Lignin genes regulation in Flax bast fibers

Le lin est une plante annuelle cultivée pour ses fibres longues et ses graines oléagineuses. Les fibres sont traditionnellement employées dans l’industrie textile et, depuis peu, incorporées dans des agro-matériaux. Les fibres longues sont situées dans la tige entre l’écorce et le bois, en périphérie du phloème. Les cellules fibreuses sont essentiellement composées de parois secondaires dans lesquelles la teneur en lignine est faible (2% à 4%). C’est pourquoi, elles sont qualifiées d’« hypolignifiées ». En effet, une paroi secondaire « classique » est généralement composée de 40 à 50% de cellulose et de 20 à 30% de lignine. Ainsi, nous suggérons l'existence d'une régulation particulière lors de la mise en place de cette paroi. On ne retrouve ce type de paroi secondaire que dans de très rares cas chez les végétaux comme dans d'autres fibres phloémiennes présentes par exemple chez le chanvre, mais aussi dans les couches G du bois de tension. Le lin est donc un bon modèle d’étude pour la compréhension de la régulation de la lignification des parois secondaires. Mes travaux visent ainsi à améliorer nos connaissances sur les mécanismes cellulaires et moléculaires permettant de mettre en place une telle paroi. Les raisons pour lesquelles ces fibres contiennent de faibles quantités de lignine demeurent complètement inconnues. Différentes pistes peuvent être explorées et parmi celles-ci, l'existence de phénomènes de régulations géniques spécifiques à ces types cellulaires. Les travaux réalisés dans le cadre de ma thèse s'inscrivent dans l'hypothèse de l'existence d'une régulation transcriptionnelle à ce niveau.Flax is an annual species cultivated for its fibers and seed oil. Flax bast fibers are traditionally used in textiles and since more recently, they are integrated in composite materials used in automobile and construction industries. These fibers are located between the epidermis and the secondary xylem. Their cell walls contain unusually low amounts of lignin (2 %) compared to more classical secondary cell walls (between 20 and 30 %). So we suggest the existence of a special regulatory control of lignification within these fibers. The same types of cell walls also exist in other bast fibers such as in hemp but also in the G-layer of tension wood. Flax is a suitable model to gain knowledge on the lignification process. The reason why the bast fibers are hypolignified is completely unknown and may be due to a regulatory control at the gene transcription level

Régulation des gènes lignine chez le lin à fibres, Linum usitatissimum L.

Le lin est une plante annuelle cultivée pour ses fibres longues et ses graines oléagineuses. Les fibres sont traditionnellement employées dans l industrie textile et, depuis peu, incorporées dans des agro-matériaux. Les fibres longues sont situées dans la tige entre l écorce et le bois, en périphérie du phloème. Les cellules fibreuses sont essentiellement composées de parois secondaires dans lesquelles la teneur en lignine est faible (2% à 4%). C est pourquoi, elles sont qualifiées d hypolignifiées . En effet, une paroi secondaire classique est généralement composée de 40 à 50% de cellulose et de 20 à 30% de lignine. Ainsi, nous suggérons l'existence d'une régulation particulière lors de la mise en place de cette paroi. On ne retrouve ce type de paroi secondaire que dans de très rares cas chez les végétaux comme dans d'autres fibres phloémiennes présentes par exemple chez le chanvre, mais aussi dans les couches G du bois de tension. Le lin est donc un bon modèle d étude pour la compréhension de la régulation de la lignification des parois secondaires. Mes travaux visent ainsi à améliorer nos connaissances sur les mécanismes cellulaires et moléculaires permettant de mettre en place une telle paroi. Les raisons pour lesquelles ces fibres contiennent de faibles quantités de lignine demeurent complètement inconnues. Différentes pistes peuvent être explorées et parmi celles-ci, l'existence de phénomènes de régulations géniques spécifiques à ces types cellulaires. Les travaux réalisés dans le cadre de ma thèse s'inscrivent dans l'hypothèse de l'existence d'une régulation transcriptionnelle à ce niveau.Flax is an annual species cultivated for its fibers and seed oil. Flax bast fibers are traditionally used in textiles and since more recently, they are integrated in composite materials used in automobile and construction industries. These fibers are located between the epidermis and the secondary xylem. Their cell walls contain unusually low amounts of lignin (2 %) compared to more classical secondary cell walls (between 20 and 30 %). So we suggest the existence of a special regulatory control of lignification within these fibers. The same types of cell walls also exist in other bast fibers such as in hemp but also in the G-layer of tension wood. Flax is a suitable model to gain knowledge on the lignification process. The reason why the bast fibers are hypolignified is completely unknown and may be due to a regulatory control at the gene transcription level.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Selection of reference genes for quantitative gene expression normalization in flax (<it>Linum usitatissimum </it>L.)

<p>Abstract</p> <p>Background</p> <p>Quantitative real-time PCR (qRT-PCR) is currently the most accurate method for detecting differential gene expression. Such an approach depends on the identification of uniformly expressed 'housekeeping genes' (HKGs). Extensive transcriptomic data mining and experimental validation in different model plants have shown that the reliability of these endogenous controls can be influenced by the plant species, growth conditions and organs/tissues examined. It is therefore important to identify the best reference genes to use in each biological system before using qRT-PCR to investigate differential gene expression. In this paper we evaluate different candidate HKGs for developmental transcriptomic studies in the economically-important flax fiber- and oil-crop (<it>Linum usitatissimum </it>L).</p> <p>Results</p> <p>Specific primers were designed in order to quantify the expression levels of 20 different potential housekeeping genes in flax roots, internal- and external-stem tissues, leaves and flowers at different developmental stages. After calculations of PCR efficiencies, 13 HKGs were retained and their expression stabilities evaluated by the computer algorithms geNorm and NormFinder. According to geNorm, 2 Transcriptional Elongation Factors (TEFs) and 1 Ubiquitin gene are necessary for normalizing gene expression when all studied samples are considered. However, only 2 TEFs are required for normalizing expression in stem tissues. In contrast, NormFinder identified glyceraldehyde-3-phosphate dehydrogenase (GADPH) as the most stably expressed gene when all samples were grouped together, as well as when samples were classed into different sub-groups.</p> <p>qRT-PCR was then used to investigate the relative expression levels of two splice variants of the flax <it>LuMYB1 </it>gene (homologue of <it>AtMYB59</it>). <it>LuMYB1-1 </it>and <it>LuMYB1-2 </it>were highly expressed in the internal stem tissues as compared to outer stem tissues and other samples. This result was confirmed with both geNorm-designated- and NormFinder-designated-reference genes.</p> <p>Conclusions</p> <p>The use of 2 different statistical algorithms results in the identification of different combinations of flax HKGs for expression data normalization. Despite such differences, the use of geNorm-designated- and NormFinder-designated-reference genes enabled us to accurately compare the expression levels of a flax MYB gene in different organs and tissues. Our identification and validation of suitable flax HKGs will facilitate future developmental transcriptomic studies in this economically-important plant.</p

Natural hypolignification is associated with extensive oligolignol accumulation in flax stems

Flax (Linum usitatissimum) stems contain cells showing contrasting cell wall structure: lignified in inner stem xylem tissue and hypolignified in outer stem bast fibers. We hypothesized that stem hypolignification should be associated with extensive phenolic accumulation and used metabolomics and transcriptomics to characterize these two tissues. H-1 nuclear magnetic resonance clearly distinguished inner and outer stem tissues and identified different primary and secondary metabolites, including coniferin and p-coumaryl alcohol glucoside. Ultrahigh-performance liquid chromatography-Fourier transform ion cyclotron resonance-mass spectrometry aromatic profiling (lignomics) identified 81 phenolic compounds, of which 65 were identified, to our knowledge, for the first time in flax and 11 for the first time in higher plants. Both aglycone forms and glycosides of monolignols, lignin oligomers, and (neo)lignans were identified in both inner and outer stem tissues, with a preponderance of glycosides in the hypolignified outer stem, indicating the existence of a complex monolignol metabolism. The presence of coniferin-containing secondary metabolites suggested that coniferyl alcohol, in addition to being used in lignin and (neo)lignan formation, was also utilized in a third, partially uncharacterized metabolic pathway. Hypolignification of bast fibers in outer stem tissues was correlated with the low transcript abundance of monolignol biosynthetic genes, laccase genes, and certain peroxidase genes, suggesting that flax hypolignification is transcriptionally regulated. Transcripts of the key lignan genes Pinoresinol-Lariciresinol Reductase and Phenylcoumaran Benzylic Ether Reductase were also highly abundant in flax inner stem tissues. Expression profiling allowed the identification of NAC (NAM, ATAF1/2, CUC2) and MYB transcription factors that are likely involved in regulating both monolignol production and polymerization as well as (neo) lignan production

Nutritional composition and rearing potential of the meadow grasshopper ( Chorthippus parallelus Zetterstedt)

peer reviewedInsects, particularly those belonging to the family Acrididae (grasshoppers), are commonly consumed as human food in many parts of the world. Grasshoppers of the species Chorthippus parallelus are abundantly found throughout Europe. However, these insects were not consumed by Europeans till now, but could possibly be used as human food, which is why we investigated their chemical composition. We found that they contain high level of proteins (69%), with an excellent amino acid profile and protein digestibility (97%). Furthermore, specimens of C. parallelus have an interesting fatty acids profile and minerals composition. Preliminary toxicity assessment indicates that these insects do not exhibit toxicity towards neutrophil cells (white blood cells). These data suggest that C. parallelus could be considered for human consumption. Rearing trials done during the study show that commercial rearing could be developed to produce sufficient biomass for sustaining human consumption