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Gene expression of stearoyl-ACP desaturase and delta12 fatty acid desaturase 2 is modulated during seed development of flax (Linum usitatissimum).

Flax's recent popularity in human and animal foods is mostly due to its desirable FA composition. Flax is an excellent source of omega-3 FA, which have been shown to have many health benefits. To date, little is known about the genetic and environmental factors that control the FA composition of flax seeds. To elucidate some of the important genetic components, reverse transcriptase (RT)-PCR and real-time PCR were used to determine the expression profiles of two key FA biosynthetic genes during seed development. Plants of flax cultivar AC McDuff were grown under field conditions, and RNA was extracted from ovaries and developing bolls collected from 2 d after anthesis (DAA) to maturity. Desaturation enzymes stearoyl-ACP desaturase (SAD) and delta12 FA desaturase 2 (FAD2) were both expressed in ovaries, and their expression was differentially modulated throughout seed development. SAD was most highly expressed in ovaries. Its expression quickly decreased until 4 DAA; this was followed by a slight peak at 8 DAA, only to return to relatively low levels of expression in maturing bolls, ranging from 2.1% to 4.5% relative to the level observed in ovaries. FAD2 expression displayed a different temporal pattern. While expression of FAD2 did decrease in the early stages of seed development, expression increased starting at 8 DAA, peaking at 16 DAA, when it was 158% relative to the level observed in ovaries. FAD2, which desaturates oleic acid (18:1cisdelta9) into linoleic acid (18:2cisdelta9,12), is therefore controlled at the transcription level. To relate enzyme expression with FA profile, GC was performed on the same subsamples used for RT-PCR and real-time PCR, and proportions of palmitic, stearic, oleic, linoleic, and linolenic acids were determined for the same developmental stages. Although FAD2 expression increased from 8 to 16 DAA, relative changes in linoleic acid (18:2cis delta9,12) were not observed. However, linolenic acid (ALA; alpha-18:3; 18:3cisdelta9,12,15) levels increased steadily, meaning that linoleic acid (18:2cisdelta9,12) is a transient substrate converted by FAD3 as quickly as it is produced by FAD2. Phenotypes are the result of genotypes, environment, and the interaction of the two. To evaluate the environmental impact on the production of FA in flax, FA profiles were assessed in a total of four environments (two locations, two years). Warm and dry environmental conditions resulted in lower levels of PUFA 18:2cisdelta9,12 and 18:3cisdelta9,12,15, and higher levels of 18:1 cisdelta9. FAD2 expression and/or activity may therefore be affected by the environment.

Base Sequence↗

Autoactive alleles of the flax L6 rust resistance gene induce non-race-specific rust resistance associated with the hypersensitive response.

L6 is a nucleotide binding site-leucine rich repeat (NBS-LRR) gene that confers race-specific resistance in flax (Linum usitatissimum) to strains of flax rust (Melampsora lini) that carry avirulence alleles of the AvrL567 gene but not to rust strains that carry only the virulence allele. Several mutant and recombinant forms of L6 were made that altered either the methionine-histidine-aspartate (MHD) motif conserved in the NBS domain of resistance proteins or exchanged the short domain C-terminal to the LRR region that is highly variable among L allele products. In transgenic flax some of these alleles are autoactive; they cause a gene dosage-dependent dwarf phenotype and constitutive expression of genes that are markers for the plant defense response. Their effects and penetrance ranged from extreme to mild in their degree of plant stunting, survival, and reproduction. Dwarf plants were also resistant to flax rust strains virulent to wild-type L6 plants, and this nonspecific resistance was associated with a hypersensitive response (HR) at the site of rust infection. The strongest autoactive allele, expressed in Arabidopsis from an ethanol-inducible promoter, gave rise to plant death dependent on the enhanced disease susceptibility 1 (EDS1) gene, which indicates that the mutant flax (Linaceae) L6 gene can signal cell death through a defined disease-resistance pathway in a different plant family (Brassicaceae).

Alleles↗

Enrichment and genotypic diversity of phlD-containing fluorescent Pseudomonas spp. in two soils after a century of wheat and flax monoculture.

Fluorescent Pseudomonas spp. producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) play a key role in the suppressiveness of some soils to take-all of wheat and other diseases caused by soilborne pathogens. Soils from side-by-side fields on the campus of North Dakota State University, Fargo, USA, which have undergone continuous wheat, continuous flax or crop rotation for over 100 years, were assayed for the presence of 2,4-DAPG producers. Flax and wheat monoculture, but not crop rotation, enriched for 2,4-DAPG producers, and population sizes of log 5.0 CFU g root(-1) or higher were detected in the rhizospheres of wheat and flax grown in the two monoculture soils. The composition of the genotypes enriched by the two crops differed. Four BOX-PCR genotypes (D, F, G, and J) and a new genotype (T) were detected among the 2,4-DAPG producers in the continuous flax soil, with F- and J-genotype isolates dominating (41 and 39% of the total, respectively). In contrast, two genotypes (D and I) were detected in the soil with continuous wheat, with D-genotype isolates comprising 77% of the total. In the crop-rotation soil, populations of 2,4-DAPG producers generally were below the detection limit, and only one genotype (J) was detected. Under growth-chamber and field conditions, D and I genotypes (enriched by wheat monoculture) colonized the wheat rhizosphere significantly better than isolates of other genotypes, while a J-genotype isolate colonized wheat and flax rhizospheres to the same extent. This study suggests that, over many years of monoculture, the crop species grown in a field enriches for genotypes of 2,4-DAPG producers from the reservoir of genotypes naturally present in the soil that are especially adapted to colonizing the rhizosphere of the crop grown.

Bacterial Proteins↗

Partial least squares regression calibration for determining wax content in processed flax fiber by near-infrared spectroscopy.

The quality of flax fiber in the textile industry is closely related to the wax content remaining on the fiber after the cleaning process. Extraction by organic solvents, which is currently used for determining wax content, is very time consuming and produces chemical waste. In this study, near-infrared (NIR) spectroscopy was used as a rapid analytical technique to develop models for wax content associated with flax fiber. Calibration samples (n=11) were prepared by manually mixing dewaxed fiber and isolated wax to provide a range of wax content from 0 to 5%. A total of fourteen flax fiber samples obtained after a cleaning process were used for prediction. Principal component analysis demonstrated that one principal component is enough to separate the flax fibers by their wax content. The most highly correlated wavelengths were 2312, 2352, 1732, and 1766 nm, in order of significance. Partial least squares models were developed with various chemometric preprocessing approaches to obtain the best model performance. Two models, one using the entire region (1100-2498 nm) and the other using the selected wavelengths, were developed and the accuracies compared. For the model using the entire region, the correlation coefficient (R2) between actual and predicted values was 0.996 and the standard error of prediction (RMSEP) was 0.289%. For the selected-wavelengths model, the R2 was 0.997 and RMSEP was 0.272%. The results suggested that NIR spectroscopy can be used to determine wax content in very clean flax fiber and that development of a low-cost device, using few wavelengths, should be possible.

Calibration↗

Effects of exposure to flax dust in Polish farmers: work-related symptoms and immunologic response to microbial antigens associated with dust.

Medical examinations were performed in a group of 51 Polish farmers heavily exposed to flax dust during harvesting and scutching (threshing) and in a group of 50 healthy urban dwellers not exposed to organic dusts (controls). The examinations included: interview concerning the occurrence of respiratory disorders and work-related symptoms, physical examination, X-ray examination of chest, lung function tests, oxymetric examinations, determination of the concentration of cytokines (IL-1alpha IL-6, TNFalpha) in blood serum and allergological tests with microbial antigens associated with organic dust, comprising: skin prick test with 4 antigens, agar-gel precipitation test with 12 antigens and test for specific inhibition of leukocyte migration with 4 antigens. As many as 32 farmers (62.7%) reported the occurrence of work-related symptoms during harvesting, transporting and scutching of flax. The most common complaint was general weakness reported by 15 farmers (29.4%), followed by headache reported by 14 (27.5%), blocking of the nose - by 11 (21.6%), dry cough, shivering, and eyes itching - each by 10 (19.8%), chest tightness and hoarseness - each by 9 (17.6%). No control subjects reported these work-related symptoms. The mean spirometric values in the examined group of farmers were within a normal range and did not show a significant post-shift decline. In contrast, a significant post-shift decline of oxymetric values was found among flax farmers. The farmers showed a frequency of the positive early skin reactions to environmental allergens in the range of 0-19.6%, a frequency of positive precipitin reactions in a range of 0-56.9%, and frequency of positive reactions of leukocyte migration inhibition in a range of 7.8-21.6%. The members of the control group responded to the majority of allergens with a significantly lower frequency of positive results compared to the farmers. Elevated concentrations of IL-1alpha and IL-6, but not TNFalpha, were found in blood sera of flax farmers. In conclusion, farmers engaged in harvesting and scutching of flax represent a group of elevated professional risk because of high incidence of work-related symptoms and high frequency of allergic reactions to bacteria and fungi associated with organic dust.

Adult↗

Exposure to airborne microorganisms, dust and endotoxin during flax scutching on farms.

Microbiological air sampling was performed on 5 flax farms located in eastern Poland. Air samples for determination of the concentrations of microorganisms, dust and endotoxin were collected in barns during machine scutching of flax stems by the farmers. The concentrations of mesophilic bacteria ranged from 203.5-698.8 x 10(3) cfu/m3, of Gram-negative bacteria from 27.2-123.4 x 10(3) cfu/m3, of thermophilic actinomycetes from 0.5-2.6 x 10(3) cfu/m3, and of fungi from 23.4-99.8 x 10(3) cfu/m3. The concentrations of total airborne microorganisms (bacteria + fungi) were within a range of 245.0-741.0 x 10(3) cfu/m3. The values of the respirable fraction of total airborne microflora on the examined farms were between 45.5-98.3%. Corynebacteria (irregular Gram-positive rods, mostly Corynebacterium spp.) were dominant at all sampling sites, forming 46.8-67.8% of the total airborne microflora. Among Gram-negative bacteria, the most numerous species was Pantoea agglomerans (synonyms: Erwinia herbicola, Enterobacter agglomerans), known to have strong endotoxic and allergenic properties. Among fungi, the allergenic species Alternaria alternata prevailed. Altogether, 25 species or genera of bacteria and 10 species or genera of fungi were identified in the farm air during flax scutching; of these, 11 and 6 species or genera respectively were reported as having allergenic and/or immunotoxic properties. The concentrations of airborne dust ranged within 43.7-648.1 mg/m3 (median 93.6 mg/m3), exceeding on all farms the Polish OEL value of 4 mg/m3. The concentrations of airborne endotoxin ranged within 16.9-172.1 microg/m3 (median 30.0 microg/m3), exceeding at all sampling sites the suggested OEL value of 0.2 microg/m). In conclusion, flax farmers performing machine scutching of flax could be exposed to large concentrations of airborne microorganisms, dust and endotoxin, posing a risk of work-related respiratory disease.

Agriculture↗

[Flax species polymorphism for isozyme and metabolic markers].

Genetic diversity of flax isozyme patterns of 6-phosphogluconate dehydrogenase, glutamate-oxaloacetate transaminase, and cytochrome-c-oxidase in leaves, as well as the level and the relative amounts of fatty acids in seed oil were studied in flax species. The isozyme loci examined were found to be polymorphic. It was shown that each of the flax species studied was characterized by strictly defined amounts and proportions of fatty acids, i.e., the fatty acid composition of the seed oil may be used as a species diagnostic trait. Our results suggest that all of the flax species studied have the same ancestor. Linum grandiflorum was shown to be a phylogenetic branch split at an early stage of the flax evolution.

Enzymes↗

Caffeoyl-coenzyme A 3-O-methyltransferase enzyme activity, protein and transcript accumulation in flax (Linum usitatissimum) stem during development.

Flax (Linum usitatissimum) is a commercially important fiber crop in Europe. Lignification of its phloem fibers, although weak, causes a decrease in their commercial quality. In flax, fiber lignin mainly consists of guaiacyl (G) units in contrast to the mixed guaiacyl-syringyl (G-S) lignin type occurring in xylem fibers. G lignins are reported as more condensed polymers due to a higher frequency of 5-5 linkages, whereas the deposition of syringyl end groups in lignins increases the proportion of alky-aryl ether linkages as beta-O-4-bonds. The type of linkages within a lignin polymer depends on the methylation of either the 3-hydroxyl groups or both 3-OH and 5-OH groups, which is controlled by two enzymes: caffeate 3-O-methyltransferase (COMT) and caffeoyl-coenzyme A 3-O-methyltransferase (CCoAOMT). First, we measured the in vitro activity of both OMTs in the flax stem tissues during stem development. CCoAOMT activity varied in the same way as COMT, i.e. increased gradually with stem maturity, from the top to the bottom of the stem, was maximum at the flowering stage and was lower, but still scorable, in the outer fiber-bearing tissues than in the xylem cells. In a second step, we focused our studies on the characterization of CCoAOMT in order to understand the implication of this enzyme in the lignification of flax fiber cells. CCoAOMT activity appeared to be associated with the accumulation of an acidic 33-kDa polypeptide identified as a CCoAOMT after immunological cross-reactivity with a poplar CCoAOMT and microsequencing. The differential accumulation of the CCoAOMT protein was confirmed by immunolocalization on tissue prints and correlated with that of the transcripts, suggesting a transcriptional regulation of CCoAOMT in the flax stem.

Journal Article↗

Effect of dietary flax oil and hypobaric hypoxia on right ventricular hypertrophy and ascites in broiler chickens.

1. The effect of dietary flax oil on growth rate, blood haemoglobin content, mortality and incidence of pulmonary hypertension and ascites in broilers at ambient pressure and at reduced atmospheric pressure was examined. 2. Birds were housed either in hypobaric chambers simulating 1000, 1500 or 2200 m altitude or in pens at ambient atmospheric pressure and fed on diets containing 100 g/kg added fat as either an animal/vegetable (A/V) blend or flax oil. 3. Birds raised under hypobaric conditions had a decreased growth rate and increased mortality, blood haemoglobin content, and incidence of pulmonary hypertension and ascites compared to the groups at normal atmospheric pressure. 4. Broilers fed on the diet containing flax oil showed no difference in growth rate or blood haemoglobin content compared to birds fed on the A/V fat diet raised at the same altitude. 5. Inclusion of flax oil in the diet decreased mortality and the incidence of ascites at 2200 m and pulmonary hypertension at 1500 m. 6. Flax oil may be an effective method of reducing ascites and pulmonary hypertension in broilers without affecting performance.

Altitude↗

Reducing atherogenic risk in hyperlipemic humans with flax seed supplementation: a preliminary report.

The effect on serum lipids of a flax seed supplement consisting of three slices of flax seed-containing bread and 15 g of ground flax seed was studied in 15 hyperlipemic subjects on long-term intake (800 IU/day) of vitamin E. The flax seed, which was high in alpha-linolenic acid and fiber, and which has been reported to lower serum cholesterol in elderly subjects, was provided in a 3-month feeding trial. Serum total and low-density lipoprotein cholesterol levels were reduced significantly; high-density lipoprotein cholesterol did not change during flax seed consumption. Thrombin-stimulated platelet aggregation decreased with the supplement. Serum lipid oxidation products decreased significantly during the washout period.

Adenosine Triphosphate↗

Role of histamine in the aetiology of byssinosis. II. Lung histamine concentrations in guinea pigs chronically exposed to cotton and flax dusts.

Data presented in this study support the finding that cotton and flax dusts contain agents which potentiate the formation or accumulation of histamine or both in the lungs of guinea pigs exposed to dust, and that such agents are present at much higher levels in cotton dust than in flax dust. The potentiating effect may be through the recruitment of mast cells into the lung. Both cotton and flax dusts contain methylating enzyme inhibitory agents, whereas cotton dust also contains agents that inhibit histaminase activity; flax dust contains agents potentiating histamine activity. These agents working together result in the accumulation or depletion of histamine observed in the different groups of animals exposed to either cotton or flax dust in this study.

Animals↗

Metabolizable energy and amino acid availability of full-fat seeds, meals, and oils of flax and canola.

The TME, true amino acid availability (TAAA), AME, and apparent amino acid availability (AAAA) were determined in full-fat seeds, meals, oils, and meal-oil mixtures of flax and canola using Single Comb White Leghorn roosters by the force feeding and total excreta collection assay. The metabolizable energy values were corrected to zero nitrogen balance to obtain AMEn and TMEn. The AMEn and TMEn contents of canola seed (4.46 and 4.56 kcal/g) were respectively higher (P < .05) than those of flax seed (3.75 and 3.75 kcal/g). Flax meal contains contents of AMEn (2.07 kcal/g) and TMEn (2.07 kcal/g) similar to those (1.98 and 2.09 kcal/g) of canola meal. There were no differences in AMEn and TMEn values between flax oil (8.10 and 8.28 kcal/g) and canola oil (8.25 and 8.46 kcal/g). No differences were observed among AME, AMEn, TME, and TMEn values within each test ingredient except canola meal: its TME value was higher (P < .05) than its AMEn value. The TAAA values were higher for full-fat seeds than for the meals and also higher for canola seed and meal than for flax seed and meal. The AAAA values, although lower than TAAA values, followed similar patterns as TAAA values. Both AAAA and TAAA values were higher when the ingredients were fed with a basal diet than when fed alone.

Amino Acids↗

Effect of medium osmotic potential on callus induction and shoot regeneration in flax anther culture.

Development of an efficient and cost-effective doubled haploid production system in flax (Linum usitatissimum L.) is the prerequisite for the application of doubled haploid technology in a practical breeding program. Pre-culture of anthers on a medium containing 15% sucrose for 2-7 days before transfer to the same medium containing 6% sucrose for a total of 28 days culture period significantly increased shoot regeneration for all four genotypes evaluated. Moreover, pre-culture of anthers on medium containing 15% sucrose for 2-7 days was sufficient to dramatically reduce the frequency of shoot regeneration from somatic tissues and thereby to increase the frequency of microspore-derived plants in flax anther culture. Furthermore, replacing 15% sucrose with 6% sucrose and 9% polyethylene glycol (PEG), or 3% sucrose and 12% PEG, in pre-culture medium did not significantly affect callus induction and shoot regeneration. The results indicate that sucrose may act as carbon/energy source as well as an osmotic regulator in flax anther culture. Sucrose as an osmotic regulator may be replaced by a non-metabolizable osmoticum: PEG. The implication of this study in flax anther culture and breeding is discussed.

Culture Media↗

Pinoresinol-lariciresinol reductase gene expression and secoisolariciresinol diglucoside accumulation in developing flax (Linum usitatissimum) seeds.

The transcription activity of the pinoresinol-lariciresinol reductase (PLR) gene of Linum usitatissimum (so-called LuPLR), a key gene in lignan synthesis, was studied by RT-PCR and promoter-reporter transgenesis. The promoter was found to drive transcription of a GUSint reporter gene in the seed coats during the flax seed development. This fitted well with the tissue localization monitored by semi-quantitative RT-PCR of LuPLR expression. Accumulation of the main flax lignan secoisolariciresinol diglucoside was coherent with LuPLR expression during seed development. This three-way approach demonstrated that the LuPLR gene is expressed in the seed coat of flax seeds, and that the synthesis of PLR enzyme occurs where flax main lignan is found stored in mature seeds, confirming its involvement in SDG synthesis.

Base Sequence↗

Haploid formation in maize, barley, flax, and potato.

The article is reviewing some significant features and issues in the process of haploid formation in two important monocotyledonous crop plants - maize and barley - and in two dicotyledonous plants - flax and potato. Exotic maize lines with higher androgenic response turned up as a good source for this heritable trait and this valuable trait can be incorporated into elite maize lines via crossing. Lots of attempts were devoted to identifying some cytological and/or morphological markers for androgenic response in maize microspore cultures. The "starlike" organization of the cytoplasm inside the induced maize microspores together with the enlarged size of induced microspores can be considered as morphological markers for androgenic response. In barley, microspores with rich cytoplasm that was of granular appearance with the nucleus located near the cell wall and with no visible vacuole had the largest survival rate and many of these cells continued in development and produced embryos. In flax, a dramatic increase of induction rate in anther cultures (up to 25%) was achieved when flax anthers were pretreated for 3 days at 4 degrees C and afterwards kept for 1 day at 35 degrees C. Also gynogenesis in flax has been reported already and complete plants were obtained. In potato microspore cultures, formation of two dissimilar cells indicated a strong polarization in the system and as a result of this polarization a prominent suspensor developed that persisted until the torpedo stage of the androgenic embryo. This was the first time the formation of a well developed suspensor was described in connection with androgenesis.

Flax↗

Lipids from flax fibers and their fate in alkaline pulping.

The chemical composition of lipids from bast fibers of flax (Linum usitatissimum), which are commonly used for high-quality paper pulp production, was thoroughly studied by gas chromatography-mass spectrometry. The main compounds identified were waxes, series of long chain n-fatty alcohols, n-aldehydes, n-fatty acids, and n-alkanes. Free and esterified sterols and triterpenols, steroid hydrocarbons, steroid and triterpenoid ketones, as well as sterol glycosides were also found in the flax bast fibers. On the other hand, the fate of these lipophilic compounds in alkaline pulping of flax fibers was investigated by analyzing two pulps obtained under distinct industrial cooking conditions. The results revealed that while waxes could be efficiently hydrolyzed during pulping depending on the alkali charge, most of the other lipophilic compounds present in flax fibers survived cooking and were present in the unbleached pulps.

Alcohols↗

Contrasting modes of evolution acting on the complex N locus for rust resistance in flax.

Three rust resistance specificities, N, N1 and N2, map to the complex N locus of flax. We used a degenerate PCR approach, with primers directed to the nucleotide binding site (NBS) domain characteristic of many plant resistance genes, to isolate resistance gene analogs (RGAs) from flax. One RGA clone detected RFLPs co-segregating with alleles of the N locus. With this probe we isolated four related genes that occur within a 30kbp region and encode proteins with NBS and leucine-rich repeat (LRR) domains and N-terminal Toll/Interleukin-1 Receptor homology (TIR) domains. One of these four genes was identified as the N resistance gene by sequence analysis of three mutant alleles and by transgenic expression. We isolated homologous genes from two flax lines containing the N1 or N2 specificities and from flax lines carrying no N locus resistance specificities. Analysis of shared polymorphisms among this set of 18 N locus sequences revealed three groups of genes with independent lineages. Sequence exchanges have only occurred between genes within each group, but not between groups. Two of the groups contain only one sequence from each haplotype and probably represent orthologous genes. However, the third group contains two genes from each haplotype. We suggest that the re-assortment of variation by recombination/gene conversion at this locus is limited by the degree of sequence identity between genes.

Alleles↗

ESTs from the fibre-bearing stem tissues of flax (Linum usitatissimum L.): expression analyses of sequences related to cell wall development.

In order to learn more about the diversity of genes expressed during flax fibre cell wall formation, expressed sequence tags (ESTs) were obtained from a cDNA library derived from the outer fibre-bearing tissues of flax (Linum usitatissimum) stems (cv Hermes) harvested at the mid-flowering stage. After elimination of vector and unreadable sequences, 927 ESTs were grouped into 67 clusters and 754 singletons. The flax ESTs have been submitted to the dbEST and GenBank databases with the accession numbers 25939634 - 25940560 (dbEST) and CV478070 - CV478996 (GenBank). Functional analysis allowed the grouping of ESTs into 13 functional categories and revealed that 62 % of ESTs were similar to known sequences, while 12.4 % of ESTs presented no similarity to any known sequences and 25.6 % of ESTs corresponded to proteins of unknown function. The most highly expressed transcripts belonged to four functional categories: protein maturation and metabolism (31 ESTs), signalling (22 ESTs), the cell wall (21 ESTs) and photosynthesis (19 ESTs). 4.4 % (41) of the total ESTs were potentially related to cell wall formation and maturation. The most highly expressed cell wall EST (15 ESTs) corresponded to a beta-xylosidase gene--potentially involved in cell wall remodelling during growth and development. Other cell wall-related ESTs corresponded to cellulose synthase, xyloglucan endotranglucosylase/hydrolase (XTH), beta-galactosidases, and peroxidases. The expression patterns of different cell wall-related ESTs were determined at different developmental stages in flax plants grown under different field conditions. The potential roles of gene products associated with cell wall related ESTs in fibre cell wall development is discussed.

Cell Wall↗