Immunocytochemical Localization of Enzymes Involved in Lignification of the Cell Wall

O -methyltransferase, and cinnnamyl alcohol dehydrogenase were localized to differentiating xylem. These enzymes are particularly abundant during secondary wall formation. Immunolabeling was observed on polysomes and in the cytosol of the cells during secondary wall formation, indicating that these enzymes are synthesized in the polysomes and released in the cytosol. The synthesis of monolignols might occur in the cytosol. Immunolabeling of anionic peroxidase was also localized to the differentiating xylem, particularly during secondary wall formation. The labeling, however, was observed in the rough endoplasmic reticulum (r-ER), the Golgi apparatus, and the plasma membrane, indicating that peroxidase is synthesized in the r-ER, transported to the Golgi apparatus, and localized on the plasma membrane by fusion of the Golgi vesicles to the membrane. Received 3 September 2001/ Accepted in revised form 16 October 2001     

禾本科植物细胞壁的木质化和阿魏酰化

介绍了禾本科植物细胞壁木质化和阿魏酰化的过程及其生理意义,并阐述了木质化和阿魏酰化在细胞壁分子网络形成过程中的作用。     

亚硫酸钠处理对与采后竹笋木质化作用有关的细胞壁物质及酶活性的影响

研究了Na2SO3处理对与采后竹笋木质化作用相关的细胞壁物质及其酶活性的影响.结果表明1%Na2SO3处理能显著延缓竹笋组织中多聚半乳糖醛酸酶活性的降低和抑制苯丙氨酸解氨酶活性的上升,因此水溶性果胶含量显著高于对照,硬度、木质素和原果胶含量显著低于对照.但1%Na2SO3处理对纤维素酶、果胶甲酯酶活性和纤维素含量无显著影响.     

Cell Wall Free Space of Cucumis Hypocotyls Contains NAD and a Blue Light-Regulated Peroxidase Activity

Solutions were obtained from the cell wall free space of red light-grown cucumber (Cucumis sativus L.) hypocotyl sections by a low-speed centrifugation technique. The centrifugate contained NAD and peroxidase but no detectable cytoplasmic contamination, as indicated by the absence of the activity of glucose-6-phosphate dehydrogenase from the cell wall solution. Peroxidase activity centrifuged from the cell wall of red light-grown cucumber hypocotyl section could be resolved into at least three cathodic isoforms and two anodic isoforms by isoelectric focusing. Treatment of red light-grown cucumber seedlings with a 10-minute pulse of high-intensity blue light increased the level of cell wall peroxidase by about 60% and caused a qualitative change in the anodic isoforms of this enzyme. The increase in peroxidase activity was detectable within 25 minutes after the start of the blue light pulse, was maximal at 35 minutes, and declined to control levels by 45 minutes of irradiation. The inhibitory effect of blue light on hypocotyl elongation was more rapid than the effect of blue light on total wall peroxidase activity, leading to the conclusion that growth and peroxidase activity are not causally related.     

Changes in Cell Wall Architecture of Differentiating Tracheids of Pinus thunbergii during Lignification

The cell wall architecture, before and after lignification,of differentiating tracheids in Pinus thunbergii has been examinedusing a rapid-freeze deep-etching technique combined with transmissionelectron microscopy. Replicas of cells from the cambial zoneshowed that the unlignified primary cell wall was highly porouswith microfibrils extensively interconnected by crosslinks.The unlignified secondary cell wall has unidirectional microfibrils,more or less associated in bundles, forming a wavy pattern aroundpores of characteristic slit-like shape with narrowing ends.As the lignification progresses, the cell wall structure becomesdense, with no detectable pores. Delignification of wood samplesleads to the reappearance of crosslinks, individual microfibrilsand pores in the secondary cell wall, although in a somewhataltered shape. In addition, cellulose-synthesizing enzyme complexes(rosettes) have for the first time been detected on the plasmamembrane of differentiating xylem cells of softwood. (Received August 28, 1998; Accepted March 10, 1999)     

Aspergillus Enzymes Involved in Degradation of Plant Cell Wall Polysaccharides

Degradation of plant cell wall polysaccharides is of major importance in the food and feed, beverage, textile, and paper and pulp industries, as well as in several other industrial production processes. Enzymatic degradation of these polymers has received attention for many years and is becoming a more and more attractive alternative to chemical and mechanical processes. Over the past 15 years, much progress has been made in elucidating the structural characteristics of these polysaccharides and in characterizing the enzymes involved in their degradation and the genes of biotechnologically relevant microorganisms encoding these enzymes. The members of the fungal genus Aspergillus are commonly used for the production of polysaccharide-degrading enzymes. This genus produces a wide spectrum of cell wall-degrading enzymes, allowing not only complete degradation of the polysaccharides but also tailored modifications by using specific enzymes purified from these fungi. This review summarizes our current knowledge of the cell wall polysaccharide-degrading enzymes from aspergilli and the genes by which they are encoded.     

pH-Dependent Interactions between Pea Cell Wall Polymers Possibly Involved in Wall Deposition and Growth

In an effort to detect a pH-dependent release of polymers such as xyloglucans, thought to be involved in auxin-induced cell wall expansion during growth, radioactively labeled cell walls from pea stem tissue were incubated at different pH values, and changes in water-soluble, ethanol- or trichloroacetic acid-insoluble components were determined. This revealed the occurrence, at neutral pH, of a time- and pH-dependent binding of soluble pectin, in the walls, to a heat-labile, presumably protein, wall component, yielding a trichloroacetic acid-insoluble pectin-protein complex. This reaction, which can also be observed between polymers in water extracts of cell walls, is inhibited at low pH and by Ca²⁺, and appears to be of a physical, possibly lectin-like, nature. Progressive binding of pectin or of the pectin-protein complex to the insoluble wall structure is also observed. These reactions may be involved in wall assembly during its deposition, and may participate in, or be analogous to pH-dependent physical interactions that participate in, wall extension during cell growth.     

Benzothiazinones Mediate Killing of Corynebacterineae by Blocking Decaprenyl Phosphate Recycling Involved in Cell Wall Biosynthesis

Benzothiazinones (BTZs) are a new class of sulfur containing heterocyclic compounds that target DprE1, an oxidoreductase involved in the epimerization of decaprenyl-phosphoribose (DPR) to decaprenyl-phosphoarabinose (DPA) in the Corynebacterineae, such as Corynebacterium glutamicum and Mycobacterium tuberculosis. As a result, BTZ inhibition leads to inhibition of cell wall arabinan biosynthesis. Previous studies have demonstrated the essentiality of dprE1. In contrast, Cg-UbiA a ribosyltransferase, which catalyzes the first step of DPR biosynthesis prior to DprE1, when genetically disrupted, produced a viable mutant, suggesting that although BTZ biochemically targets DprE1, killing also occurs through chemical synthetic lethality, presumably through the lack of decaprenyl phosphate recycling. To test this hypothesis, a derivative of BTZ, BTZ043, was examined in detail against C. glutamicum and C. glutamicum::ubiA. The wild type strain was sensitive to BTZ043; however, C. glutamicum::ubiA was found to be resistant, despite possessing a functional DprE1. When the gene encoding C. glutamicum Z-decaprenyl-diphosphate synthase (NCgl2203) was overexpressed in wild type C. glutamicum, resistance to BTZ043 was further increased. This data demonstrates that in the presence of BTZ, the bacilli accumulate DPR and fail to recycle decaprenyl phosphate, which results in the depletion of decaprenyl phosphate and ultimately leads to cell death.     

Role of Peroxidase in Lignification of Tobacco Cells : II. Regulation by Phenolic Compounds

Coniferyl alcohol is the primary substrate for peroxidase-mediated lignification, a process which depends on the generation of H₂O₂ by NADH oxidation. We measured the concentrations of various phenols (synthetic and natural) at which maximal enhancement of NADH oxidation occurs. Coniferyl alcohol was found to stimulate NADH oxidation at a much lower concentration (0.01 mm) than other natural or synthetic phenols (1-100 mm). In addition, coniferyl alcohol prevented the conversion of active peroxidase into the inactive intermediate compound III—which is usually formed in the presence of NADH—at equally low concentrations. This conversion was found to be a prerequisite for stimulation of NADH-oxidation, but it was not necessarily connected to stimulation.     

Preinoculation with Tobacco Necrosis Virus Enhances Peroxidase Activity and Lignification in Cucumber, as a Resistance Response to Sphaerotheca fuliginea

Abstract Cucumber plants were mechanically inoculated with TNV and challenge-inoculated after 7 days with Sphaerotheca fuliginea. The development of the fungus was followed by light microscopy and the modifications of the host leaf cells were studied by histochemical and cytochemical reactions. Conidial germination was similar in control and TNV-infected plants, and in the following 2 or 3 days S. fuliginea development was also similar. Thereafter in control plants S. fuliginea development progressed steadily and no modifications appeared in the leaf host cells, while in TNV-infected plants strongly autofluorescing papillae were formed, and peroxidase activity was detected in the walls of many epidermal cells of the challenge-inoculated, leaf. Lignification ensued, and fungal growth was strongly inhibited. Protection was obtained provided the number of necrotic lesions was at least 12 per cotyledon, and was elicited even if the TNV-infected leaf was removed 7 days after infection, before challenge inoculation. No protection was induced when the TNV-infected leaf was removed 3 days after infection.     

Homologues of the Bacillus subtilis SpoVB Protein Are Involved in Cell Wall Metabolism

Members of the COG2244 protein family are integral membrane proteins involved in synthesis of a variety of extracellular polymers. In several cases, these proteins have been suggested to move lipid-linked oligomers across the membrane or, in the case of Escherichia coli MviN, to flip the lipid II peptidoglycan precursor. Bacillus subtilis SpoVB was the first member of this family implicated in peptidoglycan synthesis and is required for spore cortex polymerization. Three other COG2244 members with high similarity to SpoVB are encoded within the B. subtilis genome. Mutant strains lacking any or all of these genes (yabM, ykvU, and ytgP) in addition to spoVB are viable and produce apparently normal peptidoglycan, indicating that their function is not essential in B. subtilis. Phenotypic changes associated with loss of two of these genes suggest that they function in peptidoglycan synthesis. Mutants lacking YtgP produce long cells and chains of cells, suggesting a role in cell division. Mutants lacking YabM exhibit sensitivity to moenomycin, an antibiotic that blocks peptidoglycan polymerization by class A penicillin-binding proteins. This result suggests that YabM may function in a previously observed alternate pathway for peptidoglycan strand synthesis.The Bacillus subtilis spoVB gene was first identified as a locus in which a mutation could produce a block at a late stage of spore development (14, 30). Analysis of this locus revealed that it encoded an apparent integral membrane protein (33), and a detailed analysis of a spoVB null mutant demonstrated a block at a very early step in synthesis of the spore cortex peptidoglycan (PG) (40). The mutant synthesized essentially no cortex and accumulated cytoplasmic PG precursors, the same phenotype found in other mutant strains blocked in functions known to be directly involved in PG polymerization (40). These results suggested that SpoVB plays a direct role in assembly or function of the spore PG synthesis apparatus.PG synthesis is a highly conserved and complex process that must span the cell membrane (reviewed in reference 38). Soluble nucleotide-linked PG precursors are synthesized in the cytoplasm. N-Acetylmuramic acid with a pentapeptide side chain is then transferred to an undecaprenol lipid carrier to produce lipid I, with subsequent addition of N-acetylglucosamine to produce lipid II, undecaprenyl-pyrophosphoryl-N-acetylmuramic acid (pentapeptide)-N-acetylglucosamine. Lipid II is then flipped across the membrane via an unknown mechanism. Two families of proteins have been postulated to perform this function: the SEDS family of integral membrane proteins, including FtsW, RodA, and SpoVE (13), and, more recently, the COG2244 family (23), which includes SpoVB and the MviN (MurJ) protein of Escherichia coli (35). In both cases, loss of a protein within one of these families has been shown to result in a block in PG synthesis and the accumulation of lipid-linked and/or soluble PG precursors (16, 20, 35, 40).In the standard model of PG synthesis, flippase activity brings the disaccharide-pentapeptide moieties to the penicillin-binding proteins (PBPs), which polymerize the PG macromolecule on the outer surface of the membrane (39). The class A, high-molecular-weight PBPs possess an N-terminal glycosyl transferase domain that polymerizes the disaccharides into polysaccharide chains (38). These chains are cross-linked via the transpeptidase activity within the penicillin-binding, C-terminal domains of both the class A and the class B PBPs. The N-terminal domains of the class A PBPs and the closely related monofunctional glycosyl transferases found in some species are the only defined PG glycan strand polymerases, and in several species the presence of at least one of these enzymes is essential. However, in B. subtilis (26) and Enterococcus faecalis (3), strains lacking all of these known glycosyl transferases are viable and produce PG walls, indicating the presence of another glycosyl transferase capable of this activity. This alternate glycosyl transferase is distinct in that it is relatively resistant to moenomycin (3, 26), an inhibitor of the class A PBP glycosyl transferase activity (6).Given the strong and early block in cortex PG polymerization observed to occur in a spoVB mutant (40), we wished to further analyze the potential role of this class of protein. SpoVB is a member of a relatively large family of proteins, COG2244 (23), some of which are involved in polymerization of other polysaccharides in bacteria, archaea, and eukaryotes. Bioinformatic analysis has generally predicted that these proteins span the membrane 12 to 14 times, and in some cases experimental evidence has supported this structure (7, 24). A role generally ascribed to these proteins is the flipping of lipid-linked oligosaccharides, produced on the inner face of a membrane, to the outside, where the oligosaccharides are then further polymerized or transferred to other substrates. Some prominent members of this family include Wzx, which functions in O-antigen synthesis in gram-negative bacteria (41); TuaB, which functions in teichuronic acid synthesis in B. subtilis (36); and Rft1, which functions in protein glycosylation in eukaryotes (12). MviN is essential in some gram-negative species, including Burkholderia pseudomallei, E. coli, and Sinorhizobium meliloti (22, 34), and has been shown to play a role in E. coli PG synthesis (16, 35). A Rhizobium tropici mutation that truncates mviN approximately 50% into the coding sequence was not lethal (29). However, it is not known whether this was the sole mviN homolog in the genome or whether the truncated gene product might be functional.We have analyzed the phenotypic properties of B. subtilis strains lacking other proteins within the COG2244 family that are most closely related to SpoVB. Results suggest that these proteins also play roles in PG synthesis and that, in one case, this role is in a synthetic system that is relatively moenomycin resistant. We postulate that these proteins function in an alternate pathway for PG synthesis that may involve the flipping of lipid-linked PG oligosaccharides rather than lipid II disaccharides.     

Cytochemical Detection of Cell Wall Bound Peroxidase in Rust Infected Broad Bean Leaves*

Cell wall bound peroxidase activity, cytochemically detected by 3,3-diaminobenzidine (DAB), appears unevenly distributed in areolae of broad bean (cv. Aguadulce) leaves infected by the rust fungus Uromyces viciae-fahae (Pers.) Schroet. DAB positivity is not significantly traceable at the periphery of the areola and close to the site of uredinium formation; heavy DAB deposits occur on walls of haustoria containing mesophyll cells. Induction of localized peroxidase activity appears strictly related to the haustorium mother cell differentiation, i.e. to the incipient parasitic phase; it does not, however, counteract the intracellular growth of the haustorium.     

An Accounting of Horseradish Peroxidase Isozymes Associated with the Cell Wall and Evidence that Peroxidase Does Not Contain Hydroxyproline

Isopycnic equilibrium centrifugation techniques were used to determine whether any horseradish (Amoracia lapathifolia) peroxidase isozymes were associated with hydroxyproline containing moieties. Purified peroxidase, horseradish root extracts, and peroxidase isozymes released from horseradish root cell walls were tested. In no case could any peak of peroxidase activity be found to band with hydroxyproline.     

Distribution of Yeast Cell Wall Lytic Activity among Microorganisms

An α-glucosidase has been isolated from the mycelia of Penicillium purpurogenum in electrophoretically homogeneous form, and its properties have been investigated. The enzyme had a molecular weight of 120,000 and an isoelectric point of pH 3.2. The enzyme had a pH optimum at 3.0 to 5.0 with maltose as substrate. The enzyme hydrolyzed not only maltose but also amylose, amylopectin, glycogen, and soluble starch, and glucose was the sole product from these substrates. The Km value for maltose was 6.94×10^?4 m. The enzyme hydrolyzed phenyl α-maltoside to glucose and phenyl α-glucoside. The enzyme had α-glucosyltransferase activity, the main transfer product from maltose being maltotriose. The enzyme also catalyzed the transfer of α-glucosyl residue from maltose to riboflavin.     

Control of Cell pH in the T84 Colon Cell Line

Cell pH regulation was investigated in the T84 cell line derived from epithelial colon cancer. Cell pH was measured by ratiometric fluorescence microscopy using the fluorescent probe BCECF. Basal pH was 7.17 ± 0.023 (n= 48) in HEPES Ringer. After acidification by an ammonium pulse, cell pH recovered toward normal at a rate of 0.13 ± 0.011 pH units/min in the presence of Na⁺, but in the absence of this ion or after treatment with 0.1 mm hexamethylene amiloride (HMA) no significant recovery was observed, indicating absence of Na⁺ independent H⁺ transport mechanisms in HEPES Ringer. In CO₂/HCO⁻ ₃ Ringer, basal cell pH was 7.21 ± 0.020 (n= 35). Changing to HEPES Ringer, a marked alkalinization was observed due to loss of CO₂, followed by return to the initial pH at a rate of −0.14 ± 0.012 (n= 8) pH/min; this return was retarded or abolished in the absence of Cl⁻ or after addition of 0.2 mm DIDS, suggesting extrusion of bicarbonate by Cl⁻/HCO⁻ ₃ exchange. This exchange was not Na⁺ dependent. When Na⁺ was added to cells incubated in 0 Na⁺ Ringer while blocking Na⁺/H⁺ exchange by HMA, cell alkalinization by 0.19 ± 0.04 (n= 11) pH units was observed, suggesting the presence of Na⁺/HCO⁻ ₃ cotransport carrying HCO⁻ ₃ into these cells, which was abolished by DIDS. These experiments, thus, show that Na⁺/H⁺ and Cl⁻/HCO⁻ ₃ exchange and Na⁺/HCO⁻ ₃ cotransport participate in cell pH regulation in T84 cells. Received: 3 April 2000/Revised: 22 June 2000     

Measuring Plant Cell Wall Extension (Creep) Induced by Acidic pH and by Alpha-Expansin

Growing plant cell walls characteristically exhibit a property known as ''acid growth'', by which we mean they are more extensible at low pH (< 5) ¹. The plant hormone auxin rapidly stimulates cell elongation in young stems and similar tissues at least in part by an acid-growth mechanism ^{2, 3}. Auxin activates a H⁺ pump in the plasma membrane, causing acidification of the cell wall solution. Wall acidification activates expansins, which are endogenous cell wall-loosening proteins ⁴, causing the cell wall to yield to the wall tensions created by cell turgor pressure. As a result, the cell begins to enlarge rapidly. This ''acid growth'' phenomenon is readily measured in isolated (nonliving) cell wall specimens. The ability of cell walls to undergo acid-induced extension is not simply the result of the structural arrangement of the cell wall polysaccharides (e.g. pectins), but depends on the activity of expansins ⁵. Expansins do not have any known enzymatic activity and the only way to assay for expansin activity is to measure their induction of cell wall extension. This video report details the sources and preparation techniques for obtaining suitable wall materials for expansin assays and goes on to show acid-induced extension and expansin-induced extension of wall samples prepared from growing cucumber hypocotyls.To obtain suitable cell wall samples, cucumber seedlings are grown in the dark, the hypocotyls are cut and frozen at -80 °C. Frozen hypocotyls are abraded, flattened, and then clamped at constant tension in a special cuvette for extensometer measurements. To measure acid-induced extension, the walls are initially buffered at neutral pH, resulting in low activity of expansins that are components of the native cell walls. Upon buffer exchange to acidic pH, expansins are activated and the cell walls extend rapidly. We also demonstrate expansin activity in a reconstitution assay. For this part, we use a brief heat treatment to denature the native expansins in the cell wall samples. These inactivated cell walls do not extend even in acidic buffer, but addition of expansins to the cell walls rapidly restores their ability to extend.Open in a separate windowClick here to view.^{(58M, flv)}     

Remote Control of Intestinal Stem Cell Activity by Haemocytes in Drosophila

The JAK/STAT pathway is a key signaling pathway in the regulation of development and immunity in metazoans. In contrast to the multiple combinatorial JAK/STAT pathways in mammals, only one canonical JAK/STAT pathway exists in Drosophila. It is activated by three secreted proteins of the Unpaired family (Upd): Upd1, Upd2 and Upd3. Although many studies have established a link between JAK/STAT activation and tissue damage, the mode of activation and the precise function of this pathway in the Drosophila systemic immune response remain unclear. In this study, we used mutations in upd2 and upd3 to investigate the role of the JAK/STAT pathway in the systemic immune response. Our study shows that haemocytes express the three upd genes and that injury markedly induces the expression of upd3 by the JNK pathway in haemocytes, which in turn activates the JAK/STAT pathway in the fat body and the gut. Surprisingly, release of Upd3 from haemocytes upon injury can remotely stimulate stem cell proliferation and the expression of Drosomycin-like genes in the intestine. Our results also suggest that a certain level of intestinal epithelium renewal is required for optimal survival to septic injury. While haemocyte-derived Upd promotes intestinal stem cell activation and survival upon septic injury, haemocytes are dispensable for epithelium renewal upon oral bacterial infection. Our study also indicates that intestinal epithelium renewal is sensitive to insults from both the lumen and the haemocoel. It also reveals that release of Upds by haemocytes coordinates the wound-healing program in multiple tissues, including the gut, an organ whose integrity is critical to fly survival.     

辐射诱导小鼠淋巴瘤细胞凋亡涉及NADPH氧化酶的活性

用60Coγ射线对小鼠淋巴瘤细胞3SB(p53 / )和1B1C4(p53-/-)进行照射处理。观察了辐射后细胞形态学变化,结果发现,3SB对γ射线诱导的凋亡非常敏感,而1B1C4细胞对辐射具有抗性。DNA片断化试验和藻红B染色试验的结果也证实这一点。进一步分析了凋亡信号途径上的caspase-3和p53。在3SB细胞中,检测到激活的caspase-3并发现p53的表达随辐射剂量的增加而增高。比较了两种细胞中caspase-3mRNA的表达,但未见差异。对两种细胞中的NADPH氧化酶活性的测定结果表明,凋亡的3SB细胞中的NADPH氧化酶活性增高。因此,在电离辐射诱导细胞凋亡的过程中,NADPH氧化酶参与了上游信号的转导。     

Label-free in situ Imaging of Lignification in Plant Cell Walls

Meeting growing energy demands safely and efficiently is a pressing global challenge. Therefore, research into biofuels production that seeks to find cost-effective and sustainable solutions has become a topical and critical task. Lignocellulosic biomass is poised to become the primary source of biomass for the conversion to liquid biofuels^1-6. However, the recalcitrance of these plant cell wall materials to cost-effective and efficient degradation presents a major impediment for their use in the production of biofuels and chemicals⁴. In particular, lignin, a complex and irregular poly-phenylpropanoid heteropolymer, becomes problematic to the postharvest deconstruction of lignocellulosic biomass. For example in biomass conversion for biofuels, it inhibits saccharification in processes aimed at producing simple sugars for fermentation⁷. The effective use of plant biomass for industrial purposes is in fact largely dependent on the extent to which the plant cell wall is lignified. The removal of lignin is a costly and limiting factor⁸ and lignin has therefore become a key plant breeding and genetic engineering target in order to improve cell wall conversion.Analytical tools that permit the accurate rapid characterization of lignification of plant cell walls become increasingly important for evaluating a large number of breeding populations. Extractive procedures for the isolation of native components such as lignin are inevitably destructive, bringing about significant chemical and structural modifications^9-11. Analytical chemical in situ methods are thus invaluable tools for the compositional and structural characterization of lignocellulosic materials. Raman microscopy is a technique that relies on inelastic or Raman scattering of monochromatic light, like that from a laser, where the shift in energy of the laser photons is related to molecular vibrations and presents an intrinsic label-free molecular "fingerprint" of the sample. Raman microscopy can afford non-destructive and comparatively inexpensive measurements with minimal sample preparation, giving insights into chemical composition and molecular structure in a close to native state. Chemical imaging by confocal Raman microscopy has been previously used for the visualization of the spatial distribution of cellulose and lignin in wood cell walls^12-14. Based on these earlier results, we have recently adopted this method to compare lignification in wild type and lignin-deficient transgenic Populus trichocarpa (black cottonwood) stem wood¹⁵. Analyzing the lignin Raman bands^16,17 in the spectral region between 1,600 and 1,700 cm^-1, lignin signal intensity and localization were mapped in situ. Our approach visualized differences in lignin content, localization, and chemical composition. Most recently, we demonstrated Raman imaging of cell wall polymers in Arabidopsis thaliana with lateral resolution that is sub-μm¹⁸. Here, this method is presented affording visualization of lignin in plant cell walls and comparison of lignification in different tissues, samples or species without staining or labeling of the tissues.Download video file.^{(47M, mov)}