Mucilage Layer Research Articles

Characterization of Two Zygnema Strains (Zygnema circumcarinatum SAG 698-1a and SAG 698-1b) and a Rapid Method to Estimate Nuclear Genome Size of Zygnematophycean Green Algae.

Zygnematophyceae green algae (ZGA) have been shown to be the closest relatives of land plants. Three nuclear genomes (Spirogloea muscicola, Mesotaenium endlicherianum, and Penium margaritaceum) of ZGA have been recently published, and more genomes are underway. Here we analyzed two Zygnema circumcarinatum strains SAG 698-1a (mating +) and SAG 698-1b (mating −) and found distinct cell sizes and other morphological differences. The molecular identities of the two strains were further investigated by sequencing their 18S rRNA, psaA and rbcL genes. These marker genes of SAG 698-1a were surprisingly much more similar to Z. cylindricum (SAG 698-2) than to SAG 698-1b. Phylogenies of these marker genes also showed that SAG 698-1a and SAG 698-1b were well separated into two different Zygnema clades, where SAG 698-1a was clustered with Z. cylindricum, while SAG 698-1b was clustered with Z. tunetanum. Additionally, physiological parameters like ETRmax values differed between SAG 698-1a and SAG 698-1b after 2 months of cultivation. The de-epoxidation state (DEPS) of the xanthophyll cycle pigments also showed significant differences. Surprisingly, the two strains could not conjugate, and significantly differed in the thickness of the mucilage layer. Additionally, ZGA cell walls are highly enriched with sticky and acidic polysaccharides, and therefore the widely used plant nuclear extraction protocols do not work well in ZGA. Here, we also report a fast and simple method, by mechanical chopping, for efficient nuclear extraction in the two SAG strains. More importantly, the extracted nuclei were further used for nuclear genome size estimation of the two SAG strains by flow cytometry (FC). To confirm the FC result, we have also used other experimental methods for nuclear genome size estimation of the two strains. Interestingly, the two strains were found to have very distinct nuclear genome sizes (313.2 ± 2.0 Mb in SAG 698-1a vs. 63.5 ± 0.5 Mb in SAG 698-1b). Our multiple lines of evidence strongly indicate that SAG 698-1a possibly had been confused with SAG 698-2 prior to 2005, and most likely represents Z. cylindricum or a closely related species.

The crucial role of yeasts in the wet fermentation of coffee beans and quality

The objective of this study was to investigate the role of yeasts in the wet fermentation of coffee beans and their contribution to coffee quality using a novel approach. Natamycin (300 ppm) was added to the fermentation mass to suppress yeast growth and their metabolic activities, and the resultant microbial ecology, bean chemistry and sensory quality were analyzed and compared to non-treated spontaneous fermentation we reported previously. The yeast community was dominated by Hanseniaspora uvarum and Pichia kudriavzevii and grew to a maximum population of about 5.5 log CFU/g in the absence of Natamycin, while when Natamycin was added yeasts were suppressed. The major bacterial species in both the spontaneous and yeast-suppressed fermentations included the lactic acid bacteria Leuconostoc mesenteroides and Lactococcus lactis, the acetic acid bacteria Gluconobacter cerinus and Acetobacter persici and the Enterobacteriaceae Enterobacter, Citrobacter and Erwinia. For both fermentations, the mucilage layers were completely degraded by the end of the process and the absence of yeast activities had no significant impact on mucilage degradation. During fermentation, reducing sugars were consumed while lactic acid was accumulated inside the beans, and its concentration was significantly higher in the spontaneous fermentation (3 times) than that where yeasts were suppressed by Natamycin. Glycerol was detected with a concentration of 0.08% in the absence of Natamycin and was not identified when Natamycin was added. Green beans fermented with yeast growth contained a higher amount of isoamyl alcohol (21 times), ethanol (3.7 times), acetaldehyde (8 times), and ethyl acetate (25 times) compared to beans fermented in the absence of yeast activities, which remained higher in the former after roasting. Beans fermented without yeast activities had a mild fruity aroma, and lower sensory scores of fragrances (7.0), flavor (6.5), acidity (6.3), body (7.0) and overall score (6.5) compared to the former. These findings demonstrated the crucial roles of yeasts in wet fermentation of coffee beans and for producing high quality coffee.

The novel features of Plantagoovata seed mucilage accumulation, storage and release

Seed mucilage polysaccharide production, storage and release in Plantagoovata is strikingly different to that of the model plant Arabidopsis. We have used microscopy techniques to track the development of mucilage secretory cells and demonstrate that mature P.ovata seeds do not have an outer intact cell layer within which the polysaccharides surround internal columellae. Instead, dehydrated mucilage is spread in a thin homogenous layer over the entire seed surface and upon wetting expands directly outwards, away from the seed. Observing mucilage expansion in real time combined with compositional analysis allowed mucilage layer definition and the roles they play in mucilage release and architecture upon hydration to be explored. The first emergent layer of hydrated mucilage is rich in pectin, extremely hydrophilic, and forms an expansion front that functions to ‘jumpstart’ hydration and swelling of the second layer. This next layer, comprising the bulk of the expanded seed mucilage, is predominantly composed of heteroxylan and appears to provide much of the structural integrity. Our results indicate that the synthesis, deposition, desiccation, and final storage position of mucilage polysaccharides must be carefully orchestrated, although many of these processes are not yet fully defined and vary widely between myxospermous plant species.

Mucilage inhibits germination of desert ephemeral Nepeta micrantha seed under moderate osmotic stress and promotes recovery after release of this stress

Mucilage is considered to play an important role in the survival of seeds in harsh desert environments. Nepeta micrantha is an ephemeral plant of the Gurbantungut Desert, China. The outer surface of N. micrantha nutlets contains a layer of mucilage. We hypothesised that mucilage improves germination during and after osmotic stress. Germination of both intact and demucilaged nutlets under different polyethylene glycol (PEG)-simulated drought stress was tested at the optimal light and temperature conditions. Germination of intact and demucilaged nutlets decreased with an increase in PEG concentration. However, there were no significant differences in germination between intact and demucilaged nutlets at the same PEG concentration, except at 15% PEG. Recovery percentage and final germination of intact nutlets were considerably higher than that of demucilaged nutlets after treatment with 15% PEG. These findings demonstrate that mucilage contributes significantly to drought tolerance ofN. micrantha nutlets by decreasing germination under moderate osmotic stress and aiding germination after the release of this stress.

Seed germination of Southern Chihuahuan desert cacti: Effect of mucilage, light and phytohormones

The aim of this study was to evaluate the effect of mucilage and its removal, as well as phytohormones [gibberellic acid (GA3) and indole-3-acetic acid (IAA)] in light and in darkness on germination of five cactus species (Coryphanta maiz-tablasensis, Echinocactus platyacanthus, Ferocactus latispinus, Ferocactus pilosus and Stenocereus queretaroensis) from the Chihuahuan Desert. Three of them, C. maiz-tablasensis, E. platyacanthus and F. pilosus, are at risk. The mucilage layer occurred in all species. The sterilization treatment removed the mucilage even from the micropyle. Mucilage resulted in higher germination percentage in E. platyacanthus (88.5 % vs. 21.1 % without mucilage), F. latispinus (88.5 % vs. 48.2 %) and S. queretaroensis (96.0 % vs. 1.0 %), as well as a lower germination time for E. platyacanthus (10.0 days vs. 19.5 days without mucilage), F. pilosus (14.1 days vs. 16.4 days) and F. latispinus (7.8 days vs. 14.0 days). GA3 did affect germination percentage in E. platyacanthus (higher at 500 and 1000 mg l−1 than at 50 and 100 mg l−1), F. latispinus (higher at 1000 mg l−1 of GA3 than at the control and at the other concentrations) and F. pilosus (higher at 1000 mg l−1 of GA3 than at control and 50 mg l−1). The interaction of mucilage layer and GA3 was only significant for F. latispinus in that seeds with mucilage had higher germination at 0, 50, 100 and 250 mg l−1 of GA3 than seeds without mucilage, but at 500 and 1000 mg l−1 germination was high with and without mucilage. Most cactus seeds had no germination in darkness and auxins did not promote germination. Mucilage covers the micropyle and seeds without mucilage were internally more colored than seeds with mucilage in most species. We suggest that mucilage layer in the micropyle can function like a barrier regulating the passage of water to the inner seed.

Effect of Bacillus tequilensis SALBT crude extract with pectinase activity on demucilation of coffee beans and juice clarification.

Pectinases are a group of enzymes, which catalyzethe breakdown of pectin with numerous applications in various industries. Microbes are the predominant pectinase producers. In the present study, bacterial species were isolated from the soil of a vegetable and fruit dumpyard area in a market. The species screened and isolated were identified as Bacillus tequilensis SALBT, and the media and culture conditions were optimized for enhanced production of total pectinases.Maximum pectinolytic activity was observed with 1.5% (w/v) pectin concentration with a combination of yeast extract as nitrogen source and MgSO4 as a metal ion source. Carbon/nitrogen in 2:1 ratio (w/v) yielded the maximum pectinase production with pH and temperature of the medium of 7.5°C and 40°C, respectively. Pectinase activity was determined by the dinitrosalicylic acid method. The pectinase production was relatively stable in the presence of various surfactants like Tween (20, 40, 60, and 80) and sodium dodecyl sulfate (SDS), whereas Triton X-100 showed an inhibitory effect. Mass production of the enzyme in optimized media and partial purification was performed by ammonium sulfate precipitation followed by dialysis. The approximate molecular weight of the partially purified pectinase was found to be 35 kDa by SDS-polyacrylamide gel electrophoresis. Application studies such as demucilaging coffee beans and juice clarification were also performed. The findings revealed that B. tequilensis SALBT with pectinase activity has the ability to remove the mucilage layer of pulped coffee seeds, and the partially purified pectinases found to be effective in clarifying juice.

Natural Variation Reveals a Key Role for Rhamnogalacturonan I in Seed Outer Mucilage and Underlying Genes.

On imbibition, Arabidopsis (Arabidopsis thaliana) seeds release polysaccharides from their epidermal cells that form a two-layered hydrogel, termed mucilage. Analysis of a publicly available data set of outer seed mucilage traits of over 300 accessions showed little natural variation in composition. This mucilage is almost exclusively made up of rhamnogalacturonan I (RGI), highlighting the importance of this pectin for outer mucilage function. In a genome-wide association study, observed variations in polymer amount and macromolecular characteristics were linked to several genome polymorphisms, indicating the complexity of their genetic regulation. Natural variants with high molar mass were associated with a gene encoding a putative glycosyltransferase called MUCILAGE-RELATED70 (MUCI70). muci70 insertion mutants produced many short RGI polymers that were highly substituted with xylan, confirming that polymorphism in this gene can affect RGI polymer size. A second gene encoding a putative copper amine oxidase of clade 1a (CuAOα1) was associated with natural variation in the amount of RGI present in the outer mucilage layer; cuaoα1 mutants validated its role in pectin production. As the mutant phenotype is unique, with RGI production only impaired for outer mucilage, this indicates that CuAOα1 contributes to a further mechanism controlling mucilage synthesis.

Developmental characteristics of grapevine seedlings root border cells and their response to ρ-hydroxybenzoic acid

ρ-hydroxybenzoic acid (4-HBA) is one of the major autotoxins that cause grapevine replant disease. Root border cells (RBCs) play an important role in plant defense. Although RBCs have been investigated in many plants, relevant information in grapevines is limited. In this study, we aimed to investigate the developmental characteristics of RBCs in the grapevine (Vitis riparia × Vitis labrusca) ‘Beta’ and their response to 4-HBA stress. RBCs were observed under a laser scanning confocal microscope. The phenolic acid composition of RBCs slime was determined by high-performance liquid chromatography. The level of gene expression was determined by quantitative real-time polymerase chain reaction. Grapevine RBCs have high biological activity, contain starch granules, and are surrounded by a mucilage layer. Root treatments using different concentrations of 4-HBA affected the development of RBCs and root growth, and induced the secretion of salicylic acid from the RBCs, which can stimulate, induce, and maintain the activity of antioxidant enzymes to some extent in the cells under 4-HBA stress. Grapevine RBCs may resist 4-HBA stress by increasing its number and enhancing their secondary metabolism and SA accumulation, which can induce the antioxidant defense system of the cells.

Effect of Co-Inoculation with Pichia fermentans and Pediococcus acidilactici on Metabolite Produced During Fermentation and Volatile Composition of Coffee Beans

Removal of the mucilage layer of coffee fruits by a fermentation process has became an interesting strategy to improve coffee quality, which is able to assist the formation of flavored molecules. In this study, four sets of inoculation protocols were evaluated using ripe and immature coffee fruits, respectively, including (i) pure culture fermentation with Pichia fermentans, (ii) pure culture fermentation with Pediococcus acidilactici, (ii) combined fermentation with P. fermentans and P. acidilactici, and (iv) spontaneous, non-inoculated control. The initial pulp sugar concentration of ripe coffee fruits (0.57 and 1.13 g/L glucose and fructose content, respectively) was significantly higher than immature coffee pulp (0.13 and 0.26 g/L glucose and fructose content, respectively). Combined inoculation with P. fermentans and P. acidilactici of ripe coffee beans increased pulp sugar consumption and production of metabolites (lactic acid, ethanol, and ethyl acetate), evidencing a positive synergic interaction between these two microbial groups. On the other hand, when immature coffee fruits were used, only pure culture inoculation with P. fermentans was able to improve metabolite formation during fermentation, while combined treatment showed no significant effect. Altogether, 30 volatile compounds were identified and semi-quantified with HS- solid phase microextraction (SPME)-gas chromatography coupled to mass spectrophotometry (GC/MS) in fermented coffee beans. In comparison with pure cultures and spontaneous process, combined treatment prominently enhanced the aroma complexity of ripe coffee beans, with a sharp increase in benzeneacetaldehyde, 2-heptanol, and benzylalcohol. Consistent with the monitoring of the fermentation process, only P. fermentans treatment was able to impact the volatile composition of immature coffee beans. The major impacted compounds were 2-hexanol, nonanal, and D-limonene. In summary, this study demonstrated the great potential of the combined use of yeast and lactic acid bacteria to improve fermentation efficiency and to positively influence the chemical composition of coffee beans. Further studies are still required to investigate the mechanisms of synergism between these two microbial groups during the fermentation process and influence the sensory properties of coffee products.

Lactic acid bacteria: what coffee industry should know?

During coffee processing, lactic acid bacteria (LAB) from multiple ecosystems (water, native soil, air, and plant) find in the cherry pulp a rich environment for their development. They utilize pulp substrate as a source of carbon and nitrogen to produce significant amounts of lactic acid. This natural fermentation is purposely used by coffee growers to promote an efficient removal of the mucilage layer adhering to the fruits, before storage and transport of the coffee beans. Besides lactic acid, LAB metabolism produces a variety of compounds from the utilization of citrate and the catabolism of amino acids. Recent studies have demonstrated that these metabolites have a complementary function in the formation of taste and flavor precursors of coffee beverages. However, the possibility of improving coffee quality by the use of LAB has largely been ignored. This review considers the importance of LAB associated with coffee processing, exploring their diversity and metabolism and influences on coffee quality. The selection of appropriate LAB strains, alone or in combination with yeasts, is a promising research line in a near future, leading to new perspectives on coffee quality.

Composition and physicochemical properties of outer mucilage from seeds of Arabidopsis natural accessions.

Arabidopsis thaliana (Arabidopsis) seeds are myxospermous and release two layers of mucilage on imbibition. The outer layer can be extracted with water facilitating the analysis of its major constituent, polysaccharides. The composition and properties of outer mucilage have been determined for 306 natural accessions and six control genotypes to generate a data set comprising six traits measured in four biological replicates for each. Future exploitation of this data is possible in a range of analyses and should yield information concerning genetic diversity, underlying genetic factors and the biological function of mucilage as an adaptive trait.

Obtaining a novel mucilage from mutamba seeds exploring different high-intensity ultrasound process conditions

We evaluated the effect of ultrasonic power (200–600 W) and process time (1–7 min) on the recovery of a novel polysaccharide from mutamba (Guazuma ulmifolia Lam.) seeds applying high-intensity ultrasound. Ultrasound process conditions intensification gradually was removing the mucilage layer around the hydrated seeds. Then, the scanning electron micrographs showed that the mucilage was removed completely at the highest applied energy density (10,080 J/mL). Although the colour of mutamba seed mucilage (MSM) have been changed due to increase of energy density, it not affects its practical use because the MSM can be purified to remove impurities. The results obtained in this study demonstrated that the ultrasound process conditions intensification did not affect the primary structure of MSM according to ζ-potential, FTIR spectrum, and monosaccharide residues data. In conclusion, ultrasound process conditions intensification allows the full recovery of the MSM at a short process time (7 min) without altering its quality and the primary structure.

Efficient coffee beans mucilage layer removal using lactic acid fermentation in a stirred-tank bioreactor: Kinetic, metabolic and sensorial studies

Post-harvest coffee processing involves a microbial process to remove the mucilage layer adhering to the fruits, prior to storage and transport of the coffee beans. In this study, coffee mucilage removal was done using lactic acid fermentation in a stirred-tank bioreactor (STR). Fermentation assays were done with or without the addition of starter culture (i.e., Lactobacillus plantarum LPBR01), and kinetic parameters, including microbial growth, sugar pulp consumption and metabolite production, were studied. High lactic acid bacteria (reaching 10.7 log CFU/ml at 10 h) were obtained in the STR process with the starter culture, which led to a high lactic acid productivity (0.366 g/l h) and a pH decrease to below 4.0 during the initial 10 h. A temporal analysis using Illumina high-throughput 16S rRNA Gene Sequencing (HTS) showed the Lactobacillus genus's dominance in the inoculation process, as it reached over 88% of read sequences at the end of fermentation, while the Leuconostocaceae family was the dominant bacterial group in the spontaneous treatment. The STR fermentation process led to the production of coffee beans with richer aroma composition and beverages with a notable increase in the sensorial analysis of the coffee beverages compared to those resulting from the conventional process. This new fermentation model can be used to do controlled bean fermentation to supply the coffee industry with homogeneous and high-quality coffee beans.

The role of COBRA-LIKE 2 function, as part of the complex network of interacting pathways regulating Arabidopsis seed mucilage polysaccharide matrix organization.

The production of hydrophilic mucilage along the course of seed coat epidermal cell differentiation is a common adaptation in angiosperms. Previous studies have identified COBRA-LIKE 2 (COBL2), a member of the COBRA-LIKE gene family, as a novel component required for crystalline cellulose deposition in seed coat epidermal cells. In recent years, Arabidopsis seed coat epidermal cells (SCEs), also called mucilage secretory cells, have emerged as a powerful model system for the study of plant cell wall components biosynthesis, secretion, assembly and de muro modification. Despite accumulating data, the molecular mechanism of COBL function remains largely unknown. In the current research, we utilized genetic interactions to study the role of COBL2 as part of the protein network required for seed mucilage production. Using correlative phenotyping of structural and biochemical characteristics, unique features of the cobl2 extruded mucilage are revealed, including: 'unraveled' ray morphology, loss of primary cell wall 'pyramidal' organization, reduced Ruthenium red staining intensity of the adherent mucilage layer, and increased levels of the monosaccharides arabinose and galactose. Examination of the cobl2cesa5 double mutant provides insight into the interface between COBL function and cellulose deposition. Additionally, genetic interactions between cobl2 and fei1fei2 as well as between each of these mutants to mucilage-modified 2 (mum2) suggest that COBL2 functions independently of the FEI-SOS pathway. Altogether, the presented data place COBL2 within the complex protein network required for cell wall deposition in the context of seed mucilage and introduce new methodology expending the seed mucilage phenotyping toolbox.

Aquatic insects in the forest canopy: a new genus of moth flies (Diptera: Psychodidae) developing in slime on aerial roots

ABSTRACTMany hemiepiphytic plants secrete a thick layer of mucilage to limit desiccation and protect against fungal pathogens. With its stable moisture and protected location, this mucilage constitutes a potentially attractive microhabitat for small animals; however, until now, no animal species have been recorded from it. Larvae of a psychodid fly were collected from the mucilage of a hemiepiphytic Araceae in Braulio Carillo National Park, Costa Rica. Rearing of the larvae yielded specimens of pupae and one adult male described here as Mucomyia emersa Kvifte and Curler gen. nov. sp. nov. An additional species from Costa Rica, Mucomyia browni Kvifte sp. nov., is described based on adult males from the Zurquí de Moravia forest reserve. Mucomyia belongs to tribe Psychodini, which comprises both habitat generalists and specialists. The new species are morphologically similar to those in Philosepedon s. str. and Eurygarka, both of which are known to develop in snail carrion. It is premature to speculate about whether or not species in the new genus are restricted to hemiepiphyte mucilage.http://www.zoobank.org/urn:lsid:zoobank.org:pub:37CD136B-53D8-4D3E-A34A-3BE4859045E5

Review and Evaluation of Root Respiration and of Natural and Agricultural Processes of Soil Aeration

Core Ideas Movement of O2 in the soil is mainly diffusive. Respiration consists of plant root and microbial O2 uptake, roughly of the same magnitude. Reduced O2 and elevated CO2 concentrations negatively affect plant growth and productivity. O2 concentration, air content, and ODR are good quantifiers for O2 availability to plant roots. Adding bubbles or H2O2 to irrigation and injecting air to soil showed mostly favorable results. Soil aeration processes and status are reviewed with regard to different soil, climatic, land‐use, and crop types and with regard to diffusive and advective flow mechanisms. Factors affecting aeration status and its quantifiers are discussed and active soil aeration (“oxygation”) practices are presented. Movement of O2 from the soil surface into the soil profile and its transport into soil aggregates and toward plant roots is mainly diffusive. In most circumstances, root respiration is constrained by vertical O2 diffusion from the atmosphere to the root zone and by the diffusive resistance of the mucilage layer. Several O2–diffusive flow models are proposed and discussed with regard to the different geometries, relevant length scales, boundary conditions, and sinks. Soil aeration by advective O2 flow, driven by barometric pressure changes, may also be significant in dry, coarse‐textured soils with no underlying impermeable layers. Respiration in the soil consists mainly of plant root and microbial O2 uptake, which are roughly of the same magnitude and strongly correlated through symbiotic and competitive relationships. The bulk, areal soil respiration rate varies from several to tens of grams of O2 per square meter per day depending on soil cover: fallow, pasture, forests, unirrigated and irrigated, cropped fields, and orchards (in general increasing order). Soil respiration rate is also affected by climatic conditions, where a temperature difference of 10°C increases O2 consumption (and CO2 production) two‐ to threefold. The ratio between emitted CO2 and inspired O2 (respiratory quotient) is not unity (on a molar basis) but rather depends on the types of respiring populations and environmental conditions. Reduced O2 and elevated CO2 concentrations negatively affect plant growth and productivity. These conditions are correlated mostly with wet and warm soils, such as intensively irrigated fields with fine‐textured soils (high water retention) during the summer. Oxygen‐availability quantifiers such as O2 concentration, air content, and O2 diffusion rate are superior to other quantifiers such as soil properties (e.g., soil texture, porosity) and redox potential. In the last few decades, several active aeration methods have been proposed and evaluated, such as adding air or O2 bubbles or H2O2 to the irrigation water and air injection into the soil. Although these methods have given mainly positive results, none is widely used in agricultural practice, due mainly to a lack of profitability potential, field‐scale proof demonstration, and a coherent protocol for field application.

Mannans and endo-β-mannanase transcripts are located in different seed compartments during Brassicaceae germination.

Mannans but not endo-β-mannanases are mainly found in the mucilage layer of two Brassicaceae seeds. Nonetheless, mannanase mobilization from inner to outer seed layers cannot be ruled out. The contribution of endo-β-mannanase (MAN) genes to the germination of the wild-type Sisymbrium officinale and cultivated Brassica rapa (Brassicaceae) species has been explored. In both species, mannans have been localized to the imbibed external seed coat layer (mucilage) by fluorescence immunolocalization and MAN enzymatic activity increases in seeds as imbibition progresses, reaching a peak before 100% germination is achieved. The MAN gene families have been annotated and the expression of their members analyzed in vegetative and reproductive organs. In S. officinale and B. rapa, MAN2, MAN5, MAN6, and MAN7 transcripts accumulate upon seed imbibition. SoMAN7 is the most expressed MAN gene in S. officinale germinating seeds, as occurs with its ortholog in Arabidopsis thaliana, but in B. rapa, the most abundant transcripts are BrMAN2 and BrMAN5. These genes (MAN2, MAN5, MAN6, and MAN7) are localized, by mRNA in situ hybridization, to the micropylar at the endosperm layer and to the radicle in S. officinale, but in B. rapa, these mRNAs are faintly found to the micropylar living seed coat layer and are mainly present at the radicle tip and the vascular bundles. If the domestication process undergone by B. rapa is responsible for these different MAN expression patterns, upon germination remains to be elucidated. Since mannans and MAN genes are not spatially distributed in the same seed tissues, a movement of MAN enzymes that are synthesized with typical signal peptides from the embryo tissues to the mucilage layer (via apoplastic space) is necessary for the mannans to be hydrolyzed.

Atomic force microscopy (AFM) application to diatom study: review and perspectives

Atomic force microscopy (AFM) allows high image resolution, based on slight differences in surface height and on imaging transparent structures, thus, is an excellent type of microscopy for imaging nano-sized objects, such as diatoms. Currently and since 1992, the number of publications applying AFM on diatom studies has increased significantly. Our study considers different aspects related with AFM and diatom samples preparation, AFM types and its application in studies of taxonomy, biomineral formation, ultrastructure, mucilage layers, and micromechanical properties. We also present new AFM data highlighting the taxonomical importance of Amphipleura pellucida. From our knowledge, it is the first general review that compiles all the works carried out on Atomic force microscopy (AFM) applied to diatoms, highlighting the AFM advantages regarding the study of these microorganisms as a whole.

Integument cell gelatinisation\u2014the fate of the integumentary cells in Hieracium and Pilosella (Asteraceae)

Members of the genera Hieracium and Pilosella are model plants that are used to study the mechanisms of apomixis. In order to have a proper understanding of apomixis, knowledge about the relationship between the maternal tissue and the gametophyte is needed. In the genus Pilosella, previous authors have described the specific process of the “liquefaction” of the integument cells that surround the embryo sac. However, these observations were based on data only at the light microscopy level. The main aim of our paper was to investigate the changes in the integument cells at the ultrastructural level in Pilosella officinarum and Hieracium alpinum. We found that the integument peri-endothelial zone in both species consisted of mucilage cells. The mucilage was deposited as a thick layer between the plasma membrane and the cell wall. The mucilage pushed the protoplast to the centre of the cell, and cytoplasmic bridges connected the protoplast to the plasmodesmata through the mucilage layers. Moreover, an elongation of the plasmodesmata was observed in the mucilage cells. The protoplasts had an irregular shape and were finally degenerated. After the cell wall breakdown of the mucilage cells, lysigenous cavities that were filled with mucilage were formed.

The conidial mucilage, natural film coatings, is involved in environmental adaptability and pathogenicity of Hirsutella satumaensis Aoki

The Hirsutella genus is very special asexually-reproducing pathogens of insects by reduced sporulation, host specificity and spores covered by a thick mucilage layer. However, the ecological function of conidial mucilage remains elusive. In this study, the possible ecological role of conidial mucilage from the entomopathogenic fungus Hirsutella satumaensis was functionally investigated through tolerance, adherence and insect bioassays involving aerial conidia (AC) and mucilage-free conidia (MFC). Measurements of hydrophobicity using microbial adhesion to hydrocarbons (MATH) indicated that mucilage is main contributor to the surface hydrophobicity of AC. When subjected in tolerance assays to extreme temperatures, high chemical pressure, extended exposure to ultraviolet radiation and cold stress, AC produced more colonies, exhibited higher conidiation and germination percentages than those of MFC. In adhesion assays, MFC displayed an approximately 40% reduction in adherence to locust, dragonfly cuticle and onion epidermis when washed with 0.05% Tween 20. Similarly, Galleria mellonella and Plutella xylostella larvae infected with mucilage-producing AC experienced a relatively higher mortality rate. Our findings suggest that mucilage is critical to the ecological adaptability of H. satumaensis, where it plays positive roles on maintenance of spore surface hydrophobicity, enhancement of spore resistance to extreme environments and strengthening of spore adhesion and host pathogenicity.