Search

When plants grow in close proximity basic resources such as light can become limiting. Under such conditions plants respond to anticipate and/or adapt to the light shortage, a process known as the shade avoidance syndrome (SAS). Following genetic screening using a shade-responsive luciferase reporter line (PHYB:LUC), we identified DRACULA2 (DRA2), which encodes an Arabidopsis homolog of mammalian nucleoporin 98, a component of the nuclear pore complex (NPC). DRA2, together with other nucleoporins, participates positively in the control of the hypocotyl elongation response to plant proximity, a role that can be considered dependent on the nucleocytoplasmic transport of macromolecules (i.e. is transport dependent). In addition, our results reveal a specific role for DRA2 in controlling shade-induced gene expression. We suggest that this novel regulatory role of DRA2 is transport independent and that it might rely on its dynamic localization within and outside of the NPC. These results provide mechanistic insights in to how SAS responses are rapidly established by light conditions. They also indicate that nucleoporins have an active role in plant signaling., M.G. received an FPI fellowship from the Spanish Ministerio de Economía y Competitividad (MINECO). A.G. and A.F.-A. received FPU fellowships from the Spanish Ministerio de Educación. S.P. received an FI fellowship from the Agència de Gestió D'ajuts Universitaris i de Recerca (AGAUR - Generalitat de Catalunya). C.T. received a Marie Curie IEF postdoctoral contract funded by the European Commission. I.R.-V. received initially an FPI fellowship from the Spanish MINECO and later a Beatriu de Pinós contract from AGAUR. Our research is supported by grants from the Spanish MINECO-FEDER [BIO2008-00169, BIO2011-23489 and BIO2014-59895-P] and Generalitat de Catalunya [2011-SGR447 and Xarba] to J.F.M.-G., and Generalitat Valenciana [PROMETEO/2009/112, PROMETEOII/2014/006] to M.R.P. and J.L.M. We acknowledge the support of the Spanish MINECO for the ‘Centro de Excelencia Severo Ochoa 2016-2019’ [award SEV-2015-0533].

En los laboratorios de Víctor Quesada y Pedro Robles se lleva a cabo una aproximación de genética inversa en la planta modelo Arabidopsis thaliana, con el fin de caracterizar genes nucleares no estudiados hasta el momento cuyos productos participan en la expresión de la información genética de los cloroplastos. Algunos de los genes que están siendo caracterizados codifican proteínas de los ribosomas cloroplásticos (clororribosomas), a los que hemos denominado CRD (CHLOROPLAST RIBOSOME DEFECTIVE). En este Trabajo Fin de Grado se ha iniciado la caracterización molecular y funcional de los genes CRD, centrándonos en CRD1 y CRD3. Con este objetivo, se ha determinado el efecto de la pérdida de su función sobre la expresión de algunos genes cloroplásticos y de otros nucleares, así como en los niveles de distintos tipos de ARN ribosómicos. Además, se han generado construcciones de sobreexpresión para realizar el rescate fenotípico de los mutantes crd y estudiar su efecto sobre el fenotipo silvestre. Adicionalmente, hemos identificado nuevos mutantes tras realizar una búsqueda de alelos insercionales de ADN‐T de genes nucleares que codifican proteínas del clororribosoma. Finalmente, se han realizado cruzamientos entre los mutantes crd y otros previamente descritos, afectados en la función de los clororribosomas, para estudiar sus eventuales interacciones genéticas mediante el análisis de dobles mutantes. A reverse genetics approach in the model plant Arabidopsis thaliana is taking place in the laboratories of Victor Quesada and Pedro Robles, with the aim of characterising nuclear genes so far unstudied and whose products are involved in the expression of the genetic information of the chloroplasts. One of the subjects of this study are the genes we have named CRD (CHLOROPLAST RIBOSOME DEFECTIVE), which encode proteins of the chloroplast ribosomes (chlororribosomes). In this Final Project, we have initiated the molecular and functional characterization of the CRD genes focusing on CRD1 and CRD3, because these genes have not been hitherto characterized. To this goal, the effect of their loss of function in the expression of some chloroplast and nuclear genes, as well as in the levels of various types of ribosomal RNAs has been determined. Furthermore, constructions overexpressing the CRD genes have been generated to carry out the phenotypic rescue of the crd mutants and to study their eventual effects on the wild‐type phenotype. In addition, we have identified new T‐DNA mutants after searching for insertional alleles of other nuclear genes encoding chlororribosome proteins. Finally, crosses between the crd mutants and others previously described and also affected in the chlororribosome function have been made, in order to study their potential genetic interactions by analysing the corresponding double mutants.