Nivolumab plus ipilimumab combination therapy in patients with advanced hepatocellular carcinoma previously treated with sorafenib: 5-year results from CheckMate 040.

BACKGROUND: Nivolumab plus ipilimumab demonstrated promising clinical activity and durable responses in sorafenib-treated patients with advanced hepatocellular carcinoma (HCC) in the CheckMate 040 study at 30.7-month median follow-up. Here, we present 5-year results from this cohort. PATIENTS AND METHODS: Patients were randomized 1 : 1 : 1 to arm A [nivolumab 1 mg/kg plus ipilimumab 3 mg/kg Q3W (four doses)] or arm B [nivolumab 3 mg/kg plus ipilimumab 1 mg/kg Q3W (four doses)], each followed by nivolumab 240 mg Q2W, or arm C (nivolumab 3 mg/kg Q2W plus ipilimumab 1 mg/kg Q6W). The primary objectives were safety, tolerability, investigator-assessed objective response rate (ORR), and duration of response (DOR) per RECIST version 1.1. RESULTS: A total of 148 patients were randomized across treatment arms. At 60-month minimum follow-up (62.6-month median follow-up), the ORR was 34% (n = 17), 27% (n = 13), and 29% (n = 14) in arms A, B, and C, respectively. The median DOR was 51.2 months [95% confidence interval (CI) 12.6 months-not estimable (NE)], 15.2 months (95% CI 7.1 months-NE), and 21.7 months (95% CI 4.2 months-NE), respectively. The median overall survival (OS) was 22.2 months (34/50; 95% CI 9.4-54.8 months) in arm A, 12.5 months (38/49; 95% CI 7.6-16.4 months) in arm B, and 12.7 months (40/49; 95% CI 7.4-30.5 months) in arm C; 60-month OS rates were 29%, 19%, and 21%, respectively. In an exploratory analysis of OS by response (6-month landmark), the median OS was meaningfully longer for responders versus nonresponders for all arms. No new safety signals were identified with longer follow-up. There were no new discontinuations due to immune-mediated adverse events since the primary analysis. CONCLUSIONS: Consistent with the primary analysis, the arm A regimen of nivolumab plus ipilimumab continued to demonstrate clinically meaningful responses and long-term survival benefit, with no new safety signals in patients with advanced HCC following sorafenib treatment, further supporting its use as a second-line treatment in these patients.

Social Network Characteristics Associated with More Frequent HIV and STI Prevention Conversations: The N2 Cohort Study in Chicago.

Black cisgender sexually minoritized men (SMM) and transgender women (TW) are subgroups at highest risk of HIV and sexually transmitted infections (STIs) in the US. We sought to identify factors facilitating continued conversations - social reinforcement - surrounding HIV/STI prevention among this subgroup. Participants were recruited in Chicago from 2018 to 2019 from community health spaces. Participants provided information about themselves (level 2) and ⩽5 confidants (level 1). We used multinomial multilevel modeling to identify associations with HIV/STI prevention conversation frequency. A total of 370 participants provided information on 987 confidants (mean = 2.6). We found significantly positive associations between having biweekly or more often HIV/STI prevention conversations and a confidant being a kin family member, older by 15 years or more, racially homophilous, and emotionally close. Future interventions should harness social networks by including components that consider racial homophily, respect for elders, and strong ties, in addition to applying kin family systems interventions approaches and decreasing stigma surrounding HIV/STIs.

ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1) releases latent defense signals in stems with reduced lignin content.

There is considerable interest in engineering plant cell wall components, particularly lignin, to improve forage quality and biomass properties for processing to fuels and bioproducts. However, modifying lignin content and/or composition in transgenic plants through down-regulation of lignin biosynthetic enzymes can induce expression of defense response genes in the absence of biotic or abiotic stress. Arabidopsis thaliana lines with altered lignin through down-regulation of hydroxycinnamoyl CoA:shikimate/quinate hydroxycinnamoyl transferase (HCT) or loss of function of cinnamoyl CoA reductase 1 (CCR1) express a suite of pathogenesis-related (PR) protein genes. The plants also exhibit extensive cell wall remodeling associated with induction of multiple cell wall-degrading enzymes, a process which renders the corresponding biomass a substrate for growth of the cellulolytic thermophile Caldicellulosiruptor bescii lacking a functional pectinase gene cluster. The cell wall remodeling also results in the release of size- and charge-heterogeneous pectic oligosaccharide elicitors of PR gene expression. Genetic analysis shows that both in planta PR gene expression and release of elicitors are the result of ectopic expression in xylem of the gene ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1), which is normally expressed during anther and silique dehiscence. These data highlight the importance of pectin in cell wall integrity and the value of lignin modification as a tool to interrogate the informational content of plant cell walls.

Modelling the potential of rainwater harvesting to improve the sustainability of landscape and public garden irrigation.

Access to water for irrigating amenity landscape and public gardens is under intense pressure due to the rising competition for water between different sectors, exacerbated by increased drought risk and climate change. Rainwater harvesting (RWH) has the potential to reduce the economic impacts of restrictions on irrigation abstraction in dry years and to build resilience to future water shortages. This study investigated the hydrological viability of RWH for the landscape and public garden sector based on an analysis of five Royal Horticultural Society gardens. A RWH model was developed and combined with on-site observations, key informant interviews and GIS analyses, to estimate irrigation demands and the volumes of harvested rainfall for contrasting agroclimatic years. The results showed that gardens located in wetter regions and with low irrigation water demand to harvestable area ratio had a higher RWH potential and could almost exclusively rely on rainwater to meet irrigation demand, even in dry years. RWH potential is more limited for gardens in drier regions where they would require larger areas to harvest rainwater and for storage. Appropriately designed rainwater harvesting systems offer the potential to remove most of the risk of irrigation abstraction restrictions during dry years and associated impacts on amenity planting quality and visitor experience.

Prospective Study Demonstrates Utility of EP-QuIC in Creutzfeldt-Jakob Disease Diagnoses.

Prospectively acquired Canadian cerebrospinal fluid samples were used to assess the performance characteristics of three ante-mortem tests commonly used to support diagnoses of Creutzfeldt-Jakob disease. The utility of the end-point quaking-induced conversion assay as a test for Creutzfeldt-Jakob disease diagnoses was compared to that of immunoassays designed to detect increased amounts of the surrogate markers 14-3-3γ and hTau. The positive predictive values of the end-point quaking-induced conversion, 14-3-3γ, and hTau tests conducted at the Prion Diseases Section of the Public Health Agency of Canada were 96%, 68%, and 66%, respectively.

Characterization of CRISPR Mutants Targeting Genes Modulating Pectin Degradation in Ripening Tomato.

Tomato (Solanum lycopersicum) is a globally important crop with an economic value in the tens of billions of dollars, and a significant supplier of essential vitamins, minerals, and phytochemicals in the human diet. Shelf life is a key quality trait related to alterations in cuticle properties and remodeling of the fruit cell walls. Studies with transgenic tomato plants undertaken over the last 20 years have indicated that a range of pectin-degrading enzymes are involved in cell wall remodeling. These studies usually involved silencing of only a single gene and it has proved difficult to compare the effects of silencing these genes across the different experimental systems. Here we report the generation of CRISPR-based mutants in the ripening-related genes encoding the pectin-degrading enzymes pectate lyase (PL), polygalacturonase 2a (PG2a), and ß-galactanase (TBG4). Comparison of the physiochemical properties of the fruits from a range of PL, PG2a, and TBG4 CRISPR lines demonstrated that only mutations in PL resulted in firmer fruits, although mutations in PG2a and TBG4 influenced fruit color and weight. Pectin localization, distribution, and solubility in the pericarp cells of the CRISPR mutant fruits were investigated using the monoclonal antibody probes LM19 to deesterified homogalacturonan, INRA-RU1 to rhamnogalacturonan I, LM5 to ß-1,4-galactan, and LM6 to arabinan epitopes, respectively. The data indicate that PL, PG2a, and TBG4 act on separate cell wall domains and the importance of cellulose microfibril-associated pectin is reflected in its increased occurrence in the different mutant lines.

Elucidating the role of polygalacturonase genes in strawberry fruit softening.

To disentangle the role of polygalacturonase (PG) genes in strawberry softening, the two PG genes most expressed in ripe receptacles, FaPG1 and FaPG2, were down-regulated. Transgenic ripe fruits were firmer than those of the wild type when PG genes were silenced individually. Simultaneous silencing of both PG genes by transgene stacking did not result in an additional increase in firmness. Cell walls from ripe fruits were characterized by a carbohydrate microarray. Higher signals of homogalacturonan and rhamnogalacturonan I pectin epitopes in polysaccharide fractions tightly bound to the cell wall were observed in the transgenic genotypes, suggesting a lower pectin solubilization. At the transcriptomic level, the suppression of FaPG1 or FaPG2 alone induced few transcriptomic changes in the ripe receptacle, but the amount of differentially expressed genes increased notably when both genes were silenced. Many genes encoding cell wall-modifying enzymes were down-regulated. The expression of a putative high affinity potassium transporter was induced in all transgenic genotypes, indicating that cell wall weakening and loss of cell turgor could be linked. These results suggest that, besides the disassembly of pectins tightly linked to the cell wall, PGs could play other roles in strawberry softening, such as the release of oligogalacturonides exerting a positive feedback in softening.

Adherence to Pre-exposure Prophylaxis in Black Men Who Have Sex with Men and Transgender Women in a Community Setting in Harlem, NY.

While oral pre-exposure prophylaxis (PrEP) has proven efficacious for HIV prevention, consistent use is necessary to achieve its intended impact. We compared effectiveness of enhanced PrEP (enPrEP) adherence support to standard of care (sPrEP) among Black MSM and TGW attending a community clinic in Harlem, NY. EnPrEP included peer navigation, in-person/online support groups, and SMS messages. Self-reported adherence over previous 30 days, collected in quarterly interviews, was defined as ≥ 57%. Crude and adjusted analyses examined factors associated with adherence. A total of 204 participants were enrolled and randomized; 35% were lost to follow-up. PrEP adherence was 30% at 12-months; no intervention effect was observed (p = 0.69). Multivariable regression analysis found that lower adherence was associated with low education and depressive symptoms. We found that an enhanced adherence intervention did not improve PrEP adherence. Findings point to the need for innovative methods to improve PrEP adherence among Black MSM and TGW.Clinical Trial Registration NCT02167386, June 19, 2014.

ß-(1,4)-Galactan remodelling in Arabidopsis cell walls affects the xyloglucan structure during elongation.

MAIN CONCLUSION: Galactan turnover occurs during cell elongation and affects the cell wall xyloglucan structure which is involved in the interaction between cellulose and xyloglucan. ß-(1,4)-Galactan is one of the main side chains of rhamnogalacturonan I. Although the specific function of this polymer has not been completely established, it has been related to different developmental processes. To study ß-(1,4)-galactan function, we have generated transgenic Arabidopsis plants overproducing chickpea ßI-Gal ß-galactosidase under the 35S CaMV promoter (35S::ßI-Gal) to reduce galactan side chains in muro. Likewise, an Arabidopsis double loss-of-function mutant for BGAL1 and BGAL3 Arabidopsis ß-galactosidases (bgal1/bgal3) has been obtained to increase galactan levels. The characterization of these plants has confirmed the role of ß-(1,4)-galactan in cell growth, and demonstrated that the turnover of this pectic side chain occurs during cell elongation, at least in Arabidopsis etiolated hypocotyls and floral stem internodes. The results indicate that BGAL1 and BGAL3 ß-galactosidases act in a coordinate way during cell elongation. In addition, this work indicates that galactan plays a role in the maintenance of the cell wall architecture during this process. Our results point to an involvement of the ß-(1,4)-galactan in the xyloglucan structure and the interaction between cellulose and xyloglucan.

Branched Pectic Galactan in Phloem-Sieve-Element Cell Walls: Implications for Cell Mechanics.

A major question in plant biology concerns the specification and functional differentiation of cell types. This is in the context of constraints imposed by networks of cell walls that both adhere cells and contribute to the form and function of developing organs. Here, we report the identification of a glycan epitope that is specific to phloem sieve element cell walls in several systems. A monoclonal antibody, designated LM26, binds to the cell wall of phloem sieve elements in stems of Arabidopsis (Arabidopsis thaliana), Miscanthus x giganteus, and notably sugar beet (Beta vulgaris) roots where phloem identification is an important factor for the study of phloem unloading of Suc. Using microarrays of synthetic oligosaccharides, the LM26 epitope has been identified as a ß-1,6-galactosyl substitution of ß-1,4-galactan requiring more than three backbone residues for optimized recognition. This branched galactan structure has previously been identified in garlic (Allium sativum) bulbs in which the LM26 epitope is widespread throughout most cell walls including those of phloem cells. Garlic bulb cell wall material has been used to confirm the association of the LM26 epitope with cell wall pectic rhamnogalacturonan-I polysaccharides. In the phloem tissues of grass stems, the LM26 epitope has a complementary pattern to that of the LM5 linear ß-1,4-galactan epitope, which is detected only in companion cell walls. Mechanical probing of transverse sections of M x giganteus stems and leaves by atomic force microscopy indicates that phloem sieve element cell walls have a lower indentation modulus (indicative of higher elasticity) than companion cell walls.

The Predictive Value of Endpoint Quaking-Induced Conversion in Creutzfeldt-Jakob Disease.

Creutzfeldt-Jakob disease (CJD) is a fatal neurological illness for which accurate diagnosis is paramount. Real-time quaking-induced conversion (RT-QuIC) is a prion-specific assay with high sensitivity and specificity for CJD. The Canadian endpoint quaking-induced conversion (EP-QuIC) test is similar, but unlike RT-QuIC there is little data regarding its diagnostic utility in clinical practice. In this exploratory predictive value analysis of EP-QuIC in CJD, the negative predictive value (NPV) and positive predictive value (PPV) was 100% and 83%, respectively, with one false-positive result identified. Re-testing this sample with an optimized EP-QuIC protocol eliminated this false-positive result, leading to a PPV of 100%.

La valeur prédictive de la méthode diagnostique dite de conversion provoquée par tremblement au point final dans le cas de la maladie de Creutzfeldt-Jakob. La maladie de Creutzfeldt-Jakob (MCJ) est une maladie neurologique qui entraîne à terme un décès et pour laquelle l'établissement d'un diagnostic précis est primordial. La conversion provoquée par tremblement en temps réel (RT-QuIC en anglais) est une méthode diagnostique qui repose sur la détection de la protéine prion. Dans le cas de la MCJ, cette méthode est réputée posséder une sensibilité et une spécificité élevées. La méthode canadienne dite de conversion provoquée par tremblement au point final (EP-QuIC en anglais) se veut similaire mais, à la différence de la RT-QuIC, il existe peu de données en ce qui concerne son utilité diagnostique dans le cadre d'une pratique clinique. Dans cette analyse prédictive exploratoire de la EP-QuIC en lien avec la MCJ, la valeur prédictive négative (VPN) et la valeur prédictive positive (VPP) ont été respectivement de 100 % et de 83 %, un seul résultat faux-positif ayant été identifié. Le fait de soumettre notre échantillon à un nouveau test effectué à l'aide d'un protocole d'EP-QuIC optimisé a permis d'éliminer ce résultat faux-positif, ce qui a débouché sur une VPP de 100 %.

Complexity of the Ruminococcus flavefaciens cellulosome reflects an expansion in glycan recognition.

The breakdown of plant cell wall (PCW) glycans is an important biological and industrial process. Noncatalytic carbohydrate binding modules (CBMs) fulfill a critical targeting function in PCW depolymerization. Defining the portfolio of CBMs, the CBMome, of a PCW degrading system is central to understanding the mechanisms by which microbes depolymerize their target substrates. Ruminococcus flavefaciens, a major PCW degrading bacterium, assembles its catalytic apparatus into a large multienzyme complex, the cellulosome. Significantly, bioinformatic analyses of the R. flavefaciens cellulosome failed to identify a CBM predicted to bind to crystalline cellulose, a key feature of the CBMome of other PCW degrading systems. Here, high throughput screening of 177 protein modules of unknown function was used to determine the complete CBMome of R. flavefaciens The data identified six previously unidentified CBM families that targeted ß-glucans, ß-mannans, and the pectic polysaccharide homogalacturonan. The crystal structures of four CBMs, in conjunction with site-directed mutagenesis, provide insight into the mechanism of ligand recognition. In the CBMs that recognize ß-glucans and ß-mannans, differences in the conformation of conserved aromatic residues had a significant impact on the topology of the ligand binding cleft and thus ligand specificity. A cluster of basic residues in CBM77 confers calcium-independent recognition of homogalacturonan, indicating that the carboxylates of galacturonic acid are key specificity determinants. This report shows that the extended repertoire of proteins in the cellulosome of R. flavefaciens contributes to an extended CBMome that supports efficient PCW degradation in the absence of CBMs that specifically target crystalline cellulose.

Proteomic Screen of Brain Glycoproteome Reveals Prion Specific Marker of Pathogenesis.

Transmissible spongiform encephalopathies (TSEs) are neurodegenerative disorders caused by the presence of an infectious prion protein. The primary site of pathology is the brain characterized by neuroinflammation, astrogliosis, prion fibrils, and vacuolation. The events preceding the observed pathology remain in question. We sought to identify biomarkers in the brain of TSE-infected and aged-matched control mice using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE). Since the brain proteome is too complex to resolve all proteins using 2D-DIGE, protein samples are initially filtered through either concanavalin A (ConA) or wheat-germ agglutinin (WGA) columns. Four differentially abundant proteins are identified through screening of the two different glycoproteomes: Neuronal growth regulator 1 (NEGR1), calponin-3 (CNN3), peroxiredoxin-6 (Prdx6), and glial fibrillary acidic protein (GFAP). Confirmatory Western blots are performed with samples from TSE-infected and comparative Alzheimer's disease (AD) affected brains and their respective controls from time points throughout the disease courses. The abundance of three of the four proteins increases significantly during later stages of prion disease whereas NEGR1 decreases in abundance. Comparatively, no significant changes are observed in later stages of AD. Our lab is the first to associate the glycosylated NEGR1 protein with prion disease pathology.

Xyloglucan is released by plants and promotes soil particle aggregation.

Soil is a crucial component of the biosphere and is a major sink for organic carbon. Plant roots are known to release a wide range of carbon-based compounds into soils, including polysaccharides, but the functions of these are not known in detail. Using a monoclonal antibody to plant cell wall xyloglucan, we show that this polysaccharide is secreted by a wide range of angiosperm roots, and relatively abundantly by grasses. It is also released from the rhizoids of liverworts, the earliest diverging lineage of land plants. Using analysis of water-stable aggregate size, dry dispersion particle analysis and scanning electron microscopy, we show that xyloglucan is effective in increasing soil particle aggregation, a key factor in the formation and function of healthy soils. To study the possible roles of xyloglucan in the formation of soils, we analysed the xyloglucan contents of mineral soils of known age exposed upon the retreat of glaciers. These glacial forefield soils had significantly higher xyloglucan contents than detected in a UK grassland soil. We propose that xyloglucan released from plant rhizoids/roots is an effective soil particle aggregator and may, in this role, have been important in the initial colonization of land.

Elicitors and defense gene induction in plants with altered lignin compositions.

A reduction in the lignin content in transgenic plants induces the ectopic expression of defense genes, but the importance of altered lignin composition in such phenomena remains unclear. Two Arabidopsis lines with similar lignin contents, but strikingly different lignin compositions, exhibited different quantitative and qualitative transcriptional responses. Plants with lignin composed primarily of guaiacyl units overexpressed genes responsive to oomycete and bacterial pathogen attack, whereas plants with lignin composed primarily of syringyl units expressed a far greater number of defense genes, including some associated with cis-jasmone-mediated responses to aphids; these plants exhibited altered responsiveness to bacterial and aphid inoculation. Several of the defense genes were differentially induced by water-soluble extracts from cell walls of plants of the two lines. Glycome profiling, fractionation and enzymatic digestion studies indicated that the different lignin compositions led to differential extractability of a range of heterogeneous oligosaccharide epitopes, with elicitor activity originating from different cell wall polymers. Alteration of lignin composition affects interactions with plant cell wall matrix polysaccharides to alter the sequestration of multiple latent defense signal molecules with an impact on biotic stress responses.

Longitudinal changes in MR T1ρ/T2 signal of meniscus and its association with cartilage T1p/T2 in ACL-injured patients.

OBJECTIVE: To evaluate the longitudinal changes in meniscal T1ρ/T2 signal post-reconstruction in patients with acute anterior cruciate ligament (ACL) injury and to investigate the association with T1ρ/T2 signal in articular knee cartilage. METHOD: In this prospective study, knees of 37 patients with ACL-injury and reconstruction in addition to 13 healthy controls were scanned using magnetic resonance imaging (MRI) T1ρ/T2 mapping. Quantitative analysis of the meniscus was performed in the anterior/posterior horns of lateral/medial meniscus fourteen sub-compartments of cartilage spanning the medial/lateral area of the tibia and femoral condyles. Meniscus T1ρ/T2 signals were compared between injured, contralateral and control knees at baseline, 6-months, 1-year and 2-years using t-tests for cross-sectional comparisons and a mixed model for longitudinal comparisons. Pearson-partial correlations between meniscal and cartilage T1ρ/T2 were evaluated. RESULTS: There was a significant decrease of T1ρ/T2 signal in the posterior horn of lateral meniscus (PHLAT) of injured knees during a 2-year period. In the posterior horn of medial meniscus (PHMED), T1ρ/T2 signal of injured knees was significantly elevated at all time points post-reconstruction compared to contralateral and control knees. Within injured knees, PHMED T1ρ/T2 signal showed significant positive correlations with medial tibia (MT) cartilage T1ρ/T2 signal at all time points. CONCLUSION: A significant decrease in PHLAT T1ρ/T2 signal by 2-years suggests potential tissue recovery after ACL-injury. Elevated T1ρ/T2 signal in the PHMED of injured knees at 2-years correlating with knee cartilage T1ρ/T2 signal elevations suggests involvement of the PHMED in subacute cartilage degeneration after ACL-injury and reconstruction.

A Synthetic Glycan Microarray Enables Epitope Mapping of Plant Cell Wall Glycan-Directed Antibodies.

In the last three decades, more than 200 monoclonal antibodies have been raised against most classes of plant cell wall polysaccharides by different laboratories worldwide. These antibodies are widely used to identify differences in plant cell wall components in mutants, organ and tissue types, and developmental stages. Despite their importance and broad use, the precise binding epitope has been determined for only a few of these antibodies. Here, we use a plant glycan microarray equipped with 88 synthetic oligosaccharides to comprehensively map the epitopes of plant cell wall glycan-directed antibodies. Our results reveal the binding epitopes for 78 arabinogalactan-, rhamnogalacturonan-, xylan-, and xyloglucan-directed antibodies. We demonstrate that, with knowledge of the exact epitopes recognized by individual antibodies, specific glycosyl hydrolases can be implemented into immunological cell wall analyses, providing a framework to obtain structural information on plant cell wall glycans with unprecedented molecular precision.

Altered rPrP substrate structures and their influence on real-time quaking induced conversion reactions.

BACKGROUND: Bacterially-produced recombinant prion protein (rPrP) has traditionally been used for in vitro fibrillation assays and reagent development for prion disease research. In recent years, it has also been used as a substrate for real-time quaking-induced conversion (RT-QuIC), a very sensitive method of detecting the presence of the misfolded, disease-associated isoform of the prion protein (PrPd). Multi-centre trials have demonstrated that RT-QuIC is a suitably reliable and robust technique for clinical practice; however, in the absence of a commercial supplier of rPrP as a substrate for RT-QuIC, laboratories have been required to independently generate this key component of the assay. No harmonized method for producing the protein has been agreed upon, in part due to the variety of substrates that have been applied in RT-QuIC. METHODS: This study examines the effects of two different rPrP refolding protocols on the production, QuIC performance, and structure characteristics of two constructs of rPrP commonly used in QuIC: full length hamster and a sheep-hamster chimeric rPrP. RESULTS: Under the described conditions, the best performing substrate was the chimeric sheep-hamster rPrP produced by shorter guanidine-HCl exposure and faster gradient elution. CONCLUSIONS: The observation that different rPrP production protocols influence QuIC performance indicates that caution should be exercised when comparing inter-laboratory QuIC results.

Comparative in situ analysis reveals the dynamic nature of sclerenchyma cell walls of the fern Asplenium rutifolium.

Background and Aims: A key structural adaptation of vascular plants was the evolution of specialized vascular and mechanical tissues, innovations likely to have generated novel cell wall architectures. While collenchyma is a strengthening tissue typically found in growing organs of angiosperms, a similar tissue occurs in the petiole of the fern Asplenium rutifolium. Methods: The in situ cell wall (ultra)structure and composition of this tissue was investigated and characterized mechanically as well as structurally through nano-indentation and wide-angle X-ray diffraction, respectively. Key Results: Structurally the mechanical tissue resembles sclerenchyma, while its biomechanical properties and molecular composition both share more characteristics with angiosperm collenchyma. Cell wall thickening only occurs late during cell expansion or after cell expansion has ceased. Conclusions: If the term collenchyma is reserved for walls that thicken during expansive growth, the mechanical tissue in A. rutifolium represents sclerenchyma that mimics the properties of collenchyma and has the ability to modify its mechanical properties through sclerification. These results support the view that collenchyma does not occur in ferns and most probably evolved in angiosperms.

Differential metabolism of pectic galactan in tomato and strawberry fruit: detection of the LM26 branched galactan epitope in ripe strawberry fruit.

Antibody-based approaches have been used to study cell wall architecture and modifications during the ripening process of two important fleshy fruit crops: tomato and strawberry. Cell wall polymers in both unripe and ripe fruits have been sequentially solubilized and fractions analyzed with sets of monoclonal antibodies focusing on the pectic polysaccharides. We demonstrate the specific detection of the LM26 branched galactan epitope, associated with rhamnogalacturonan-I, in cell walls of ripe strawberry fruit. Analytical approaches confirm that the LM26 epitope is linked to sets of rhamnogalacturonan-I and homogalacturonan molecules. The cellulase-degradation of cellulose-rich residues that releases cell wall polymers intimately linked with cellulose microfibrils has been used to explore aspects of branched galactan occurrence and galactan metabolism. In situ analyses of ripe strawberry fruits indicate that the LM26 epitope is present in all primary cell walls and also particularly abundant in vascular tissues. The significance of the occurrence of branched galactan structures in the side chains of rhamnogalacturonan-I pectins in the context of ripening strawberry fruit is discussed.