essential roles and potential mechanisms of PpCAD4 are essential for defense against pathogens during the adaptation to land in moss. Full article

This study focuses on obtaining lignin-based hydrogels from pruning residues of orange trees in the Safor region (Valencia) using an alkaline extraction method. The structural analysis of the obtained lignin was carried out using Fourier-transform infrared spectroscopy (FTIR), which revealed the characteristic functional groups of lignin, as well as its structural monolignols: syringyl and guaiacyl. The thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. The DSC thermogram revealed a relatively low glass transition temperature (T_g) of 67 °C, which may be attributed to partial lignin chain degradation during alkaline extraction. Soda lignin was obtained at 190 °C with an approximate yield of 10.8% relative to the initial biomass and subsequently used to synthesize poly(vinyl alcohol) (PVA)-based hydrogels for ibuprofen encapsulation. Finally, the release experiments of the encapsulated ibuprofen were carried out in an aqueous phosphate buffer medium (pH = 7) at room temperature. A multi-curve response analysis (MCR) algorithm using the Korsmeyer–Peppas (KP) concentration model was used to analyze the release curves, which concluded that the drug and water-soluble lignin fraction (SLF) were released at different rates. For both components, a good correlation was obtained between the measured responses and those provided by the KP model. The release profile indicated that approximately 87% of the initial ibuprofen load was released from the hydrogel within 5 h, highlighting the promising potential of lignin-based hydrogels for drug delivery applications. Full article

Lignin is a complex aromatic polymer that constitutes a major fraction of plant biomass and represents a valuable renewable carbon resource. Naturally decaying wood serves as an environmental reservoir of microorganisms capable of degrading lignin. In this study, we isolated and characterized sixteen bacterial strains from decaying Tilia cordata wood using an enrichment culture technique with lignin as the sole carbon source. Taxonomic identification via 16S rRNA gene sequencing revealed microbial diversity spanning the genera Bacillus, Pseudomonas, Stenotrophomonas, and several members of the Enterobacteriaceae family, including Raoultella terrigena isolates. Metagenomic sequencing of the wood substrate revealed an exceptionally rich and balanced bacterial community (Shannon index H′ = 5.07), dominated by Streptomyces, Bradyrhizobium, Bacillus, and Pseudomonas, likely reflecting a specialized consortium adapted to lignin rich late-stage decay. Functional phenotyping demonstrated that all isolates possess ligninolytic potential, evidenced by peroxidase/laccase-type activity through methylene blue decolorization. Dynamic Light Scattering (DLS) and HPLC analyses showed that some isolates, such as Raoultella terrigena MGMM806, effectively depolymerized lignosulfonate into low molecular weight fragments (1.23 nm), while others accumulated intermediate metabolites or completely mineralized the substrate. Growth profiling on monolignol substrates revealed a broad spectrum of catabolic specialization in lignin monomer degradation. The results demonstrate a complex system of metabolic partitioning within a natural bacterial consortium. This collection represents a foundational genetic resource for developing engineered biocatalysts and synthetic microbial communities aimed at the efficient conversion of lignin into valuable aromatic compounds. Full article

Sorghum is a versatile crop that serves as a major source of food, feed, fodder and biofuel globally. Lignin content in sorghum affects multiple important traits, including lodging resistance, forage digestibility and the efficiency of bioenergy production. However, the genetic regulation of lignin content in sorghum remains poorly understood. In this study, we combined transcriptomic and comparative genomic approaches to uncover the genetic network underlying lignin biosynthesis in sorghum. Through comparative genomic analysis, we identified 104 candidate genes involved in lignin biosynthesis. Transcriptome analysis of four sorghum accessions with contrasting lignin contents identified 6132 differentially expressed genes with an enrichment of genes related to phenylpropanoid biosynthesis and cell wall biogenesis. The 104 lignin biosynthesis candidates were significantly enriched (p-value < 0.01) in these differentially expressed genes, with most differentially expressed candidate genes related to monolignol biosynthesis and polymerization being up-regulated in high-lignin accessions. These up-regulated genes are related to all key enzymes involved in lignin biosynthesis, suggesting that the elevated lignin content in these accessions results from a collective increase in enzyme activity. Sequence analysis revealed a significant reduction in genetic diversity across lignin biosynthesis genes in cultivated sorghum compared to wild sorghum. Moreover, selection signals during domestication were identified in 30 lignin biosynthesis genes, 22 of which were differentially expressed, further supporting the functional relevance of these differentially expressed genes in lignin biosynthesis. Overall, our findings uncover the lignin biosynthesis gene network in sorghum and offer potential targets for future functional studies and trait manipulation. Full article

Zinc (Zn) is an essential micronutrient required for plants to perform various metabolic functions, and plant responses to Zn deficiency have been extensively studied. However, excessive levels of Zn in soil can induce toxic effects in plants, posing a substantial challenge to global agricultural productivity. Consequently, elucidating the response mechanisms of crop plants to excessive Zn toxicity is currently of great significance. In this study, seedlings of maize inbred line B73 were exposed to excessive Zn treatment, and transcriptomic profiling of the roots was conducted at 0, 2, 6, 12, 24, and 48 h post-treatment. In addition to changes in the expression of genes encoding zinc-regulated, iron-regulated transporter-like protein (ZIP), metal tolerance protein (MTP), and yellow stripe-like (YSL) transporter family members involved in Zn transport, we observed that differentially expressed genes (DEGs) were significantly enriched in the phenylpropanoid–lignin metabolic pathway across all treatment stages, including the early (2 and 6 h), middle (12 and 24 h), and late (48 h) stages of Zn treatment. Among the 11 core structural enzyme-encoding genes involved in monolignols biosynthesis from phenylalanine in this pathway, the expression of eight of them was altered by Zn treatment. Additionally, genes encoding peroxidase (POD), which are responsible for the polymerization of monolignols into lignin, demonstrated extensive changes across all treatment stages, particularly at the late stage. The expression levels of these key enzyme genes were further validated using quantitative real-time PCR. Correspondingly, the activity of POD enzymes and the lignin content both significantly increased in Zn treated roots. These findings suggest that the phenylpropanoid–lignin metabolic pathway plays a crucial role in maize root responses to excessive Zn stress. Full article

The jasmonic acid (JA) signaling pathway has been demonstrated to play a crucial role in plant defense against herbivorous insects. However, the relationship between Ectropis obliqua-induced defensive metabolites and the JA signaling pathway in tea plants remains poorly understood. In this study, we investigated seven key special metabolites, including p-coumaroylputrescine, feruloylputrescine, prunin, naringenin, and three monolignols, to address this knowledge gap. Epicatechin was selected as a positive control based on its well-documented regulation through the JA signaling pathway. Notably, the content of all selected compounds was significantly increased by E. obliqua infestation. Furthermore, exogenous application of high-dose methyl jasmonate (MeJA) induced the accumulation of six of the eight compounds, excluding p-coumaryl alcohol and sinapyl alcohol, whereas low-dose MeJA failed to elicit their accumulation. To confirm the results, we screened two bioactive molecules, D-allose and L-theanine, which significantly increased the endogenous JA levels at low concentrations. Interestingly, neither D-allose nor L-theanine triggered the biosynthesis of these defensive compounds. Additionally, D-allose-treated tea leaves had no significant effect on the performance of E. obliqua larvae. These findings demonstrate that the metabolic accumulation induced by E. obliqua is mediated through a high-threshold JA signaling cascade. This study provides novel insights into the relationship between plant resistance and JA signaling pathway, advancing our understanding of special metabolites mediated plant-insect interactions. Full article

Phytoalexins are specialized metabolites that are synthesized by plants in response to pathogens. A paradigm in transcription factor (TF) biology is that conserved TFs have dedicated roles across plant lineages in regulating specific branches of specialized metabolism. However, the Arabidopsis (Arabidopsis thaliana) NAC family TF ANAC042 (a.k.a. JUNGBRUNNEN1 or JUB1) regulates the synthesis of camalexin, a Trp-derived phytoalexin specifically produced by several Brassicaceae species, whereas its homolog in soybean (Glycine max) regulates the synthesis of glyceollins, which are Phe-derived phytoalexins specific to soybean. The question addressed by this research is whether ANAC042 broadly regulates phytoalexin biosynthetic pathways in Arabidopsis. Using a novel matrix-assisted laser desorption ionization high-resolution mass spectrometry (MALDI-HRMS) method, we found that the Arabidopsis loss-of-function mutant anac042–1 elicited with bacterial flagellin (Flg22) is deficient in lineage-specific Trp- and conserved Phe-derived phytoalexins—namely camalexin and 4-hydroxyindole-3-carbonyl nitrile (4OH-ICN), and pathogen-inducible monolignols and scopoletin, respectively. Overexpressing ANAC042 in the anac042-1 mutant restored or exceeded wildtype amounts of the metabolites. The expression of phytoalexin biosynthetic genes in mutant and overexpression lines mirrored the accumulation of metabolites. Yeast-one hybrid and promoter-reporter assays in Nicotiana benthamiana found that the ANAC042 protein directly binds and activates the promoters of CYP71B15, CYP71A12, and PAL1 genes for the synthesis of camalexin, 4OH-ICN, and pathogen-inducible monolignol/scopoletin, respectively. Our results demonstrate that ANAC042 regulates conserved and lineage-specific phytoalexin pathways in Arabidopsis. The latter suggests that it is an opportunistic TF that has coopted lineage-specific genes into phytoalexin metabolism, thus providing an exception to the current paradigm. Full article

In conifers, compression wood (CW) with a high lignin content forms at the base of the stem or branch in response to gravity, which is a good model system for studying lignin-rich wood formation. In this study, we identified and characterized the laccase gene family (PdeLAC) in Korean red pine (Pinus densiflora), which is integral to monolignol polymerization. Phylogenetic analysis of 54 PdeLAC genes with those from gymnosperms (i.e., Pinus taeda and Picea abies) and angiosperms (i.e., Populus trichocarpa, Arabidopsis thaliana, and Oryza sativa) revealed their categorization into five groups, highlighting distinct evolutionary relationships compared to angiosperms. Gene structure and motif analysis showed conserved copper-binding loops and variable substrate-binding loops, suggesting functional diversity. Expression profiling indicated that 23 PdeLAC genes, including three (PdeLAC28, PdeLAC1, and PdeLAC31) homologous to AtLAC17, were upregulated in developing xylem during the growing season, particularly in CW. Transgenic poplars overexpressing PdeLAC28 exhibited increased xylem area, cell wall thickness, and Klason lignin content, underscoring its role in lignin biosynthesis and CW formation. This study provides valuable insights into the molecular regulation of lignin biosynthesis in CW of P. densiflora, setting a foundation for advancing our understanding of wood formation mechanisms in gymnosperms. Full article

Mulberry (Morus alba L.) is a significant economic tree species in China. The lignin component serves as a critical limiting factor that impacts both the forage quality and the conversion efficiency of mulberry biomass into biofuel. Cinnamoyl CoA reductase (CCR; EC 1.21.1.44) and cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.95) are the key enzymes that catalyze the final two reductive steps in the biosynthesis of monolignols. In this study, we conducted a comprehensive functional analysis to validate the predominant CCR genes involved in monolignol biosynthesis. In this study, we initially validated the predominant CCR genes implicated in monolignol biosynthesis through an extensive functional analysis. Phylogenetic analysis, tissue-specific expression profiling and enzymatic assays indicated that MaCCR1 is the authentic CCR involved in lignin biosynthesis. Furthermore, the expression level of MaCCR1 exhibited a significant positive correlation with lignin content, and the down-regulation of MaCCR1 via virus-induced gene silencing resulted in altered lignin content in mulberry. The down-regulation of MaCCR1 and MaCAD3/4, both individually and concurrently, exhibited markedly different effects on lignin content and mulberry growth. Specifically, the simultaneous down-regulation of MaCCR1 and MaCAD3/4 significantly altered lignin content in mulberry, resulting in dwarfism of the plants. Conversely, the down-regulation of MaCAD3/4 alone not only decreased lignin content but also led to an increase in biomass. These findings offer compelling evidence elucidating the roles of MaCCRs in mulberry and identify specific target genes, thereby providing a crucial foundation for the genetic modification of lignin biosynthesis. Full article

Monolignols represent pivotal alcohol-based constituents in lignin synthesis, playing indispensable roles in plant growth and development with profound implications for industries reliant on wood and paper. Monolignols and their derivates have multiple applications in several industries. Monolignols exhibit antioxidant activity due to their ability to donate hydrogen atoms or electrons to neutralize free radicals, thus preventing oxidative stress and damage to cells. Characterized by their alcohol functionalities, monolignols present three main forms: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. In nature, particularly in plants, monolignols with geometry (E) predominate over their Z counterparts. The methods for obtaining the three canonical monolignols, two less-common monolignols, and a monolignol analogue are addressed to present an overview of these phenol-based compounds, particularly from a synthetic standpoint. A SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis is used to explain the advantages and disadvantages of synthesizing monolignols, key alcohol-containing raw materials with enormous significance in both plant biology and industrial applications, using bench chemical methods. The uniqueness of this work is that it provides an overview of the synthetic pathways of monolignols to assist researchers in pharmaceutical and biological fields in selecting an appropriate procedure for the preparation of their lignin models. Moreover, we aim to inspire scientists, particularly chemists, to develop more sustainable synthetic protocols for monolignols. Full article

Stems are prone to bending or lodging due to inadequate stem strength, which seriously reduces the cut-flower ornamental quality of herbaceous peony (Paeonia lactiflora Pall.). Plant LACCASE (LAC), a copper-containing polyphenol oxidase, has been shown to participate in the polymerization process of monolignols; however, the role of LAC in regulating the stem strength of P. lactiflora remains unclear. Here, the full-length cDNA of PlLAC15, which demonstrated a positive association with stem strength, was isolated. It consisted of 1790 nucleotides, encoding 565 amino acids that had four typical laccase copper ion-binding domains. Moreover, PlLAC15 was highly expressed in the stem, and its expression level gradually significantly increased during stem development. Furthermore, PlLAC15 was found to be localized specifically to the cell wall, and its recombinant protein exhibited laccase activity. Additionally, the role of PlLAC15 in regulating the stem strength of P. lactiflora was confirmed by transgenic studies. When PlLAC15 was overexpressed in tobacco, stem strength increased by more than 50%, S-lignin was significantly deposited, and the lignification degree of stem xylem fiber cells increased. These results suggested that PlLAC15 facilitated S-lignin deposition to enhance stem strength in P. lactiflora, which would provide precious information that benefits future exploration of stem bending or lodging resistance in plants. Full article

A novel MADS-box transcription factor from Pinus radiata D. Don was characterized. PrMADS11 encodes a protein of 165 amino acids for a MADS-box transcription factor belonging to group II, related to the MIKC protein structure. PrMADS11 was differentially expressed in the stems of pine trees in response to 45° inclination at early times (1 h). Arabidopsis thaliana was stably transformed with a 35S::PrMADS11 construct in an effort to identify the putative targets of PrMADS11. A massive transcriptome analysis revealed 947 differentially expressed genes: 498 genes were up-regulated, and 449 genes were down-regulated due to the over-expression of PrMADS11. The gene ontology analysis highlighted a cell wall remodeling function among the differentially expressed genes, suggesting the active participation of cell wall modification required during the response to vertical stem loss. In addition, the phenylpropanoid pathway was also indicated as a PrMADS11 target, displaying a marked increment in the expression of the genes driven to the biosynthesis of monolignols. The EMSA assays confirmed that PrMADS11 interacts with CArG-box sequences. This TF modulates the gene expression of several molecular pathways, including other TFs, as well as the genes involved in cell wall remodeling. The increment in the lignin content and the genes involved in cell wall dynamics could be an indication of the key role of PrMADS11 in the response to trunk inclination. Full article

Wood is the most important renewable resource not only for numerous practical utilizations but also for mitigating the global climate crisis by sequestering atmospheric carbon dioxide. The compressed wood (CW) of gymnosperms, such as conifers, plays a pivotal role in determining the structure of the tree through the reorientation of stems displaced by environmental forces and is characterized by a high content of lignin. Despite extensive studies on many genes involved in wood formation, the molecular mechanisms underlying seasonal and, particularly, CW formation remain unclear. This study examined the seasonal dynamics of two wood tissue types in Pinus densiflora: CW and opposite wood (OW). RNA sequencing of developing xylem for two consecutive years revealed comprehensive transcriptome changes and unique differences in CW and OW across seasons. During growth periods, such as spring and summer, we identified 2255 transcripts with differential expression in CW, with an upregulation in lignin biosynthesis genes and significant downregulation in stress response genes. Notably, among the laccases critical for monolignol polymerization, PdeLAC17 was found to be specifically expressed in CW, suggesting its vital role in CW formation. PdeERF4, an ERF transcription factor preferentially expressed in CW, seems to regulate PdeLAC17 activity. This research provides an initial insight into the transcriptional regulation of seasonal CW development in P. densiflora, forming a foundation for future studies to enhance our comprehension of wood formation in gymnosperms. Full article

Being an abundant renewable source of aromatic compounds, lignin is an important component of future bio-based economy. Currently, biotechnological processing of lignin through low molecular weight compounds is one of the conceptually promising ways for its valorization. To obtain lignin fragments suitable for further inclusion into microbial metabolism, it is proposed to use a ligninolytic system of white-rot fungi, which mainly comprises laccases and peroxidases. However, laccase and peroxidase genes are almost always represented by many non-allelic copies that form multigene families within the genome of white-rot fungi, and the contributions of exact family members to the overall process of lignin degradation has not yet been determined. In this article, the response of the Trametes hirsuta LE-BIN 072 ligninolytic system to the presence of various monolignol-related phenolic compounds (veratryl alcohol, p-coumaric acid, vanillic acid, and syringic acid) in culture media was monitored at the level of gene transcription and protein secretion. By showing which isozymes contribute to the overall functioning of the ligninolytic system of the T. hirsuta LE-BIN 072, the data obtained in this study will greatly contribute to the possible application of this fungus and its ligninolytic enzymes in lignin depolymerization processes. Full article