PAMP-triggered immunity against Pseudomonas syringae involves microRNA-mediated regulation of several uncharacterized R genes

Two main types of noncoding small RNA molecules have been found in plants: microRNAs (miRNAs) and small interfering RNAs (siRNAs). They differ in their biogenesis and mode of action, but share similar sizes (20-24 nt). Their precursors are processed by Dicer-Like RNase III (dcl) proteins present in Arabidopsis thaliana, and in their mature form can act as negative regulators of gene expression, being involved in a vast array of plant processes, including plant development, genomic integrity or response to stress. Small-RNA mediated regulation can occurs at transcriptional level (TGS) or at post-transcriptional level (PTGS). In recent years, the role of gene silencing in the regulation of expression of genes related to plant defence responses against bacterial pathogens is becoming clearer. Comparisons carried out in our lab between the expression profiles of different mutants affected in gene silencing, and plants challenged with Pseudomonas syringae pathovar tomato DC3000, led us to identify a set of uncharacterized R genes, belonging to the TIR-NBS-LRR gene family, differentially expressed in these conditions. Through the use of bioinformatics tools, we found a miRNA* of 22 nt putatively responsible for down-regulating expression of these R genes through the generation of siRNAs. We have also found that the corresponding pri-miRNA is down-regulated after PAMP-perception in a SA-dependent manner. We also demonstrate that plants with altered levels of miRNA* (knockdown lines or overexpression lines) exhibit altered PTI-associated phenotypes, suggesting a role for this miRNA* in this defence response against bacteria. In addition we identify one of the target genes as a negative regulator of defence response against Pseudomonas syringae.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO, FEDE

Monte Carlo Analysis of GaN-Based Gunn Oscillators for Microwave Power Generation

Monte Carlo studies of transferred electron oscillators based on bulk wurtzite GaN are presented. Two structures have been examined: (i) devices with the conventional single notch structure, and (ii) repetitive structures with serial segments to fashion a multiple domain device. Wurtzite material has been chosen because of the higher drift velocity and because analytical expressions for the band structure have recently become available. Performance parameters of interest such as the operating frequency, output power, and conversion efficiency are calculated. Variations due to changes in temperature, biasing voltage, and device length are also included. It is shown that multidomain Gunn diodes can lead to significant improvements in output power over conventional, single-transit structure, and so such multiple GaN diodes merit serious experimental study

Tuning Proton Conductivity Properties of Lanthanide Amino-Sulfophosphonates-Loaded Nafion Composite Membranes

Polymer-based electrolytes in proton exchange membrane fuel cells (PEMFCs) utilize acidic groups as proton carriers and hydrogen bonding networks as proton-conducting pathways to facilitate proton transport. Crystalline acid-functionalized metal phosphonates are potential proton conductors while maintaining a high hydration degree below 100 °C. This property may be combined with Nafion-like polymers which tend to dehydrate at the operating conditions of PEMFCs [1,2]. In this work, preliminary results of the preparation of lanthanide amino-sulfophosphonates-loaded Nafion composites membranes and the corresponding electrical properties are reported. Synthesis conditions of lanthanide derivatives were optimized following a hightrough-put screening at 140 °C. Their crystal structures, solved from synchrotron X-ray powder diffraction data, corresponds to layered frameworks where the acidic groups, -CPO3H or -SO3H, point toward the interlamellar region interacting by H-bond with the lattice water. The composites were prepared by mixing the metal phosphonates with Nafion solution at different loadings. The membranes were characterized by SEM, XRD and FT-IR. A study of the proton conductivity as a function of the composite membranes was carried out at 90 °C and 95% RH. Referencias [1] Y. Gao, R. Broersen, W. Hageman, N. Yan, M. C. Mittelmeijer-Hazeleger, G. Rothenberg, S. Tanase. J. Mater. Chem. A, 2015, 3, 22347–22352. [2] A. Cabeza, P. Olivera-Pastor, R. M. P. Colodrero. Tailored Organic-Inorganic Materials, Brunet, E., Colón, J.L., Clearfield, A., Eds.; John Wiley & Sons, Inc. 2015; Ch. 4, 137−191.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Análisis del solapamiento funcional entre la respuesta de la planta frente a efectores secretados por Pseudomonas syringae y el silenciamiento génico

Las plantas están continuamente sometidas a infecciones por diferentes patógenos. Los patógenos bacterianos usan un complejo sistema de secreción para translocar proteínas efectoras al interior del huésped y suprimir así las respuestas de defensas. En los últimos años, se ha demostrado la participación de ciertos microRNAs en respuestas de defensas de la planta frente a patógenos bacterianos, así como la actuación de erectores bacterianos en rutas reguladas por miRNAs. Sin embargo poco se sabe acerca de cómo la regulación por microRNAs afecta a las respuestas de defensas de la planta frente a patógenos bacterianos, y de hecho menos es conocido sobre el impacto de la supresión de defensas mediada por efectores sobre las rutas reguladas por microRNAs. En este estudio, hemos realizado comparaciones entre análisis de microarrays, con el objetivo de diferenciar genes expresados diferencialmente (DEGs) en Arabidopsis, comunes entre la respuesta de defensa frente a efectores de Pseudomonas syringae y mutantes afectados en la biogénesis de miRNAs. El análisis de la anotación funcional de los DEGS comunes identificados, seguidos de un análisis de expresión mediante RT-qPCR nos ha servido para identificar procesos biológicos regulados por rutas de miRNAs en la interacción planta-patógenoUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Junta de Andalucía, Proyectos de Excelencia P06-CVI-02088; MINECO, Plan Nacional BIO2012-3564