{"id":117336,"date":"2018-03-11T10:46:47","date_gmt":"2018-03-11T10:46:47","guid":{"rendered":"https:\/\/www.deberes.net\/tesis\/sin-categoria\/caracterizacion-funcional-de-mutantes-de-peroxidasas-implicadas-en-la-biosa%c2%adntesis-de-ligninas-en-arabidopsis-thaliana\/"},"modified":"2018-03-11T10:46:47","modified_gmt":"2018-03-11T10:46:47","slug":"caracterizacion-funcional-de-mutantes-de-peroxidasas-implicadas-en-la-biosa%c2%adntesis-de-ligninas-en-arabidopsis-thaliana","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/fisiologia-vegetal\/caracterizacion-funcional-de-mutantes-de-peroxidasas-implicadas-en-la-biosa%c2%adntesis-de-ligninas-en-arabidopsis-thaliana\/","title":{"rendered":"Caracterizaci\u00f3n funcional de mutantes de peroxidasas implicadas en la bios\u00edntesis de ligninas en arabidopsis thaliana"},"content":{"rendered":"<h2>Tesis doctoral de <strong> Francisco Fern\u00e1ndez P\u00e9rez <\/strong><\/h2>\n<p>Resumen la lignificaci\u00f3n de la pared de las c\u00e9lulas del xilema es un proceso extremadamente complejo, sometido a un estrecho control hormonal cuya funci\u00f3n principal es la de conferir rigidez e impermeabilidad al sistema vascular. La lignificaci\u00f3n es una secuencia de reacciones en cadena que conducen desde un metabolito primario, la fenilalanina, hasta los precursores inmediatos de las ligninas, los alcoholes hidroxicinam\u00edlicos (p-cumar\u00edlico, conifer\u00edlico y sinap\u00edlico). Estos alcoholes son oxidados, finalmente, por las peroxidasas para dar lugar a sus correspondientes radicales, que se ensamblan en la pared celular generando un pol\u00edmero hidrof\u00f3bico y fuertemente polidisperso, que da rigidez e impermeabiliza la pared celular, constituyendo uno de los mayores sumideros metab\u00f3licos del co2 fijado durante la fotos\u00edntesis. las peroxidasas siringilo son las enzimas responsables de la oxidaci\u00f3n del alcohol sinap\u00edlico, lo que conduce a la formaci\u00f3n de mon\u00f3meros siringilo (s) que se incorporan al pol\u00edmero de lignina. Estas enzimas han sido descritas como peroxidasas b\u00e1sicas que no presentan restricciones est\u00e9ricas que impidan la entrada de alcohol sinap\u00edlico en el centro catal\u00edtico. Hasta el momento, las peroxidasas m\u00e1s estudiadas a nivel estructural han sido la atp a2 de arabidopsis y hrp a2 de r\u00e1bano, las cuales son peroxidasas guaiacilo incapaces de oxidar el alcohol sinap\u00edlico. La peroxidasa siringilo mejor caracterizada hasta el momento es la de zinnia elegans (zeprx). En el genoma de arabidopsis existen 73 peroxidasas pero ninguna de ellas ha sido identificada como una peroxidasa de tipo siringilo. Estudios previos buscaron en el genoma de a. Thaliana peroxidasas que presentan una gran homolog\u00eda de secuencia con zeprx, as\u00ed como de estructura, carga superficial, punto isoel\u00e9ctrico y regulaci\u00f3n de su expresi\u00f3n. Teniendo en cuenta estos criterios se seleccionaron las peroxidasas atprx4, atprx52, y atprx72.  en esta tesis, se muestra c\u00f3mo la supresi\u00f3n de dichas peroxidasas en diferentes l\u00edneas mutantes de arabidopsis afecta al contenido y a la composici\u00f3n de ligninas. En general, todas las l\u00edneas mutantes mostraron una disminuci\u00f3n en el contenido de ligninas, medido con bromuro de acetilo, entre un 17 y un 37%. Adem\u00e1s, la relaci\u00f3n s\/g, obtenida por tioacidolisis, indica una disminuci\u00f3n en las unidades de s en todos los mutantes. Adem\u00e1s, como se deduce de las tinciones de wiesner y de m\u00ed\u00a4ule, esta reducci\u00f3n en el contenido de mon\u00f3meros s parece estar restringida a las fibras interfasciculares, pero no afecta a los vasos del xilema. Para analizar si este cambio en la composici\u00f3n de lignina era dependiente de la edad de la planta, tambi\u00e9n se realizaron an\u00e1lisis cualitativos y cuantitativos de ligninas en tallos en diferentes etapas de desarrollo. Nuestros resultados mostraron diferencias significativas en el contenido y la composici\u00f3n de ligninas entre plantas mutantes y wt solamente en las \u00faltimas etapas del desarrollo. Sin embargo, no se encontraron diferencias significativas en el tama\u00f1o de las plantas mutantes en comparaci\u00f3n con el wt. Los an\u00e1lisis mediante qpcr revelaron que los genes implicados en la bios\u00edntesis de ligninas, as\u00ed como en la formaci\u00f3n de la pared celular secundaria, redujeron su expresi\u00f3n en las plantas mutantes. Por otro lado, la expresi\u00f3n de genes implicados en la bios\u00edntesis de \u00e9steres sinapato y de flavonoides se increment\u00f3 en las plantas mutantes con respecto al wt lo cual indica que hay una reorientaci\u00f3n de los esqueletos carbonados de la ruta de bios\u00edntesis de las ligninas hacia otras rutas del metabolismo fenilpropanoide. En conjunto, nuestros resultados sugieren que atprx4, atprx52 y atprx72 son peroxidasas siringilo implicados en la s\u00edntesis de unidades s en las fibras interfasciculares y adem\u00e1s, su represi\u00f3n afecta a toda la ruta fenilpropanoide y puede ser suficiente para alterar el metabolismo de la planta.  abstract the lignification of xylem cell walls is an extremely complex process, under strict hormonal control, whose main function is to confer rigidity and impermeability to the vascular system. Lignification is the result of several reactions from a primary metabolite, phenylalanine, until the immediate precursors of lignin, the hydroxycinnamyl (p-coumaryl, coniferyl and sinapyl) alcohols. These alcohols are finally oxidized by peroxidases to give their corresponding radicals, which will be further assembled in the cell wall,  generating a hydrophobic polymer (lignin) which gives rigidity and waterproof cell wall. Lignin constitutes a major metabolic sink for the co2 fixed during photosynthesis. syringyl peroxidases are the enzymes responsible for sinapyl alcohol oxidation that eventually lead to syringyl monomers formation. They have been described as basic peroxidases which show no steric restrictions that hinder the entry of sinapyl alcohol into the catalytic centre. So far, the most studied peroxidases at the structural level, such as atp a2 from arabidopsis and hrp a2 from horseradish, are guaiacyl peroxidases, unable to oxidize sinapyl alcohol. Unfortunately, little is known regarding structure and catalytic properties of syringyl peroxidases. The best characterized is zeprx from zinnia elegans. Since such a peroxidase similar to zeprx has not been identified in arabidopsis, a search through a. Thaliana genome was performed, in order to identify the peroxidases which showed the highest homology to zeprx. Based on several structural and molecular characteristics, atprx4, atprx52 and atprx72 were determined to be the most likely homologous to zeprx in arabidopsis.  in this thesis, we show how the suppression of atprx4, atprx52 and atprx72 in different mutant lines of arabidopsis affects lignin content and composition. Overall, all the mutant lines showed a decreased in lignin content, measured with acetyl bromide, ranging from 17 to 37%. Furthermore, the s\/g ratio, obtained by both nitrobenzene oxidation and thioacidolysis, indicated a decrease in s units in all the mutants. As deduced from wiesner and mainly m\u00ed\u00a4ule stainings, this reduction in s monomers content seems to be restricted to the interfascicular fibers, but it does not affect xylem vessels. To assay whether this shift in lignin composition was age-dependent, we also performed qualitative and quantitative analyses of lignins in stems at different stages of development. Our results showed significant differences in both content and composition only in late stages of development of mutant plants. However, no significant differences were found regarding mutant size in comparison with wt when plants reached maturity. Qpcr revealed that genes involved in lignin biosynthesis as well as in secondary cell wall formation were down-regulated in mutant plants. On the other hand, expression of genes involved in sinapate esters and flavonoid biosynthesis was up-regulated in mutant plants, which indicates a reallocation of carbon from lignin biosynthetic pathway to other routes of phenylpropanoid metabolism. Taken together, our results indicate that atprx4, atprx52 and atprx72 may be syringyl peroxidases involved in the synthesis of s units in interfascicular fibers. Moreover, the suppression of the last step of syringyl lignins biosynthesis affects the whole phenylpropanoid pathway and may be sufficient to alter plant metabolism.<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Caracterizaci\u00f3n funcional de mutantes de peroxidasas implicadas en la bios\u00edntesis de ligninas en arabidopsis thaliana<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Caracterizaci\u00f3n funcional de mutantes de peroxidasas implicadas en la bios\u00edntesis de ligninas en arabidopsis thaliana <\/li>\n<li><strong>Autor:<\/strong>\u00a0 Francisco Fern\u00e1ndez P\u00e9rez <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Murcia<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 27\/03\/2015<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3>Direcci\u00f3n y tribunal<\/h3>\n<ul>\n<li><strong>Director de la tesis<\/strong>\n<ul>\n<li>Mar\u00eda  Angeles Pedre\u00f1o Garcia<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: manuel Acosta echeverria <\/li>\n<li>Mar\u00eda  angeles Ferrer ayala (vocal)<\/li>\n<li>federico Pomar barbeito (vocal)<\/li>\n<li>Jos\u00e9 Antonio Hernandez cortes (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Francisco Fern\u00e1ndez P\u00e9rez Resumen la lignificaci\u00f3n de la pared de las c\u00e9lulas del xilema es un proceso [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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