Nanoparticles enhances the salinity toxicity tolerance in Linum usitatissimum L. by modulating the antioxidative enzymes, photosynthetic efficiency, redox status and cellular damage.

The contribution of nanoparticles (NPs) in physiology of the plants became the new area of interest for the physiologists; as it is very much cost effective compared to the phytohormones. Our present investigation was also based on this interest in which the same doses (50 mg/L) of four different NPs were sprayed on stressed and non-stressed foliage. The experiment was conducted to assess the impact of four NPs viz., zinc oxide (ZnO), silicon dioxide (SiO2), titanium dioxide (TiO2), and ferric oxide (Fe2O3) on the morphology and physiology of linseed in the presence of sodium chloride (NaCl). Plants responded positively to all the treated NPs and improved the growth, carbon and nutrient assimilation, while salt stress increased the content of proline, hydrogen peroxide and superoxide anion. Application of NPs over the stressed plants further increased the antioxidant enzymatic system and other physiochemical reactions. Results indicate that application of NPs increased the growth and physiology of the plant and also increased the salt tolerance capacity of the plant.

Loci harboring genes with important role in drought and related abiotic stress responses in flax revealed by multiple GWAS models.

KEY MESSAGE: QTNs associated with drought tolerance traits and indices were identified in a flax mini-core collection through multiple GWAS models and phenotyping at multiple locations under irrigated and non-irrigated field conditions. Drought is a critical phenomenon challenging today's agricultural sector. Crop varieties adapted to moisture deficit are becoming vital. Flax can be greatly affected by limiting moisture conditions, especially during the early development and reproductive stages. Here, a mini-core collection comprising genotypes from more than 20 major growing countries was evaluated for 11 drought-related traits in irrigated and non-irrigated fields for 3 years. Heritability of the traits ranged from 44.7 to 86%. Six of the 11 traits showed significant phenotypic difference between irrigated and non-irrigated conditions. A genome-wide association study (GWAS) was performed for these six traits and their corresponding stress indices based on 106 genotypes and 12,316 single nucleotide polymorphisms (SNPs) using six multi-locus and one single-locus models. The SNPs were then assigned to 8050 linkage disequilibrium (LD) blocks to which a restricted two-stage multi-locus multi-allele GWAS was applied. A total of 144 quantitative trait nucleotides (QTNs) and 13 LD blocks were associated with at least one trait or stress index. Of these, 16 explained more than 15% of the genetic variance. Most large-effect QTN loci harbored gene(s) previously predicted to play role(s) in the associated traits. Genes mediating responses to abiotic stresses resided at loci associated with stress indices. Flax genes Lus10009480 and Lus10030150 that are predicted to encode WAX INDUCER1 and STRESS-ASSOCIATED PROTEIN (SAP), respectively, are among the important candidates detected. Accessions with multiple favorable alleles outperformed others for grain yield, thousand seed weight and fiber/biomass in non-irrigated conditions, suggesting their potential usefulness in breeding and genomic selection.

Experimental evaluation of stiffness predictions of multiaxial flax fibre composites by classical laminate theory.

Despite the good mechanical properties of natural fibre composites, their use in load-bearing components is still limited, which may be due to lack of knowledge and confidence in calculating the performance of the composites by mechanical models. The present study is providing an experimental evaluation of stiffness predictions of multiaxial flax fibre composite by classical laminate theory (CLT). The experimental base is (i) multiaxial flax fibre composites fabricated with two types of biaxial non-crimp fabrics, having a nominal yarn orientation of ±45°, and (ii) uniaxial flax fibre composites fabricated with the same flax yarn as used in the fabrics. The fabricated composites are characterised by volumetric composition, yarn orientation and tensile properties. A fast and easy operational Fast Fibre Orientation (FFO) method is developed to determine the actual yarn orientation in fabrics and composites. It is demonstrated that the FFO method is a robust method, giving repeatable results for yarn orientations, and it can be used both on fabrics and composites. CLT predictions of stiffness of the multiaxial flax fibre composites are shown to be in good agreement with the measured stiffnesses of the composites in three testing directions (0°, 45°, and 90°). The use of the actual yarn orientations measured by the FFO method, instead of the nominal yarn orientations of ±45°, is shown to result in improved CLT predictions of stiffness with a mean deviation between predictions and measurements on 0.2 GPa. Altogether, it is demonstrated that stiffness of multiaxial flax fibre composites can be accurately predicted by CLT, without any fitting constants, based on independently determined stiffness parameters of the related uniaxial flax fibre composite, and based on measured yarn orientations in the flax fibre fabric.

Is the protein profile of pig Longissimus dorsi affected by gender and diet?

The impact of gender and diet on the proteome of Longissimus dorsi was addressed by 2D-PAGE analysis of male and female pigs, fed with a barley-based control diet and a diet enriched with extruded linseed and plant extracts. No statistically significant difference in protein number between female and male samples was found. Furthermore, PCA excluded gender-dependent protein clusters. For both the control and enriched diet, several spots exhibited at least a 1.5-fold intensity difference, but none showed a statistically relevant variation. Protein profiles PCA for both diets indicated that the first two principal components account up to 47% of total variance, with two diet-dependent separated clusters. Among 176 common spots, 29 exhibited >1.5 fold change, mostly more abundant in the control diet. PMF identified 14 distinct proteins, including myofibrillar proteins, glycolytic enzymes and myoglobin, thus suggesting a diet-dependent meat quality. A statistically significant increase in carbonylated proteins of enriched diet samples was detected using the 2,4-dinitrophenylhydrazine method but not using fluorescein-5-thiosemicarbazide-labeled bands. ROS induction and DNA oxidative damage, detected in a human cell line exposed to digested meat from both diets, further support the notion that the enriched diet does not protect against oxidative stress. SIGNIFICANCE: The comparison of the protein profile of female and male Longissimus dorsi from pigs fed by a control diet and a diet enriched with polyphenols, indicate no gender effect, whereas diet affects the abundance of several proteins, possibly linked to meat quality. Protein carbonylation was statistically higher in meat from the enriched diet, suggesting that polyphenols at the concentration present in the diet did not exert a protective effect against oxidation.

RNAi-mediated silencing of pinoresinol lariciresinol reductase in Linum album hairy roots alters the phenolic accumulation in response to fungal elicitor.

Lignans are diphenolic compounds produced in plants via coupling of two coniferyl alcohol molecules with the aid of a dirigent protein to form pinoresinol (PINO). The latter is reduced via lariciresinol (LARI) to secoisolariciresinol by the bifunctional pinoresinol-lariciresinol reductase (PLR). In this study, we clarified the consequences of altered lignan biosynthesis on amino acids, phenolics compounds and lignin in the hairy roots of Linum album with an ihpRNAi construct to silence PLR gene expression. Down-regulation of PLR-La1 resulted in up to an 8.3 and 3.3-time increased PINO and LARI content respectively, and reduced levels of podophyllotoxin (PTOX) and 6-methoxy podophyllotoxin (6-MPTOX). By Suppression of PLR expression, the metabolites belonging to shikimate and phenylpropanoid pathways are conducted to phenolic compounds and lignin accumulations. Although PINO and LARI were induced in response to fungal elicitor, the accumulation of PTOX and 6-MPTOX did not occur in PLR down-regulated roots. Our result also demonstrated variation in amino acids, phenolic compounds and lignin levels in presence of the fungal elicitation in PLR down regulated-roots. This data assert the accumulation of aryltetralin lignans in interactions with plant pathogens by PLR activity and the importance this enzyme for defense against pathogens in L. album.

Autonomous self-fertilization in Linum sulcatum, a native annual with a previously unknown mating system.

The mating systems of wild plant populations have profound effects on their genetic structure and evolution, yet remain unknown or incompletely described for many species. One such species, the herbaceous native annual Linum sulcatum Riddell (Linaceae), is thought to be self-compatible, but there has been no experimental evidence to date to support this claim. To assess the breeding system of this species, seeds were collected from wild populations and reared in a controlled environment. Floral manipulations and controlled pollinations were conducted to determine the degree of self-compatibility of this species and to distinguish between autonomous and facilitated modes of selfing. Additional controlled within- and between-population crosses were conducted to determine the relative degree to which this species can outcross. This study showed that self-fertilization was highly successful and can occur autonomously. In contrast, outcrossing success, both within and between populations, was very limited, suggesting this species may exhibit an extreme degree of cross-incompatibility. A pollen tube growth experiment showed that self-pollination resulted in the formation of more pollen tubes relative to cross-pollination and that complete pollen tube growth can occur less than 2 h following self-pollination. This information is relevant to the future persistence of this species, as much of its remaining habitat is distributed among small, highly fragmented patches subjected to current and future environmental stressors.

Supplemental flaxseed modulates ovarian functions of weanling gilts via the action of selected fatty acids.

The aim of this study was to examine the influence of dietary flaxseed on the endocrine and ovarian functions of weanling gilts challenged with E. coli and Coronavirus infections treated with dietary probiotic cheeses and to understand the possible mechanisms of its effects on ovarian function. Probiotics were used as a natural substitution for antibiotics and 10% dietary flaxseed is an effective prebiotic which supports the action of probiotics and has other beneficial effects on the organism. Probiotics with or without flaxseed were fed to weanling gilts starting 10 days before and lasting up until 14 days after weaning. The ovaries were measured and histologically analysed. The blood samples for the levels of steroid hormones and insulin-like growth factor I (IGF-I) were assessed using immunoassays and the levels of fatty acids were assessed using gas chromatography. All samples were collected on the day of weaning and 14 days after weaning. On the day of weaning, increased levels of linoleic acid and IGF-I was associated with higher body weight. The steroid hormones were not affected by the diet. The conversion of alpha-linolenic acid (ALA) to timodonic (EPA) and cervonic (DHA) acids were lower compared to controls, and together with high levels of myristic, palmitic and palmitoleic acids was associated with the higher proliferation and lower apoptosis in the primordial, primary and secondary follicles; although the inhibition of the cell cycle was observed in relation to the low level of eicosadienoic acid. The high levels of ALA, EPA and DHA and the low levels of myristic, palmitic and palmitoleic acids may have been the effect of flaxseed feeding 14 days post-weaning and may have had a reverse effect on the proliferation and apoptosis of ovarian follicles. These data suggest that flaxseed may suppress the follicle development in weanlings via the stimulation of apoptosis and the inhibition of proliferation via the modulation of the metabolism of selected fatty acids.

The cinnamyl alcohol dehydrogenase family in flax: Differentiation during plant growth and under stress conditions.

Cinnamyl alcohol dehydrogenase (CAD), which catalyzes the reduction of cinnamaldehydes to their alcohol derivatives, is represented by a large family of proteins. The aim of the study was to identify the CAD isoforms in flax (Linum usitatissimum L.) - LuCADs - and to determine their specificity to enhance knowledge of the mechanisms controlling cell wall lignification in flax under environmental stresses. On the basis of genome-wide analysis, we identified 15 isoforms (one in two copies) belonging to three major classes of the CAD protein family. Their specificity was determined at the transcriptomic level in different tissues/organs, under Fusarium infection and abiotic stresses. Considering the function of particular LuCADs, it was established that LuCAD1 and 2 belong to Class I and they take part in the lignification of maturing stem and in the response to cold and drought stress. The Class II members LuCAD3, LuCAD4, LuCAD5 and LuCAD6 play various roles in flax being putatively responsible for lignin synthesis in different organs or under certain conditions. The obtained results indicate that within Class II, LuCAD6 was the most abundant in seedlings and maturing stems, LuCAD3 in leaves, and LuCAD4 in stems. Comparative analysis showed that expression of LuCAD genes in roots after F. oxysporum infection had the greatest contribution to differentiation of LuCAD expression patterns. Surprisingly, most of the analyzed LuCAD isoforms had reduced expression after pathogen infection. The decrease in mRNA level was primarily observed for LuCAD6 and LuCAD4, but also LuCAD1 and 8. However, the induction of LuCAD expression was mostly characteristic for Class I LuCAD1 and 2 in leaves. For cold stress, a clear correlation with phylogenic class membership was observed. Low temperatures caused induction of CAD isoforms belonging to Class I and repression of LuCADs from Class III.

Effect of mechanical damage and wound healing on the viscoelastic properties of stems of flax cultivars (Linum usitatissimum L. cv. Eden and cv. Drakkar).

As plant fibres are increasingly used in technical textiles and their composites, underlying principles of wound healing in living plant fibres are relevant to product quality, and provide inspiration for biomimetic healing in synthetic materials. In this work, two Linum usitatissimum cultivars differing in their stem mechanical properties, cv. Eden (stems resistant to lodging) and cv. Drakkar (with more flexible stems), were grown without wound or with stems previously wounded with a cut parallel or transversal to the stem. To investigate wound healing efficiency, growth traits, stem biomechanics with Dynamic Mechanical Analysis and anatomy were analysed after 25-day recovery. Longitudinal incisions formed open wounds while transversal incisions generated stem growth restoring the whole cross-section but not the original stem organisation. In the case of transversal wound healing, all the bast fibre bundles in the perturbed area became lignified and pulled apart by parenchyma cells growth. Both Linum cultivars showed a healing efficiency from 79% to 95% with higher scores for transversal healing. Morphological and anatomical modifications of Linum were related to mechanical properties and healing ability. Alongside with an increased understanding of wound healing in plants, our results highlight their possible impact on textile quality and fibre yield.

Functional characterization of the pinoresinol-lariciresinol reductase-2 gene reveals its roles in yatein biosynthesis and flax defense response.

MAIN CONCLUSION: This study provides new insights into the biosynthesis regulation and in planta function of the lignan yatein in flax leaves. Pinoresinol-lariciresinol reductases (PLR) catalyze the conversion of pinoresinol into secoisolariciresinol (SECO) in lignan biosynthesis. Several lignans are accumulated in high concentrations, such as SECO accumulated as secoisolariciresinol diglucoside (SDG) in seeds and yatein in aerial parts, in the flax plant (Linum usitatissimum L.) from which two PLR enzymes of opposite enantioselectivity have been isolated. While LuPLR1 catalyzes the biosynthesis of (+)-SECO leading to (+)-SDG in seeds, the role(s) of the second PLR (LuPLR2) is not completely elucidated. This study provides new insights into the in planta regulation and function of the lignan yatein in flax leaves: its biosynthesis relies on a different PLR with opposite stereospecificity but also on a distinct expression regulation. RNAi technology provided evidence for the in vivo involvement of the LuPLR2 gene in the biosynthesis of (-)-yatein accumulated in flax leaves. LuPLR2 expression in different tissues and in response to stress was studied by RT-qPCR and promoter-reporter transgenesis showing that the spatio-temporal expression of the LuPLR2 gene in leaves perfectly matches the (-)-yatein accumulation and that LuPLR2 expression and yatein production are increased by methyl jasmonate and wounding. A promoter deletion approach yielded putative regulatory elements. This expression pattern in relation to a possible role for this lignan in flax defense is discussed.

Development of gravitropic response: unusual behavior of flax phloem G-fibers.

The major mechanism of gravitropism that is discussed for herbal plants is based on the nonuniform elongation of cells located on the opposite stem sides, occurring in the growing zone of an organ. However, gravitropic response of flax (Linum usitatissimum L.) is well-pronounced in the lower half of developing stem, which has ceased elongation long in advance of plant inclination. We have analyzed the stem curvature region by various approaches of microscopy and found the undescribed earlier significant modifications in primary phloem fibers that have constitutively developed G-layer. In fibers on the pulling stem side, cell portions were widened with formation of "bottlenecks" between them, leading to the "sausage-like" shape of a cell. Lumen diameter in fiber widening increased, while cell wall thickness decreased. Callose was deposited in proximity to bottlenecks and sometimes totally occluded their lumen. Structure of fiber cell wall changed considerably, with formation of breaks between G- and S-layers. Thick fibrillar structures that were revealed in fiber cell wall by light microscopy got oblique orientation instead of parallel to the fiber axis one in control plants. The described changes occurred at various combinations of gravitational and mechanical stimuli. Thus, phloem fibers with constitutively formed gelatinous cell wall, located in nonelongating parts of herbal plant, are involved in gravitropism and may become an important element in general understanding of the gravity effects on plants. We suggest flax phloem fibers as the model system to study the mechanism of plant position correction, including signal perception and transduction.

Gene expression profiling of flax (Linum usitatissimum L.) under edaphic stress.

BACKGROUND: Cultivated flax (Linum usitatissimum L.) is widely used for production of textile, food, chemical and pharmaceutical products. However, various stresses decrease flax production. Search for genes, which are involved in stress response, is necessary for breeding of adaptive cultivars. Imbalanced concentration of nutrient elements in soil decrease flax yields and also results in heritable changes in some flax lines. The appearance of Linum Insertion Sequence 1 (LIS-1) is the most studied modification. However, LIS-1 function is still unclear. RESULTS: High-throughput sequencing of transcriptome of flax plants grown under normal (N), phosphate deficient (P), and nutrient excess (NPK) conditions was carried out using Illumina platform. The assembly of transcriptome was performed, and a total of 34924, 33797, and 33698 unique transcripts for N, P, and NPK sequencing libraries were identified, respectively. We have not revealed any LIS-1 derived mRNA in our sequencing data. The analysis of high-throughput sequencing data allowed us to identify genes with potentially differential expression under imbalanced nutrition. For further investigation with qPCR, 15 genes were chosen and their expression levels were evaluated in the extended sampling of 31 flax plants. Significant expression alterations were revealed for genes encoding WRKY and JAZ protein families under P and NPK conditions. Moreover, the alterations of WRKY family genes differed depending on LIS-1 presence in flax plant genome. Besides, we revealed slight and LIS-1 independent mRNA level changes of KRP2 and ING1 genes, which are adjacent to LIS-1, under nutrition stress. CONCLUSIONS: Differentially expressed genes were identified in flax plants, which were grown under phosphate deficiency and excess nutrition, on the basis of high-throughput sequencing and qPCR data. We showed that WRKY and JAS gene families participate in flax response to imbalanced nutrient content in soil. Besides, we have not identified any mRNA, which could be derived from LIS-1, in our transcriptome sequencing data. Expression of LIS-1 flanking genes, ING1 and KRP2, was suggested not to be nutrient stress-induced. Obtained results provide new insights into edaphic stress response in flax and the role of LIS-1 in these process.

Differential effects of cadmium and chromium on growth, photosynthetic activity, and metal uptake of Linum usitatissimum in association with Glomus intraradices.

The current study was aimed at analyzing the differential effects of heavy metals (cadmium and chromium) and mycorrhizal fungus; Glomus intraradices on growth, chlorophyll content, proline production, and metal accumulation in flax plant (Linum usitatissimum L.). Heavy metal accumulation rate in flax varied from 90 to 95 % for Cd and 61-84 % for Cr at a concentration range of 250 to 500 ppm for both metals in 24 days of experiment. Growth and photosynthetic activity of flax reduced to an average of 21 and 45 %, respectively. However, inoculation of G. intraradices significantly increased the plant biomass even under metal stressed conditions. Additionally, mycorrhizal association also assists the Cd and Cr increased uptake by 23 and 33 %, respectively. Due to metal stress, chlorophyll contents were decreased by 27 and 45 %, while 84 and 71 % increased proline content was observed under Cd and Cr stress, respectively. The present results clearly signify the differential response and potential of flax plant towards heavy metal tolerance and accumulation that can further increase with mycorrhizal fungus.

Does biopolymers composition in seeds contribute to the flax resistance against the Fusarium infection?

Over the last decades, the cultivation of fibrous flax declined heavily. There are number of reasons for that fact; one of them is flax susceptibility to the pathogen infection. Damages caused mainly by fungi from genus Fusarium lead to the significant losses when cultivating flax, which in turn discourage farmers to grow flax. Therefore, to launch the new products from flax with attractive properties there is a need to obtain new flax varieties with increased resistance to pathogens. In order to obtain the better quality of flax fiber, we previously generated flax with reduced pectin or lignin level (cell wall polymers). The modifications altered also plants' resistance to the Fusarium infection. Undoubtedly, the plant defense system is complex, however, in this article we aimed to investigate the composition of modified flax seeds and to correlate it with the observed changes in the flax resistance to the pathogen attack. In particular, we evaluated the content and composition of carbohydrates (cell wall polymers: pectin, cellulose, hemicelluloses and mucilage), and phenylpropanoid compounds (lignin, lignans, phenolics). From the obtained results we concluded that the observed changes in the vulnerability to pathogens putatively correlate with the antioxidant potential of phenylpropanoids accumulated in seeds, seco-isolariciresinol and coumaric acid diglycosides in particular, and with pectin level as a carbon source for pathogens. Surprisingly, relatively less important for the resistance was the physical barrier, including lignin and cellulose amount and cellulose structure. Certainly, the hypothesis should be verified on a larger number of genotypes.

Identification of differentially expressed genes in flax (Linum usitatissimum L.) under saline-alkaline stress by digital gene expression.

The salinization and alkalization of soil are widespread environmental problems, and alkaline salt stress is more destructive than neutral salt stress. Therefore, understanding the mechanism of plant tolerance to saline-alkaline stress has become a major challenge. However, little attention has been paid to the mechanism of plant alkaline salt tolerance. In this study, gene expression profiling of flax was analyzed under alkaline-salt stress (AS2), neutral salt stress (NSS) and alkaline stress (AS) by digital gene expression. Three-week-old flax seedlings were placed in 25 mM Na2CO3 (pH11.6) (AS2), 50mM NaCl (NSS) and NaOH (pH11.6) (AS) for 18 h. There were 7736, 1566 and 454 differentially expressed genes in AS2, NSS and AS compared to CK, respectively. The GO category gene enrichment analysis revealed that photosynthesis was particularly affected in AS2, carbohydrate metabolism was particularly affected in NSS, and the response to biotic stimulus was particularly affected in AS. We also analyzed the expression pattern of five categories of genes including transcription factors, signaling transduction proteins, phytohormones, reactive oxygen species proteins and transporters under these three stresses. Some key regulatory gene families involved in abiotic stress, such as WRKY, MAPKKK, ABA, PrxR and ion channels, were differentially expressed. Compared with NSS and AS, AS2 triggered more differentially expressed genes and special pathways, indicating that the mechanism of AS2 was more complex than NSS and AS. To the best of our knowledge, this was the first transcriptome analysis of flax in response to saline-alkaline stress. These data indicate that common and diverse features of saline-alkaline stress provide novel insights into the molecular mechanisms of plant saline-alkaline tolerance and offer a number of candidate genes as potential markers of tolerance to saline-alkaline stress.

Variability of seed traits and properties of soluble mucilages in lines of the flax genetic collection of Vavilov Institute.

Upon hydration, flax seeds secrete mucilages whose content and physico-chemical properties vary according to the genotype and environment. The aim of the work was to investigate the complex genetic relationships between the vegetative period, colour, size and production of seed, the composition (polysaccharides and proteins) and physico-chemical properties of soluble mucilages collected at 28 °C from seeds of 18 lines grown in St Petersburg area. The vegetative period duration was found to impact the size and production of seeds, the yield of mucilages, including the polysaccharides, and the galactosidase enzymes, as well as their composition (mainly the rhamnogalacturonan I moieties) and some of their properties (mainly viscosity). Data allowed to significantly distinguish 6 fibre lines with mucilages enriched in rhamnogalacturonan I, 6 lines with mucilages enriched in arabinoxylan including 5 linseeds and 1 mutated fibre-line, and 5 lines with mucilages enriched in homogalacturonan-like polymer including 4 fibre lines and 1 brown linseed. Seven fibre lines had mucilages particularly rich in galactose. High to very high variability was found for 14 traits. Relatively independent characters (form/shape, protein and galactosidase) were identified and could be combined by breeding, with a focus on mucilage yield, composition and properties. Main-component analyses of line characters showed a large diversity in linseeds mainly due to their different origin but small variation in Russian fibre lines with brown seeds.

Osmotic stress alters the balance between organic and inorganic solutes in flax (Linum usitatissimum).

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.

The LuWD40-1 gene encoding WD repeat protein regulates growth and pollen viability in flax (Linum Usitatissimum L.).

As a crop, flax holds significant commercial value for its omega-3 rich oilseeds and stem fibres. Canada is the largest producer of linseed but there exists scope for significant yield improvements. Implementation of mechanisms such as male sterility can permit the development of hybrids to assist in achieving this goal. Temperature sensitive male sterility has been reported in flax but the leakiness of this system in field conditions limits the production of quality hybrid seeds. Here, we characterized a 2,588 bp transcript differentially expressed in male sterile lines of flax. The twelve intron gene predicted to encode a 368 amino acid protein has five WD40 repeats which, in silico, form a propeller structure with putative nucleic acid and histone binding capabilities. The LuWD40-1 protein localized to the nucleus and its expression increased during the transition and continued through the vegetative stages (seed, etiolated seedling, stem) while the transcript levels declined during reproductive development (ovary, anthers) and embryonic morphogenesis of male fertile plants. Knockout lines for LuWD40-1 in flax failed to develop shoots while overexpression lines showed delayed growth phenotype and were male sterile. The non-viable flowers failed to open and the pollen grains from these flowers were empty. Three independent transgenic lines overexpressing the LuWD40-1 gene had ∼80% non-viable pollen, reduced branching, delayed flowering and maturity compared to male fertile genotypes. The present study provides new insights into a male sterility mechanism present in flax.

Comparative demography of two co-occurring Linum species with different distribution patterns.

Understanding similarities and differences in population dynamics of closely related species is a key prerequisite in attempts to apply knowledge obtained in one species to another species, e.g., for the purpose of predicting future fate of populations of various rare species. It can be expected that species will have similar population dynamics if they are closely related and share similar habitats. Contrasting population sizes and distribution patterns may, however, indicate that the population dynamics will be different. To understand similarities and differences in population dynamics of closely related species, I studied demography of two congeneric endangered species, Linum flavum and L. tenuifolium co-occurring in dry grasslands. Linum flavum occurs with a lower number of large populations, while L. tenuifolium occurs as a large number of small populations. The results showed that L. flavum had higher population growth rates, relied more on survival and growth and its populations were more persistent. In contrast, populations of L. tenuifolium were more prone to extinction and frequent recolonisation was necessary for their survival in the landscape. This was in accordance with observed population sizes of the two species and their frequency in the landscape. The results indicate that despite being closely related and occurring in the same habitat types, the two Linum species have different growth strategies. The strong differences in population dynamics between the two species suggest that similarity in population sizes and frequency of the species in the landscape may be more important when attempting to transfer knowledge between species than is taxonomic relatedness.

Efficiency of yeast in enhancement of the oxidative defense system in salt-stressed flax seedlings.

The combined effects of yeast (1 ppm) and salinity on germination, seedling growth, metabolite accumulation and antioxidant defense system of flax (Linum usitatissimum) seeds grown at 100, 200 and 300 mM NaCl were studied. In this investigation, the germination was completely inhibited at 300 mM NaCl. Moreover, salinity induced marked increases in lipid peroxidation product (MDA), soluble carbohydrates as well as the reduced glutathione which were concomitant with sharp decrease in total phenols and ascorbic acid contents in 12-day-old flax seedlings. Furthermore, NaCl treatments increased the activities of some antioxidant enzymes (superoxide dismutase; SOD, peroxidase; POX and polyphenol oxidase; PPO). On the other hand, yeast treatments under salinity stress restored the membrane integrity and improved seedling growth. The results suggested that yeast treatments mitigated salinity stress via accumulation of some osmoprotectants such as free amino acids particularly proline which associated with elevating the defense system in terms of ascorbic acid, glutathione and total phenol contents. Yeast treatments also stimulated the activities of some antioxidant enzymes, preventing membrane peroxidation resulting in high capacity for germination and improved seedling growth under sever salt stress.