Introduction
Flax (Linum usitatissimum L.) which belongs to the family Linaceae is a commercial crop grown for the production of i) cellulosic fibres, manufactured in textile and composite industries and ii) linseed oil, used in varnishes and paints. In addition to these technical applications, the benefits of flax seeds for human and animal nutrition have been abundantly documented (e.g. Ganorkar and Jain, 2013). Proteins (e.g. Oomah and Mazza, 1993, Rabetafika etal., 2011, Singer etal., 2011), lignans (Hyvärinen etal., 2006, Touré and Xueming, 2010) together with mucilages (soluble fibres) have been traditionally used for medical purposes to reduce gastritis, blood cholesterol, atherosclerosis, diabetes, nephritis, and/or hormone-dependent cancers (e.g. Rubilar etal., 2010, Wanasundara and Shahidi, 1998). The possible biological activity of peptides has also been investigated (Marambe etal., 2008). The emulsifying and foaming properties of proteins were shown to be enhanced by the presence of mucilages (Dev and Quensel, 1986, Mazza and Biliaderis, 1989, Susheelammma, 1989). Mucilages were also used as stabilizer or texture ingredients in food (Anttila etal., 2008).
According to the flax literature, flax-seed mucilages represent a few to ∼10% of the seed mass. They can be purified into neutral and acidic polymers (for a review see Naran etal., 2008). Neutral polymers consist of arabinoxylans (AX) of high molar mass (Warrand etal., 2005). They are built of typical β-d-xylan backbones, with t-Ara residues attached to both the O-2 and O-3 of some xylose residues; AX may be weakly acidic, owing to t-GlcA residues also attached to the xylan chain (Naran etal., 2008). Several populations of AX-rich polymers have been distinguished according to their molecular size which might have similar Ara/Xyl ratio but vary in the apparent degree of substitution with additional Gal and Fuc side-chain residues (Warrand etal., 2005). Acidic polymers mainly consist of rhamnogalacturonan I (RGI) i.e. a backbone made of repeating dimers of →2)-α-l-rhamnose-(1→4)-β-d-galactosyluronic acid-(1 →, substituted by the rare sugar l-Gal (Anderson, 1933) and l-Fuc residues attached to the O-3 position of rhamnose instead of the O-4 position (Naran etal., 2008). The ratio of Gal to Rha was specifically determined in a commercial yellow variety to be in the range of 0.54–0.81 (Warrand etal., 2003). Mucilages collected at moderate temperatures were particularly enriched in GalA (Fedeniuk and Biliaderis, 1994, Wannerberger etal., 1991) and some homogalacturonan-like structures (named HG) were identified (Paynel etal., 2013, Qian etal., 2012a).
With the aim to enhance the value of mucilages by breeding, several papers have dealt with the genotype influence on mucilage content, composition and/or rheological properties (Bhatty, 1993, Cui etal., 1996, Diederichsen etal., 2006, Fedeniuk and Biliaderis, 1994, Oomah etal., 1995, Wannerberger etal., 1991). Measuring the mucilage viscosity as soon as it was extracted (parameter named MIV for mucilage indicator value), Diederichsen etal. (2006) observed a large variability for MIV within the world flax seed collection, but no correlation could be evidenced with the mass or colour of seeds, nor with the geographic region of origin of the accession. On the other hand, Oomah etal. (1995) studying 109 accessions, reported a high variability of Rha/Xyl ratio. In a subsequent paper, Cui etal. (1996) pointed out that some yellow linseeds produced viscous AX enriched mucilages, while brown seeds might produce AX enriched mucilages with low viscosity properties. The difficulty to get a clear idea of a possible relation between composition and rheological properties of mucilage might originate from the high temperature used for the extraction of mucilages, leading to a mixture of soluble mucilages and mucilages more tightly linked with the epidermis cell-walls (Naran etal., 2008, Paynel etal., 2013). Indeed, Fedeniuk and Biliaderis (1994) clearly indicated that mucilages extracted either at 4°C or at 80°C were characterized by a high percentage of either GalA or Xyl. After purification on anion exchange chromatography of the former (4°C extracted) mucilage, the neutral polysaccharide was shown to have a higher intrinsic viscosity than its acidic counterpart. When extracted at moderate temperature from 5 lines, soluble mucilages – without any further fractionation – were also shown to exhibit increasing viscosity with increasing xylose residues (Wannerberger etal., 1991).
For better understanding of the variability of biochemical data and evaluation of interactions between different characters we needed to use wide scale of flax genetic diversity. Since the beginning of the 20th century, Vavilov Institute in St Petersburg has been involved in the development and management of plant genetic resources. Among them, flax accounted for six thousands of accessions from all over the world. The objectives of the present study were (i) to investigate the genetic variability of mucilage composition and properties in 18 lines of flax selected under St Petersburg growth-conditions and (ii) to consider the mucilage features in relation to vegetative period, seed weight, plant height, colours and shapes of flowers and seeds. Following Fedeniuk and Biliaderis (1994) and Paynel etal. (2013) working at 4°C or moderate temperature, we collected soluble mucilages at temperatures<30°C. Two characters, important for breeding, vegetative period and seed production, were considered for the line choice, in addition to the colour of seeds (and flower) and the plant use (oil or fibres). Colours of the flowers were noted as the trait which can help to determine the degree of purity of the seeds and they can also play a part in selection (Dubois etal., 1979). To our knowledge, no data are available concerning the impact of vegetative period (Vp), size of seeds, colours and shapes of flowers on the composition and properties of soluble mucilages. In this paper, we focused our study on the composition (in term of polysaccharides and proteins) and physico-chemical properties (molar mass and viscosity) of soluble early-released mucilages.
Thus, the data dealt specifically on soluble mucilages naturally extruded in water at moderate temperature. These mucilages are mainly located in the cell junctions and the outer tangential wall of the epidermial cells (Attoumbré etal., 2011) and on seed hydration, they adsorb water and diffuse to form a gel-like capsule around the seed. Over longer hydration time, the outer tangential cell-wall would be partly disrupted/hydrolysed and cell-wall cross-linked mucilages would be released (Naran etal., 2008). The former soluble mucilages are thought i) to help in dispersal by sticking to animals, and in the adhesion to soil, ii) to facilitate the seed hydration or to resist desiccation, iii) to attract microorganisms in the rhizosphere (Western, 2012, Yang etal., 2012). Together with the lately released mucilages, they provide a nutrient reserve-material during germination (Yang etal., 2012). On the other hand, expanded mucilages prevent the seed burying into deep soil levels, interacting with fine soil particles of upper soil levels, where they can easily germinate. Such ecological/biological/agronomical significance of our results will be approached in the discussion.
Section snippets
Plant material
A set of 18 lines was selected from accessions of Vavilov Institute collection (Russia) of flax genetic resources having different origin (Table1). Self-pollination of individual plants with purity control was made for 6 generations. After this, the lines were multiplied and some lines passed through the genetic analyses of flower and seed colours (Brutch etal., 2001, Brutch and Porokhovinova, 2005, Brutch etal., 2005). These lines were also characterized by their differences in vegetative
Vegetative period, seed size and production characters
Vegetative period (Vp) is a very important character for breeding. In this current investigation, we used 8 early lines (70–74d): 5 brown seeded and 3 variegated seeded and 3 late lines (89–91d), 1 brown and 2 yellow linseeds (Table3). The earliest genotypes originated from Russia, and the latest ones came from Germany and The Netherlands. Therefore, our sampling presented high diversity of this character and its combinations with seed colour.
Seed morphology was approached using the three
Conclusion
Lines currently evaluated were chosen for their different origin, their lateness/earliness agronomical characters, their useand their seed morphological and colour characters. Interestingly, they presented 14 (over 46) high variable (SeV, a, Gal, Gal/Rha, RG1b/AX, MrFr1) and very high variable (pr, pr/m, ag, ag/m, ag/pr, Glc, HG, MrFr3) traits which indicated some intraspecific diversity. Worth to note, the vegetative period (CV 9%) significantly impacted the seed size (SeV,+), the mucilage
Acknowledgements
The work was supported by the Interreg IVA (South) project 4044 Flax and by the Council of Haute-Normandie. Part of the subsidies for the collaboration with the colleagues from St Petersburg were provided by PBS-UMR 6270 CNRS laboratory. Glyco-mev laboratory (University of Rouen) is thanked for GC access. Professors D. Le Cerf and L. Picton are thanked for the access to SEC-MALLS.
Fractionation and structural characterization of six purified rhamnogalacturonans type I from flaxseed mucilage
2017, Food Hydrocolloids
An improved method for the qualitative fractionation of water-soluble mucilage (WSM) polysaccharides isolated from flaxseed (Linum usitatissimum) comprising ion-exchange chromatography coupled with an evaporative light scattering detector was developed. One neutral fraction (NWSM) and six acidic fractions (AWSM-1 to AWSM-6) were purified. The molecular weights of NWSM, AWSM-1 - AWSM-6, determined using SEC/MALLS, were 1300kDa, 756.4kDa, 718.8kDa, 505.6kDa, 457.5kDa, 354.8kDa and 593.2kDa, respectively. Monosaccharide composition and linkage analysis confirmed that NWSM was an arabinoxylan with a (1→4)-xylan backbone to which terminal arabinose residues and putative short-chain monosaccharides were attached at positions 2 and/or 3. On the other hand, it was shown that the six acidic fractions had similar rhamnogalacturonan I (RG-I) blocks that can be monosubstituted at O-3 position of rhamnose, mostly by terminal galactose or terminal fucose and occasionally by short side-chains of neutral monosaccharides. The calculated rhamnose/galacturonic acid ratio was from 1.22 to 0.85, which remained virtually unchanged and close to 1. The degree of branching of the isolated RG-I fractions was estimated at 0.33 to 0.65. The structural variability of the acidic fractions appeared not to be related to the RG-I backbone but possibly to the type and degree of substitution. These results might serve as a basis for developing chromatography conditions to contribute towards a better separation of mucilage polysaccharides.
Integument-specific transcriptional regulation in the mid-stage of flax seed development influences the release of mucilage and the seed oil content
2021, Cells
A small-scale fractionation pipeline for rapid analysis of seed mucilage characteristics
2020, Plant Methods
Cytological approaches combined with chemical analysis reveals the layered nature of flax mucilage
2019, Frontiers in Plant Science
MuSeeQ, a novel supervised image analysis tool for the simultaneous phenotyping of the soluble mucilage and seed morphometric parameters
2018, Plant Methods
Comparison of flax (Linum usitatissimum) and Salba-chia (Salvia hispanica L.) seeds on postprandial glycemia and satiety in healthy individuals: A randomized, controlled, crossover study
2017, European Journal of Clinical Nutrition
Research article
BCNU-induced gR2 DEFECT mediates S-glutathionylation of Complex I and respiratory uncoupling in myocardium
Biochemical Pharmacology, Volume 89, Issue 4, 2014, pp. 490-502
A deficiency of mitochondrial glutathione reductase (or GR2) is capable of adversely affecting the reduction of GSSG and increasing mitochondrial oxidative stress. BCNU [1,3-bis (2-chloroethyl)-1-nitrosourea] is an anticancer agent and known inhibitor of cytosolic GR ex vivo and in vivo. Here we tested the hypothesis that a BCNU-induced GR2 defect contributes to mitochondrial dysfunction and subsequent impairment of heart function. Intraperitoneal administration of BCNU (40mg/kg) specifically inhibited GR2 activity by 79.8±2.7% in the mitochondria of rat heart. However, BCNU treatment modestly enhanced the activities of mitochondrial Complex I and other ETC components. The cardiac function of BCNU-treated rats was analyzed by echocardiography, revealing a systolic dysfunction associated with decreased ejection fraction, decreased cardiac output, and an increase in left ventricular internal dimension and left ventricular volume in systole. The respiratory control index of isolated mitochondria from the myocardium was moderately decreased after BCNU treatment, whereas NADH-linked uncoupling of oxygen consumption was significantly enhanced. Extracellular flux analysis to measure the fatty acid oxidation of myocytes indicated a 20% enhancement after BCNU treatment. When the mitochondria were immunoblotted with antibodies against GSH and UCP3, both protein S-glutathionylation of Complex I and expression of UCP3 were significantly up-regulated. Overexpression of SOD2 in the myocardium significantly reversed BCNU-induced GR2 inhibition and mitochondrial impairment. In conclusion, BCNU-mediated cardiotoxicity is characterized by the GR2 deficiency that negatively regulates heart function by impairing mitochondrial integrity, increasing oxidative stress with Complex I S-glutathionylation, and enhancing uncoupling of mitochondrial respiration.
Research article
Osmotic stress alters the balance between organic and inorganic solutes in flax (Linum usitatissimum)
Journal of Plant Physiology, Volume 171, Issue 1, 2014, pp. 55-64
Flax (Linum usitatissimum) is grown for its oil and its fiber. This crop, cultivated in temperate regions, has seen a renewed interest due to the presence of abundant molecules of interest for many applications. Little information is available about the behavior of flax during osmotic stress; yet this is considered a major stress that causes significant yield losses in most crops. To control the presence of this stress better, flax behavior was investigated following the application of osmotic stress and the response was examined by applying increasing concentrations of PEG 8000. This resulted in the reorganization of 32 metabolites and 6 mineral ions in the leaves. The analysis of these two types of solute highlighted the contrasting behavior between a higher metabolite content (particularly fructose, glucose and proline) and a decrease in mineral ions (especially nitrate and potassium) following PEG treatment. However, this reorganization did not lead to a greater accumulation of solutes, with the total amount remaining unchanged in leaves during osmotic stress.
Research article
Identification of differentially expressed genes potentially involved in the tolerance of Lotus tenuis to long-term alkaline stress
Plant Physiology and Biochemistry, Volume 82, 2014, pp. 279-288
Soil alkalinity is one of the most serious agricultural problems limiting crop yields. The legume Lotus tenuis is an important forage acknowledged by its ability to naturally grow in alkaline soils. To gain insight into the molecular responses that are activated by alkalinity in L.tenuis plants, subtractive cDNA libraries were generated from leaves and roots of these plants. Total RNAs of non-stressed plants (pH 5.8; E.C. 1.2), and plants stressed by the addition of 10mM of NaHCO3 (pH 9.0; E.C. 1.9), were used as source of the driver and the tester samples, respectively. RNA samples were collected after 14 and 28 days of treatment. A total of 158 unigenes from leaves and 92 unigenes from roots were obtained and classified into 11 functional categories. Unigenes from these categories (4 for leaves and 8 for roots), that were related with nutrient metabolism and oxidative stress relief were selected, and their differential expression analyzed by qRT-PCR. These genes were found to be differentially expressed in a time dependent manner in L.tenuis during the alkaline stress application. Data generated from this study will contribute to the understanding of the general molecular mechanisms associated to plant tolerance under long-term alkaline stress in plants.
Research article
A multivariate approach for high throughput pectin profiling by combining glycan microarrays with monoclonal antibodies
Carbohydrate Research, Volume 409, 2015, pp. 41-47
Pectin–one of the most complex biomacromolecules in nature has been extensively studied using various techniques. This has been done so in an attempt to understand the chemical composition and conformation of pectin, whilst discovering and optimising new industrial applications of the polymer. For the last decade the emergence of glycan microarray technology has led to a growing capacity of acquiring simultaneous measurements related to various carbohydrate characteristics while generating large collections of data. Here we used a multivariate analysis approach in order to analyse a set of 359 pectin samples probed with 14 different monoclonal antibodies (mAbs). Principal component analysis (PCA) and partial least squares (PLS) regression were utilised to obtain the most optimal qualitative and quantitative information from the spotted microarrays. The potential use of microarray technology combined with chemometrics for the accurate determination of degree of methyl-esterification (DM) and degree of blockiness (DB) was assessed.
Research article
Seed mucilage effect on water uptake and germination in five species from the hyper-arid Arabian desert
Journal of Arid Environments, Volume 128, 2016, pp. 73-79
The effect of mucilage removal on germination percentages and velocity (Timson's index) was studied for five Arabian desert species (Lavandula subnuda, Lepidium aucheri, Boerhavia elegans, Plantago ciliata and Plantago amplexicaulis) under two photoperiods (0, 12h of light daily) and three thermoperiods (night/day temperatures of 15/25, 20/30 and 25/35°C). Mucilage presence increased water uptake in all species, and was associated with higher germination percentages in L.subnuda, B.elegans and P.ciliata, but not L.aucheri and P.amplexicaulis. Germination velocity response to mucilage presence was mixed, being increased in L.aucheri and reduced in L.subnuda. In all species germination was increased by light and affected by temperature, but species' response to temperature varied. Interactions of mucilage presence with temperature were more frequent than with light. Seed mucilage plays a role in germination regulation of these species, but the effects are species-specific. Mucilage presence inhibited germination at lower temperatures in L.subnuda and P.ciliata, at higher temperatures in B.elegans, and increased germination velocity but not percentage in L.aucheri. It had no influence on germination in P.amplexicaulis. The differences detected demonstrate as perhaps mucilage in seeds of some desert species serves also to other ecological purposes.
Research article
Polyamines as new cationic plasticizers for pectin-based edible films
Carbohydrate Polymers, Volume 153, 2016, pp. 222-228
Zeta potential and particle size were determined on pectin aqueous solutions as a function of pH and the effects of calcium ions, putrescine and spermidine on pectin film forming solutions and derived films were studied. Ca2+ and polyamines were found to differently influence pectin zeta potential as well as thickness and mechanical and barrier properties of pectin films prepared at pH 7.5 either in the presence or absence of the plasticizer glycerol. In particular, Ca2+ was found to increase film tensile strength and elongation at break only in the presence of glycerol and did not affect film thickness and permeability to both water vapor and CO2. Conversely, increasing polyamine concentrations progressively reduced film tensile strength and markedly enhanced film thickness, elongation at break and permeability to water vapor and CO2, both in the presence and absence of glycerol. Our findings indicate that polyamines give rise to a structural organization of the heteropolysaccharide different from that determined by calcium ions, previously described as “egg box” model, and suggest their possible application as plasticizers to produce pectin-based “bioplastics” with different features.
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