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• W35252170 abstract "Aproximacio als mecanismes moleculars implicats en la regulacio de la sindrome de fugida de l?ombra en Arabidopsis. La llum es un element essencial per les plantes, ja que d?ella en treuen l?energia necessaria per creixer. Es normal doncs que hagin adquirit mecanismes per percebre diferents parametres d?aquesta, relacionats tant amb la seva quantitat com amb la qualitat. Dels diferents receptors de llum o fotoreceptors, els fitocroms son els mes estudiats. Probablement la resposta controlada pels fitocroms mes important per a les plantes a la naturalesa es la sindrome de fugida de l?ombra (SAS, de l?angles shade avoidance syndrome). Aquesta sindrome agrupa una serie de respostes que han adoptat les plantes amb flors per evitar l?ombra de la vegetacio propera. Tals respostes, com l?allargament de l?hipocotil, la disminucio de l'expansio foliar o la floracio primerenca, impliquen a la fi una disminucio de la biomassa en general. L?estudi de la SAS, per tant, es perfila com de gran interes biotecnologic, i ha estat objecte de la manipulacio genetica per tal de millorar el rendiment dels cultius. En la present tesi s?ha treballat amb dos factors previament identificats al laboratori i involucrats en les respostes de la SAS. 1. Estudi de la relacio estructura-funcio del factor regulador de la SAS ATHB4. D?una banda s?ha estudiat el factor de transcripcio ATHB4, una proteina de la familia HD-Zip (de l?angles homeodomain-leucine zipper) classe II. La sobre-expressio d?ATHB4 produeix plantules mes petites i fosques, amb hipocotil lleugerament allargat i cotiledons estrets, i respostes molt menors a tractaments d?ombra. Mitjancant la sobre-expressio de diferents regions d?ATHB4 s?ha vist que proteines sense la regio Ct mantenen la mateixa activitat biologica que la sobre-expressio de la proteina sencera, suggerint que la regio Ct no te rellevancia en les respostes a ombra aplicada al laboratori. D?altra banda, linies sobre-expressant diverses parts d?ATHB4 sense la regio Nt, o amb mutacions en residus conservats d?aquesta, perden gran part del fenotip visible en la linia sobre-expressora d?ATHB4 sencera, suggerint que aquesta regio Nt es essencial per l?activitat d?ATHB4 en les respostes a ombra. A mes, formes truncades d?ATHB4 que podrien tenir la capacitat d?unio al DNA afectada mantenen les mateixes respostes a ombra que la proteina sencera, suggerint que ATHB4 podria actuar en ombra de manera independent a la unio al DNA. Conjuntament, els resultats fisiologics i moleculars de les diferents construccions analitzades en la present tesi, suggereixen que la regio Nt d?ATHB4 podria interaccionar amb altres proteines per tal de regular les respostes de la SAS. 2. Paper de les nucleoporines (NUPs) en la regulacio de la SAS. En un escrutini genetic es va obtenir el mutant recessiu dracula2 (dra2) amb una resposta a ombra simulada atenuada. Aquesta mutacio afecta un gen que codifica una possible NUP. L?al?lel obtingut de l?escrutini es va anomenar dra2-1. En la present tesi s?ha realitzat una caracteritzacio general d?aquest mutant, i d?altres al?lels mutants del mateix gen per insercio de T-DNA, mitjancant quantificacions dels nivells de pigments (clorofil?les i carotenoides), respostes a hormones (BRs, GAs i auxines) i respostes a ombra, tant fisiologiques com moleculars. S?ha vist que aquest mutant presenta alteracions en diverses respostes, inclosa l?exportacio d?mRNAs del nucli cap al citoplasma. A mes, altres NUPs tambe afecten les respostes de la SAS a nivell fisiologic, pero dra2-1 es l?unic amb efectes moleculars. En conjunt, en la present tesi presentem les NUPs com a elements importants per les correctes respostes de la SAS, tenint DRA2 algun paper especific en la senyalitzacio per llum. c) Extracte en angles (348 paraules/350). Tesi doctoral de Marcal Gallemi Rovira, programa de biotecnologia. Study of the molecular mechanisms involved in the shade avoidance syndrome in Arabidopsis. Plants sense the presence of competing neighboring vegetation as a change in light quality: i.e. they sense the reduced ratio of red to far-red light. The responses to shade, generally referred to as the shade avoidance syndrome (SAS), involve various developmental changes intended to outgrow or outcompete the neighboring plants. A shade-responsive luciferase reporter line (PHYB::LUC) was used to carry out a high-throughput screen to identify novel SAS mutants. The dracula 2 (dra2) mutant, that showed a reduced avoidance of shade, affected a gene encoding a nucleoporine-like protein. Nucleoporins (NUPs) are the components of the nuclear pore complex (NPC), a structure that regulates the nucleocytoplasmic transport. Our work demonstrate that a proper nucleocytoplasmic transport is needed for SAS responses, as several plant NUP mutants display attenuated physiological shade responses. Despite the pleiotropic phenotype of the loss of function of specific NUPs, we found that dra2-1 has some specific and distinct molecular activity by reducing the expression of several shade molecular markers. In summary, we propose that DRA2 is a true NUP with a unique role regulating nucleocytoplasmic traffic of SAS related macromolecules. ATHB4, a transcription factor of the homeodomain-leucine-zipper class II (HD-Zip II) family, participates in integrating shade perception and hormone-mediated growth and, on the other hand, regulating leaf and cotyledon development. In this work we demonstrated that ATHB4 is a transcription factor that binds DNA and repress the expression of some members of its own family. By means of a structure-function approach, we go further in the study of the biological activity of ATHB4 in the shade-modulated hypocotyl elongation and control of gene expression in transgenic plants. We found that the HD and Zip domains, which hold the DNA-binding as a dimer, is not required for the role of ATHB4 in SAS responses. By contrast, the N-terminal region, which is conserved between most of the HD-Zip II members and contains a putative EAR domain, is essential for the proper SAS activity. Taking together our results indicate that ATHB4 plays two different roles, one in plant development and other in SAS responses, and that for the shade related activity is not working as a DNA-binding transcriptional repressor." @default.
• W35252170 created "2016-06-24" @default.
• W35252170 creator A5032906236 @default.
• W35252170 date "2013-12-03" @default.
• W35252170 modified "2023-09-26" @default.
• W35252170 title "Aproximació als mecanismes moleculars implicats en la regulació de la síndrome de fugida de l’ombra en Arabidopsis" @default.
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