Search

No disponible.

Autophagy is a fast-moving field with an enormous impact on human health and disease. Understanding the complexity of the mechanism and regulation of this process often benefits from the use of simple experimental models such as the social amoeba Dictyostelium discoideum. Since the publication of the first review describing the potential of D. discoideum in autophagy, significant advances have been made that demonstrate both the experimental advantages and interest in using this model. Since our previous review, research in D. discoideum has shed light on the mechanisms that regulate autophagosome formation and contributed significantly to the study of autophagy-related pathologies. Here, we review these advances, as well as the current techniques to monitor autophagy in D. discoideum. The comprehensive bioinformatics search of autophagic proteins that was a substantial part of the previous review has not been revisited here except for those aspects that challenged previous predictions such as the composition of the Atg1 complex. In recent years our understanding of, and ability to investigate, autophagy in D. discoideum has evolved significantly and will surely enable and accelerate future research using this model.

ERECTA (ER) receptor-like kinase (RLK) regulates Arabidopsis thaliana organ growth, and inflorescence and stomatal development by interacting with the ERECTA-family genes (ERf) paralogs, ER-like 1 (ERL1) and ERL2, and the receptor-like protein (RLP) TOO MANY MOUTHS (TMM). ER also controls immune responses and resistance to pathogens such as the bacterium Pseudomonas syringae pv. tomato DC3000 (Pto) and the necrotrophic fungus Plectosphaerella cucumerina BMM (PcBMM). We found that er null-mutant plants overexpressing an ER dominant-negative version lacking the cytoplasmic kinase domain (ERΔK) showed an enhanced susceptibility to PcBMM, suggesting that ERΔK associates and forms inactive complexes with additional RLKs/RLPs required for PcBMM resistance. Genetic analyses demonstrated that ER acts in a combinatorial specific manner with ERL1, ERL2, and TMM to control PcBMM resistance. Moreover, BAK1 (BRASSINOSTEROID INSENSITIVE 1-associated kinase 1) RLK, which together with ERf/TMM regulates stomatal patterning and resistance to Pto, was also found to have an unequal contribution with ER in regulating immune responses and resistance to PcBMM. Co-immunoprecipitation experiments in Nicotiana benthamiana further demonstrated BAK1-ER protein interaction. The secreted epidermal pattern factor peptides (EPF1 and EPF2), which are perceived by ERf members to specify stomatal patterning, do not seem to regulate ER-mediated immunity to PcBMM, since their inducible overexpression in A. thaliana did not impact on PcBMM resistance. Our results indicate that the multiproteic receptorsome formed by ERf, TMM and BAK1 modulates A. thaliana resistance to PcBMM, and suggest that the cues underlying ERf/TMM/BAK1-mediated immune responses are distinct from those regulating stomatal pattering.

Dictyostelium es una ameba que vive en el suelo alimentándose de bacterias. Las señales de ausencia de nutrientes, desencadenan un complejo programa morfogenético que conlleva la formación de un cuerpo fructífero con dos tipos celulares perfectamente diferenciados, esporas y células tallo. La diferenciación de estos dos tipos celulares requiere una compleja regulación de rutas de señalización en las que diferentes señales (AMP cíclico, DIF-1, amonio) juegan un papel clave en la especificación de un tipo celular u otro. El AMPc, es esencial para el inicio del proceso de diferenciación y desarrollo. El morfógeno DIF-1, induce la diferenciación a células tallo y reprime la formación de esporas. El amonio, se genera como consecuencia de la intensa actividad metabólica y actúa como una base débil inhibiendo la diferenciación de ambos tipos celulares y regulando el inicio de la culminación (Stremcki et al., 2005; Williams, 2006). Este trabajo de tesis doctoral se ha basado en la caracterización genética y molecular de un mutante deficiente en la diferenciación de células tallo que hemos llamado, padA. El mutante fue aislado a partir de una genoteca, construída mediante la técnica REMI (Kuspa y Loomis, 1992), por su incapacidad para inducir la expresión del gen pretallo ecmB en presencia de DIF-1 (Sarafimidis, 2003). El mutante termosensible padA, recapitulado en el fondo silvestre, presenta una disrupción terminal en el gen padA que codifica una proteína truncada en la región carboxi-terminal. La proteína mantiene actividad residual a la temperatura óptima de crecimiento, 22ºC y carece de actividad a la temperatura restrictiva, 27ºC. La termosensibilidad del alelo padA nos permite estudiar las funciones de un gen esencial para el crecimiento y desarrollo de D. discoideum. El fenotipo del mutante padA es pleitrópico, a 22ºC, el crecimiento vegetativo es más lento y el desarrollo presenta un retraso general. A 27ºC, las amebas mutantes no son capaces de crecer en medio axén