Application of Ultraintense Lasers to validate materials for laser fusion: production of ions and other relevant species

Justification of the need and demand of experimental facilities to test and validate materials for first wall in laser fusion reactors - Characteristics of the laser fusion products - Current ?possible? facilities for tests Ultraintense Lasers as ?complete? solution facility - Generation of ion pulses - Generation of X-ray pulses - Generation of other relevant particles (electrons, neutrons..)

Plasma���wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials

Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong bursts of fast charged particles which will deposit tens of kJ m���2 and implant more than 1018 particles m���2 in a few microseconds at a repetition rate of some Hz. Large chamber dimensions and resistant plasma-facing materials must be combined to guarantee the chamber performance as long as possible under the expected threats: heating, fatigue, cracking, formation of defects, retention of light species, swelling and erosion. Current and novel radiation resistant materials for the first wall need to be validated under realistic conditions. However, at present there is a lack of facilities which can reproduce such ion environments. This contribution proposes the use of ultra-intense lasers and high-intense pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By target normal sheath acceleration, ultra-intense lasers can generate very short and energetic ion pulses with a spectral distribution similar to that of the inertial fusion ion bursts, suitable to validate fusion materials and to investigate the barely known propagation of those bursts through background plasmas/gases present in the reactor chamber. HIPIB technologies, initially developed for inertial fusion driver systems, provide huge intensity pulses which meet the irradiation conditions expected in the first wall of LIF chambers and thus can be used for the validation of materials too.

Plasma���wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials

Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong bursts of fast charged particles which will deposit tens of kJ m���2 and implant more than 1018 particles m���2 in a few microseconds at a repetition rate of some Hz. Large chamber dimensions and resistant plasma-facing materials must be combined to guarantee the chamber performance as long as possible under the expected threats: heating, fatigue, cracking, formation of defects, retention of light species, swelling and erosion. Current and novel radiation resistant materials for the first wall need to be validated under realistic conditions. However, at present there is a lack of facilities which can reproduce such ion environments. This contribution proposes the use of ultra-intense lasers and high-intense pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By target normal sheath acceleration, ultra-intense lasers can generate very short and energetic ion pulses with a spectral distribution similar to that of the inertial fusion ion bursts, suitable to validate fusion materials and to investigate the barely known propagation of those bursts through background plasmas/gases present in the reactor chamber. HIPIB technologies, initially developed for inertial fusion driver systems, provide huge intensity pulses which meet the irradiation conditions expected in the first wall of LIF chambers and thus can be used for the validation of materials too.

Transcriptional changes and oxidative stress associated with the synergistic interaction between potato virus X and potato virus Y and their relationship with symptom expression.

Many virus diseases of economic importance to agriculture result from mixtures of different pathogens invading the host at a given time. This contrasts with the relatively scarce studies available on the molecular events associated with virus---host interactions in mixed infections. Compared with single infections, co-infection of Nicotiana benthamiana with Potato virus X (PVX) and Potato virus Y (PVY) resulted in increased systemic symptoms (synergism) that led to necrosis of the newly emerging leaves and death of the plant. A comparative transcriptional analysis was undertaken to identify quantitative and qualitative differences in gene expression during this synergistic infection and correlate these changes with the severe symptoms it caused. Global transcription profiles of doubly infected leaves were compared with those from singly infected leaves using gene ontology enrichment analysis and metabolic pathway annotator software. Functional gene categories altered by the double infection comprise suites of genes regulated coordinately, which are associated with chloroplast functions (downregulated), protein synthesis and degradation (upregulated), carbohydrate metabolism (upregulated), and response to biotic stimulus and stress (upregulated). The expressions of reactive oxygen species?generating enzymes as well as several mitogen-activated protein kinases were also significantly induced. Accordingly, synergistic infection induced a severe oxidative stress in N. benthamiana leaves, as judged by increases in lipid peroxidation and by the generation of superoxide radicals in chloroplasts, which correlated with the misregulation of antioxidative genes in microarray data. Interestingly, expression of genes encoding oxylipin biosynthesis was uniquely upregulated by the synergistic infection. Virus-induced gene silencing of ?-dioxygenase1 delayed cell death during PVX?PVY infection.

New insights into the regulation of NADPH oxidase dependent reactive oxygen species signaling during the plant immune response

Las NADPH oxidasas de plantas, denominadas ���respiratory burst oxidase homologues��� (RBOHs), producen especies reactivas del ox��geno (ROS) que median un amplio rango de funciones. En la c��lula vegetal, el ajuste preciso de la producci��n de ROS aporta la especificidad de se��al para generar una respuesta apropiada ante las amenazas ambientales. RbohD y RbohF, dos de los diez genes Rboh de Arabidopsis, son pleiotr��picos y median diversos procesos fisiol��gicos en respuesta a pat��genos. El control espacio-temporal de la expresi��n de los genes RbohD y RbohF podr��a ser un aspecto cr��tico para determinar la multiplicidad de funciones de estas oxidasas. Por ello, generamos l��neas transg��nicas de Arabidopsis con fusiones de los promoters de RbohD y RbohF a los genes delatores de la B-glucuronidasa y la luciferasa. Estas l��neas fueron empleadas para revelar el patr��n de expresi��n diferencial de RbohD y RbohF durante la respuesta inmune de Arabidopsis a la bacteria pat��gena Pseudomonas syringae pv. tomato DC3000, el hongo necr��trofo Plectosphaerella cucumerina y en respuesta a se��ales relacionadas con la respuesta inmune. Nuestros experimentos revelan un patr��n de expresi��n diferencial de los promotores de RbohD y RbohF durante el desarrollo de la planta y en la respuesta inmune de Arabidopsis. Adem��s hemos puesto de manifiesto que existe una correlaci��n entre el nivel de actividad de los promotores de RbohD y RbohF con la acumulaci��n de ROS y el nivel de muerte celular en respuesta a pat��genos. La expression de RbohD y RbohF tambi��n es modulada de manera diferencial en respuesta a patrones moleculares asociados a pat��genos (PAMPs) y por ��cido absc��sico (ABA). Cabe destacar que, mediante una estrategia de intercambio de promotores, hemos revelado que la regi��n promotora de RbohD, es necesaria para dirigir la producci��n de ROS en respuesta a P. cucumerina. Adicionalmente, la activaci��n del promotor de RbohD en respuesta al aislado de P. cucumerina no adaptado a Arabidopsis 2127, nos llev�� a realizar ensayos de susceptibilidad con el doble mutante rbohD rbohF que han revelado un papel desconocido de estas oxidasas en resistencia no-huesped. La interacci��n entre la se��alizaci��n dependiente de las RBOHs y otros componentes de la respuesta inmune de plantas podr��a explicar tambi��n las distintas funciones que median estas oxidasas en relaci��n con la respuesta inmune. Entre la gran cantidad de se��ales coordinadas con la actividad de las RBOHs, existen evidencias gen��ticas y farmacol��gicas que indican que las prote��nas G heterotrim��ricas est��n implicadas en algunas de las rutas de se��alizaci��n mediadas por ROS derivadas de los RBOHs en respuesta a se��ales ambientales. Por ello hemos estudiado la relaci��n entre estas RBOH-NADPH oxidasas y AGB1, la subunidad �� de las prote��nas G heterotrim��ricas en la respuesta inmune de Arabidopsis. An��lisis de epistasis indican que las prote��nas G heterotrim��ricas est��n implicadas en distintas rutas de se��alizaci��n en defensa mediadas por las RBOHs. Nuestros resultados ilustran la relaci��n compleja entre la se��alizaci��n mediada por las RBOHs y las prote��nas G heterotrim��ricas, que var��a en funci��n de la interacci��n planta-pat��geno analizada. Adem��s, hemos explorado la posible asociaci��n entre AGB1 con RBOHD y RBOHF en eventos tempranos de la respuesta immune. Cabe se��alar que experimentos de co��mmunoprecipitaci��n apuntan a una posible asociaci��n entre AGB1 y la kinasa citoplasm��tica reguladora de RBOHD, BIK1. Esto indica un posible mecanismo de control de la funci��n de esta NADPH oxidase por AGB1. En conjunto, estos datos aportan nuevas perspectivas sobre c��mo, a trav��s del control transcripcional o mediante la interacci��n con las prote��nas G heterotrim��ricas, las NADPH oxidases de plantas median la producci��n de ROS y la se��alizaci��n por ROS en la respuesta inmune. Nuestro trabajo ejemplifica c��mo la regulaci��n diferencial de dos miembros de una familia multig��nica, les permite realizar distintas funciones fisiol��gicas especializadas usando un mismo mecanismo enzim��tico. ABSTRACT The plant NADPH oxidases, termed respiratory burst oxidase homologues (RBOHs), produce reactive oxygen species (ROS) which mediate a wide range of functions. Fine tuning this ROS production provides the signaling specificity to the plant cell to produce the appropriate response to environmental threats. RbohD and RbohF, two of the ten Rboh genes present in Arabidopsis, are pleiotropic and mediate diverse physiological processes in response to pathogens. One aspect that may prove critical to determine the multiplicity of functions of RbohD and RbohF is the spatio-temporal control of their gene expression. Thus, we generated Arabidopsis transgenic lines with RbohD- and RbohF-promoter fusions to the ��-glucuronidase and the luciferase reporter genes. These transgenics were employed to reveal RbohD and RbohF promoter activity during Arabidopsis immune response to the pathogenic bacterium Pseudomonas syringae pv tomato DC3000, the necrotrophic fungus Plectosphaerella cucumerina and in response to immunity-related cues. Our experiments revealed a differential expression pattern of RbohD and RbohF throughout plant development and during Arabidopsis immune response. Moreover, we observed a correlation between the level of RbohD and RbohF promoter activity, the accumulation of ROS and the amount of cell death in response to pathogens. RbohD and RbohF gene expression was also differentially modulated by pathogen associated molecular patterns and abscisic acid. Interestingly, a promoter-swap strategy revealed the requirement for the promoter region of RbohD to drive the production of ROS in response to P. cucumerina. Additionally, since the RbohD promoter was activated during Arabidopsis interaction with a non-adapted P. cucumerina isolate 2127, we performed susceptibility tests to this fungal isolate that uncovered a new role of these oxidases on non-host resistance. The interplay between RBOH-dependent signaling with other components of the plant immune response might also explain the different immunity-related functions mediated by these oxidases. Among the plethora of signals coordinated with RBOH activity, pharmacological and genetic evidence indicates that heterotrimeric G proteins are involved in some of the signaling pathways mediated by RBOH���derived ROS in response to environmental cues. Therefore, we analysed the interplay between these RBOH-NADPH oxidases and AGB1, the Arabidopsis ��-subunit of heterotrimeric G proteins during Arabidopsis immune response. We carried out epistasis studies that allowed us to test the implication of AGB1 in different RBOH-mediated defense signaling pathways. Our results illustrate the complex relationship between RBOH and heterotrimeric G proteins signaling, that varies depending on the type of plant-pathogen interaction. Furthermore, we tested the potential association between AGB1 with RBOHD and RBOHF during early immunity. Interestingly, our co-immunoprecipitation experiments point towards an association of AGB1 and the RBOHD regulatory kinase BIK1, thus providing a putative mechanism in the control of the NADPH oxidase function by AGB1. Taken all together, these studies provide further insights into the role that transcriptional control or the interaction with heterotrimeric G-proteins have on RBOH-NADPH oxidase-dependent ROS production and signaling in immunity. Our work exemplifies how, through a differential regulation, two members of a multigenic family achieve specialized physiological functions using a common enzymatic mechanism.