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PubMed1992

The flax ribosomal RNA-encoding genes are arranged in tandem at a single locus interspersed by 'non-rDNA' sequences.

The ribosomal RNA (rRNA)-encoding genes (rDNA) in flax, estimated to be present in about 2400 copies per diploid nucleus, have been reported as a single homogeneous repeat unit of 8.6 kb. In situ hybridization analysis indicated that these genes were located at a single site on one pair of chromosomes. However, an analysis of a flax variety, CI 1303, has revealed heterogeneity in the intergenic spacer of the rDNA repeat unit. A genetic analysis of rDNA inheritance in two flax lines, Stormont Cirrus and CI 1303, has again supported the observation that there is a single rDNA locus in this plant species. Screening of four different genomic libraries made in methylation-sensitive and -insensitive systems, and the analysis of 40 phage clones, demonstrate a much higher number than that expected of junctions between rDNA and non-rDNA. Direct evidence of rRNA-encoding genes being present in tandem comes from a few phage clones that contain more than two rDNA repeats. The evidence presented here indicates that rDNA, although present at a single locus in tandem arrays, may be interrupted frequently by other non-rDNA sequences, thus giving rise to questions about their organization into long tandem arrays.

Blotting, Southern↗
PubMed1975

Seasonal exposure to dust in flax processing in Egypt.

Previous evidence suggested that interruption of worker's exposure to flax dust may lead to severe symptoms of byssinosis on their return to work. In the present study, the prevalence and severity of byssinosis was studied in a sample of flax workers (n=577) who had been exposed to dust for six months each year. Byssinosis prevailed in 36.9% of them, and 32.3% of them had their FEV 1.0 sec reduced 10% at the end of the first morning work period (4 to 6 hours) of the week. Both syndromes were higher among seasonal workers than what would be predicted if they were pemanently exposed to flax dust. A hypothesis has been presented to interpret this finding.

Air Pollution↗
PubMed1996

Cell-Wall Polysaccharides of Developing Flax Plants.

Flax (Linum usitatissimum L.) fibers originate from procambial cells of the protophloem and develop in cortical bundles that encircle the vascular cylinder. We determined the polysaccharide composition of the cell walls from various organs of the developing flax plant, from fiber-rich strips peeled from the stem, and from the xylem. Ammonium oxalate-soluble polysaccharides from all tissues contained 5-linked arabinans with low degrees of branching, rhamnogalacturonans, and polygalacturonic acid. The fiber-rich peels contained, in addition, substantial amounts of a buffer-soluble, 4-linked galactan branched at the 0-2 and 0-3 positions with nonreducing terminal-galactosyl units. The cross-linking glycans from all tissues were (fucogalacto)xyloglucan, typical of type-I cell walls, xylans containing (1->)-[beta]-D-xylosyl units branched exclusively at the xylosyl O-2 with t-(4-O-methyl)-glucosyluronic acid units, and (galacto)glucomannans. Tissues containing predominantly primary cell wall contained a larger proportion of xyloglucan. The xylem cells were composed of about 60% 4-xylans, 32% cellulose, and small amounts of pectin and the other cross-linking polysaccharides. The noncellulosic polysaccharides of flax exhibit an uncommonly low degree of branching compared to similar polysaccharides from other flowering plants. Although the relative abundance of the various noncellulosic polysaccharides varies widely among the different cell types, the linkage structure and degree of branching of several of the noncellulosic polysaccharides are invariant.

Journal Article↗
PubMed1998

Inhibition of wound-induced accumulation of allene oxide synthase transcripts in flax leaves by aspirin and salicylic acid

Allene oxide synthase (AOS) mediates the conversion of lipoxygenase-derived fatty acid hydroperoxides to unstable allene epoxides, which supply the precursors for the synthesis of the phytohormone jasmonic acid (JA). In this study the characterization of AOS gene expression in flax (Linum usitatissimum) is reported. AOS was constitutively expressed in different organs of flax plants. Additionally, AOS gene expression was enhanced after mechanical wounding in both the directly damaged leaves and in the systemic tissue located distal to the treated leaves. This wound-induced accumulation of AOS required the de novo biosynthesis of other unknown proteins involved in the signaling pathway modulating wound-induced AOS gene expression. Furthermore, the wound-induced AOS mRNA accumulation was correlated with the increase in the levels of JA. Both JA and its precursor, 12-oxo-phytodienoic acid, activated AOS gene expression in a dose-dependent manner. Thus, JA could activate its own biosynthetic pathway in flax leaves. Moreover, neither salicylic acid (SA) nor aspirin influenced AOS enzymatic activity. It is interesting that pretreatment with SA or aspirin inhibited wound-induced accumulation of AOS transcripts. These results suggest that a potent inhibition of JA biosynthetic capacity in leaves can be affected by SA or aspirin at the level of AOS gene expression.

Journal Article↗
PubMed1995

Expression of a Flax Allene Oxide Synthase cDNA Leads to Increased Endogenous Jasmonic Acid (JA) Levels in Transgenic Potato Plants but Not to a Corresponding Activation of JA-Responding Genes.

Both jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA), are thought to be significant components of the signaling pathway regulating the expression of plant defense genes in response to various stresses. JA and MeJA are plant lipid derivatives synthesized from [alpha]-linolenic acid by a lipoxygenase-mediated oxygenation leading to 13-hydroperoxylinolenic acid, which is subsequently transformed by the action of allene oxide synthase (AOS) and additional modification steps. AOS converts lipoxygenase-derived fatty acid hydroperoxide to allene epoxide, which is the precursor for JA formation. Overexpression of flax AOS cDNA under the regulation of the cauliflower mosaic virus 35S promoter in transgenic potato plants led to an increase in the endogenous level of JA. Transgenic plants had six- to 12-fold higher levels of JA than the nontransformed plants. Increased levels of JA have been observed when potato and tomato plants are mechanically wounded. Under these conditions, the proteinase inhibitor II (pin2) genes are expressed in the leaves. Despite the fact that the transgenic plants had levels of JA similar to those found in nontransgenic wounded plants, pin2 genes were not constitutively expressed in the leaves of these plants. Transgenic plants with increased levels of JA did not show changes in water state or in the expression of water stress-responsive genes. Furthermore, the transgenic plants overexpressing the flax AOS gene, and containing elevated levels of JA, responded to wounding or water stress by a further increase in JA and by activating the expression of either wound- or water stress-inducible genes. Protein gel blot analysis demonstrated that the flax-derived AOS protein accumulated in the chloroplasts of the transgenic plants.

Journal Article↗
PubMed1975

Dust exposure in manual flax processing in Egypt.

Manual flax processing originated in Egypt in 2 000 BC. In the present study a representative sample of the workers involved in this trade, where flax is processed in small workshops or homes, was examined, and their dust exposure was evaluated. The study showed that workers handling and processing flax are exposed to high concentrations of dust; the levels of dust at hackling and combing are considerably higher than at batting and spinning. Byssinosis prevailed in 22-9% of the examined workers, and 18-4% of them had their forced expiratory volume in one second reduced by more than 10% at the end of the first morning work period (4 hours) of the week. Both the rates and the grades of these syndromes increased with duration of exposure. Smoking appeared to be one of the important contributory factors in the production of byssinosis. The relationship between dust concentration and prevalence of byssinosis seems to be curvilinear.

Adult↗
PubMed1979

HLA antigen frequencies in flax byssinosis patients.

Not all workers exposed to flax dust contract byssinosis. It is not known what determines susceptibility or insusceptibility. This study is an attempt to establish whether the incidence of histocompatibility antigens is involved in susceptibility to the disease. Forty patients suffering from flax byssinosis were tissue-typed for HLA-A and -B antigens. HLA-B27 was significantly more common in the patients (22.5%) than in the controls (5.5%); P = 0.029 after correction for the number of antigens compared. HLA-A11 was present in twelve patients (30%) compared with 14% in the controls; after correction for the number of comparisons, this is not a statistically significant increase. Because HLA-B27, though significantly more common in flax byssinosis, is not necessary for its occurrence (77.5% of our patients did not have it), it is possible that the increase in the frequency of HLA-B27 is attributable to an association with other genes, perhaps those regulating the immune response or coding for antigens at other HLA loci.

Adult↗
PubMed1988

Low prevalence of byssinotic symptoms in 12 flax scutching mills in Normandy, France.

The concentrations of airborne dust and bacteria were determined in 12 flax scutching mills and in two milk processing plants in Normandy, France. A total of 308 of 340 flax workers and 111 of 113 milk processors volunteered to answer a respiratory questionnaire. Personal exposure to airborne dust in the scutching mills varied from 22.2 mg/m3 to 144 mg/m3 and areal concentrations from 8.92 mg/m3 to 47.1 mg/m3. The concentration of Gram negative bacteria ranged from 3970 (colony forming units) cfu/m3 to 67,900 cfu/m3 and that of total bacteria from 12,900 cfu/m3 to more than 600,000 cfu/m3. In all, 20% of the flax scutchers were found, on the basis of the questionnaire, to suffer from persistent cough and 25% from chronic phlegm production. The corresponding figures among milk processors were 3.6% and 4.5%. Unexpectedly, only 12.5% of the scutchers appeared to suffer from byssinotic symptoms even though they were heavily exposed to airborne dust and bacteria. The low prevalence of byssinosis might be due to self selection of the workforce or a relatively low concentration of the causative agent despite high airborne contamination.

Air Microbiology↗
PubMed1991

Effects of feeding flax and two types of sunflower seeds on fatty acid compositions of yolk lipid classes.

Single Comb White Leghorn laying hens were fed diets high in oleic, linolenic, or linoleic acid prepared by incorporation of high oleic acid sunflower seed (HOAS), full-fat flax seed (FLAX), or regular high linoleic acid sunflower seed (HLAS), respectively, to investigate the effects of dietary fats on the fatty acid compositions of major lipid classes of chicken eggs. Egg production, Haugh units, specific gravity, and yolk total lipid content were measured. After 3 wk of feeding, the fatty acid compositions of yolk total lipids, triglycerides, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) were measured by gas chromatography. Dietary treatments had no effect on egg production, Haugh units, specific gravity, or yolk total lipid content. Feeding HOAS increased yolk oleic acid by 17%, and the change was only in triglycerides. The increases of yolk linoleic and arachidonic acids upon HLAS feeding were distributed evenly among triglycerides and PC, with moderate effect in the PE fraction. The enrichment of linolenic acid in eggs from the FLAX regime was mainly in triglycerides. The longer chain n-3 fatty acids, such as eicosapentaenoic, dososapentaenoic, and docosahexaenoic acids, were deposited exclusively in phospholipids, particularly in PE. The contents of the longer chain n-3 fatty acids in PE were three to seven times those in PC, indicating a preferential incorporation of these fatty acids into PE.

Animal Feed↗
PubMed1991

[Long-term consequences of lung injuries in flax scutchers].

A female patient, 60 years old, had been working as a flax scutcher for 20 years. Sectional investigation showed fissural thin-walled caverns in the superior lobe of the lung. Histologic investigation revealed granulomas of epithelioid and lymphoid cells in the lungs, pleura, spleen, and silicon dioxide crystals in the lung tissue. The clinical picture resulted from a combined action of flax dust particles and silicon dioxide, and was similar to those of allergic exogenous alveolitis and late stages of silicosis, which attributed it to the occupational diseases of flax scutchers.

Agricultural Workers' Diseases↗
PubMed2003

Regeneration of flax ( Linum usitatissimum L.) plants from anther culture and somatic tissue with increased resistance to Fusarium oxysporum.

The aim of this study was to establish a protocol for the efficient production of flax plants of microspore origin. The results were compared to those obtained for plants regenerated from somatic explants from hypocotyls, cotyledons, leaves, stems and roots. All the plants obtained during the experiments were regenerated from callus that was grown for periods from a few weeks to a few months before the regeneration was achieved. Anther cultures were less effective in plant regeneration than somatic cell cultures. However, regenerants derived from anther cells showed valuable breeding features, including increased resistance to fungal wilt. The age of the donor plants and the season they grew in had a noticeable effect on their anther callusing and subsequent plant regeneration. Low temperature had a negative effect and dark pre-treatment a positive effect on callusing and plant regeneration. Different media were most effective for callus induction, shoot induction and rooting. For callus induction two carbon sources (2.5% sucrose and 2.5% glucose) were most effective; for shoots, only sucrose at lower concentration (2%) was effective. Rooting was most efficient in 1% sucrose and reduced (50%) mineral concentration in the medium. It was found that the length of in vitro cultivation significantly increases the ploidy and affects such features as regenerant morphological characteristics, petal colour, and resistance to Fusarium oxysporum-induced fungal wilt. The established plant regeneration system provides a basis for the creation of transgenic flax.

Culture Techniques↗
PubMed2000

A (1-->3,6)-beta-d-galactosyl epitope containing uronic acids associated with bioactive pectins occurs in discrete cell wall domains in hypocotyl and root tissues of flax seedlings.

We have used a well-characterized antibody specific for an epitope consisting of (1-->3,6)-beta-d-galactosyl residues with terminal glucuronic or 4-O-methylglucuronic acids of a bioactive pectin and immunocytochemistry to investigate its secretion and wall distribution in the hypocotyl and root tissues of flax seedlings. Our results show that this antigenic epitope is associated with flax pectins and is expressed by all the cells of the hypocotyl and root tissues. In the hypocotyl, it is abundant in the primary wall of epidermal cells as well as in the secondary wall of fiber cells, and is relatively less abundant in parenchyma cell walls. In contrast, the epitope is not detected in the middle lamellae and cell junction regions. In the root tip cells, immunogold electron microscopy shows that the cell walls of peripheral, columella, meristematic, cortical, and epidermal cells contain significant amounts of this epitope and that the distribution patterns are distinct. Together, these findings show that the antigenic epitope occurs in discrete domains of the wall implying a strict spatial regulation of the epitope-containing molecules. The results also show that, in root cells, the epitope is present within Golgi cisternae and is predominantly assembled in the trans and the trans-Golgi network compartments.

Antibodies↗
PubMed2005

A rust-inducible gene from flax (fis1) is involved in proline catabolism.

A gene fis1 from flax (Linum usitatissimum), which is induced in mesophyll cells at the site of rust (Melampsora lini) infection, is also expressed in vascular tissue, particularly in floral structures of healthy plants. This paper reports that the promoter controlling this expression is contained within 282 bp 5' to the coding region and that fis1 gene induction is specifically by the rust pathogen and not by other fungal pathogens or by wounding. The fis1 gene has 73% homology with an Arabidopsis gene which encodes delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDH) which is a part of the proline degradation pathway. Transgenic flax plants that either over-express fis1 or show reduced fis1 expression due to RNA-mediated gene silencing have an unaltered morphology. However, plants with reduced fis1 expression have markedly increased sensitivity to exogenous proline and show alteration in epidermal cell morphology, callose deposition and the production of hydrogen peroxide during proline-induced death. These lines, which show a biologically significant level of fis1 suppression, have an unaltered reaction to either virulent or avirulent rust infections, as do fis1 over-expression lines. These data indicate that the fis1 gene plays a role in proline metabolism and most likely encodes for a P5CDH enzyme. However, the precise role of fis1 and P5C catabolism in the development of rust disease remains unclear.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed2005

Secondary cell-wall assembly in flax phloem fibres: role of galactans.

Non-lignified fibre cells (named gelatinous fibres) are present in tension wood and the stems of fibre crops (such as flax and hemp). These cells develop a very thick S2 layer within the secondary cell wall, which is characterised by (1) cellulose microfibrils largely parallel to the longitudinal axis of the cell, and (2) a high proportion of galactose-containing polymers among the non-cellulosic polysaccharides. In this review, we focus on the role of these polymers in the assembly of gelatinous fibres of flax. At the different stages of fibre development, we analyse in detail data based on sugar composition, linkages of pectic polymers, and immunolocalisation of the beta-(1-->4)-galactans. These data indicate that high molecular-mass gelatinous galactans accumulate in specialised Golgi-derived vesicles during fibre cell-wall thickening. They consist of RG-I-like polymers with side chains of beta-(1-->4)-linked galactose. Most of them are short, but there are also long chains containing up to 28 galactosyl residues. At fibre maturity, two types of cross-linked galactans are identified, a C-L structure that resembles the part of soluble galactan with long side chains and a C-S structure with short chains. Different possibilities for soluble galactan to give rise to C-L and C-S are analysed. In addition, we discuss the prospect for the soluble galactan in preventing the newly formed cellulose chains from completing immediate crystallisation. This leads to a hypothesis that firstly the secretion of soluble galactans plays a role in the axial orientation of cellulose microfibrils, and secondly the remodelling and cross-linking of pectic galactans are linked to the dehydration and the assembly of S2 layer.

Cell Wall↗
PubMed2005

Intrusive growth of flax phloem fibers is of intercalary type.

Flax (Linum usitatissimum L.) phloem fibers elongate considerably during their development and intrude between existing cells. We questioned whether fiber elongation is caused by cell tip growth or intercalary growth. Cells with tip growth are characterized by having two specific zones of cytoplasm in the cell tip, one with vesicles and no large organelles at the very tip and one with various organelles amongst others longitudinally arranged cortical microtubules in the subapex. Such zones were not observed in elongating flax fibers. Instead, organelles moved into the very tip region, and cortical microtubules showed transversal and helical configurations as known for cells growing in intercalary way. In addition, pulse-chase experiments with Calcofluor White resulted in a spotted fluorescence in the cell wall all over the length of the fiber. Therefore, it is concluded that fiber elongation is not achieved by tip growth but by intercalary growth. The intrusively growing fiber is a coenocytic cell that has no plasmodesmata, making the fibers a symplastically isolated domain within the stem.

Cell Enlargement↗
PubMed2000

Identification and partial characterization of proteins and proteoglycans encrusting the secondary cell walls of flax fibres.

Four proteins were isolated from depectinised elementary fibres of flax (Linum usitatissimum L.), using either alkali or cellulase digestion treatments. All the four proteins were characterized by a deficiency or low contents of hydroxyproline and by high levels of glutamic acid/glutamine and/or aspartic acid/asparagine. The two proteoglycans solubilized with cellulase strongly reacted with beta-glucosyl Yariv reagent but not with alpha-glucosyl Yariv reagent and contained appreciable amounts of alanine, glycine, serine and threonine, suggesting a relationship with cell wall hydroxyproline-deficient arabinogalactan-proteins. The two alkali-extracted proteins did not show any reaction with beta-glucosyl Yariv dye. Due to the harsh treatment, they might only partially represent the original proteins. Due to its high level of glycine (41%), one of these proteins might be classified as a glycine-rich protein. The latter polypeptide, of low molecular molar mass, contained 14.6% leucine and might consist of a domain related to leucine-rich proteins. The data show that these proteins and arabinogalactan-protein-like proteoglycans were strongly associated with the secondary walls of flax fibres. Their presence in small amounts (0.1-0.4%), raises the problem of their putative structural role.

Amino Acids↗
PubMed2001

Solubilization of rhamnogalacturonan I galactosyltransfrases from membranes of a flax cell suspension.

Galactosyltransferases (GalTs), capable of transferring a galactosyl residue from UDP-galactose (UDP-Gal) to polysaccharide acceptor, were solubilized from flax (Linum usitatissimum L.) membranes using 0.5% CHAPS. The observed requirement for a rhamnogalacturonan I (RG-I) exogenous substrate to stimulate the solubilized GalT activity provided the first evidence for the presence of RG-I GalT activities in flax cells. An assay to measure specifically the products of this RG-I GalT activity was designed, based on size-exclusion chromatography. Labelled products were characterized as an RG-I polymer by using purified RG-I hydrolase or lyase. At pH 8 and in the presence of 5 mM CaCl2, beta-D-galactosyl residues were specifically transferred onto RG-I branches of short beta-(1 --> 4)-D-galactan side chains. These side chains were liable to hydrolysis by beta-galactosidase and endo-beta-(1 --> 4)-D-galactanase. The RG-I GalT had a temperature optimum of 30 degrees C. an apparent Km for UDP-Gal and exogenous RG-I substrate of 460 +/- 40 microM and 1.1 +/- 0.1 mg ml(-1) respectively, and a Vmax of 3.0 +/- 0.5 pkat mg(-1) protein.

Cell Membrane↗
PubMed2005

Methods for obtaining neutral and acid oligosaccharides from flax pectins.

Esterified acid soluble pectins from flax (Linun usitatissimum L.) were degraded either with HCl or pectin lyase. Centrifugation and 2-propanol precipitation led to the isolation of two low molecular weight polygalacturonates after acid hydrolysis of pectins. However, after pectin lyase digestion and purification by size-exclusion HPLC, (1)H NMR analyses indicated that acetylated hairy regions, large methylated and acetylated oligogalacturonides together with small unsubstituted oligogalacturonides were produced. Thus, in a few steps, a panel of substituted neutral and acidic oligosaccharides was produced from a raw plant material. Such oligosaccharides could be useful for further fractionations such as chemical saponification and enzymatic removal of neutral sugar chains from the hairy regions. The procedures used for pectin extraction, for degradation, and for the purification of fragments seem appropriate for large-scale production of biologically active oligosaccharides from flax.

Acetylation↗