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Etude biochimique et immunocytochimique de l'impact de mutations génétiques sur la lignification et l'assemblage des parois d'Arabidopsis thaliana

Abstract : In recent years plant biomass has become the subject of a large interest for the industrial uses of wood and agricultural residues and for its potential use for new energy sources. For all these utilisations the lignocellulosic cell wall plays a central role. The work of this thesis was undertaken to gain an improved knowledge of the detailed structure and organisation of the lignified secondary wall and of the function of the polymer constituents in the edification of the plant cell wall biocomposite.
Several knock-out mutants of the model plant Arabidopsis thaliana deficient for one or more genes involved in lignin monomers biosynthesis (cinnamoyl-CoA-reductase, ccr1; cinnamyl alcohol dehydrogenase, cad-c and cad-d; aldehyde dehydrogenase, ref1 ; ferulate 5-hydroxylase, f5h) were investigated for the analysis of the consequences of the mutation on the composition and the structure of the cell walls. Biochemical analysis of the mutant lines by thioacidolysis, and immuno-topochemistry in electron microscopy, respectively, constituted the two main approaches implemented to characterise the impacts of the mutations on the structure of lignins and on the macromolecular assembly of the cell walls. Our results revealed that the consequences of the mutations were tissue-specific, suggesting that lignification is spatio-temporally regulated during differentiation. The analysis of the alterations induced by the different mutations in the assembly of the cell walls suggested that the non-condensed structures of lignin had an important role in the cohesion of the cell wall composite. The comparison of the impacts of the different genes and gene combinations showed that the effects on the lignins and on the walls are not the simple summation of the effect of each individual gene. The development of a new approach of microanalysis involving the technique of laser capture microdissection allowed to precise for the first time the analytical differences of the lignins from fibres and vessels, and showed a great potential for the characterisation of the effects of mutations at the tissue scale.
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Contributor : Jimmy Berrio-Sierra <>
Submitted on : Tuesday, January 29, 2008 - 8:26:14 PM
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Jimmy Berrio-Sierra. Etude biochimique et immunocytochimique de l'impact de mutations génétiques sur la lignification et l'assemblage des parois d'Arabidopsis thaliana. Biologie végétale. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00223893⟩

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