Regulation of immunity during visceral Leishmania infection

Unicellular eukaryotes of the genus Leishmania are collectively responsible for a heterogeneous group of diseases known as leishmaniasis. The visceral form of leishmaniasis, caused by L. donovani or L. infantum, is a devastating condition, claiming 20,000 to 40,000 lives annually, with particular incidence in some of the poorest regions of the world. Immunity to Leishmania depends on the development of protective type I immune responses capable of activating infected phagocytes to kill intracellular amastigotes. However, despite the induction of protective responses, disease progresses due to a multitude of factors that impede an optimal response. These include the action of suppressive cytokines, exhaustion of specific T cells, loss of lymphoid tissue architecture and a defective humoral response. We will review how these responses are orchestrated during the course of infection, including both early and chronic stages, focusing on the spleen and the liver, which are the main target organs of visceral Leishmania in the host. A comprehensive understanding of the immune events that occur during visceral Leishmania infection is crucial for the implementation of immunotherapeutic approaches that complement the current anti-Leishmania chemotherapy and the development of effective vaccines to prevent disease.The research leading to these results has received funding from the European Community’s Seventh Framework Programme under grant agreement No.602773 (Project KINDRED). VR is supported by a post-doctoral fellowship granted by the KINDReD consortium. RS thanks the Foundation for Science and Technology (FCT) for an Investigator Grant (IF/00021/2014). This work was supported by grants to JE from ANR (LEISH-APO, France), Partenariat Hubert Curien (PHC) (program Volubilis, MA/11/262). JE acknowledges the support of the Canada Research Chair Program

Postfire Restoration of Soil Hydrology and Wildland Vegetation Using Surfactant Seed Coating Technology

In semiarid environments, soil water repellency can contribute to reseeding failure by reducing soil moisture availability. Nonionic soil surfactants (wetting agents) have been shown to be effective in enhancing infiltration and improving root-zone water reserves in water-repellent soils. However, the application of soil surfactants in wildland ecosystems can be logistically and economically prohibitive. In this study, we evaluated a potential solution for applying soil surfactants using seed coating technology. Through this technology, the seed is used as a carrier for the soil surfactant. After planting, water transfers the surfactant from the seed into the soil where it ameliorates the water repellency within the seed’s microsite. The objectives of this research were 1) to establish the efficacy of a surfactant seed coating (SSC) in ameliorating soil water repellency, and 2) to determine the influence of SSC on seedling emergence and plant survival. To accomplish the first objective, detailed soil column experiments were conducted in the laboratory on water-repellent soil obtained from a burned pinyon-juniper (Pinus-Juniperus spp.) woodland. The second objective was met through greenhouse testing of SSC applied to crested wheatgrass and bluebunch wheatgrass seed, using the same soil as used in the first objective. Results indicate that SSC increased soilwater infiltration, percolation, and retention. This technology had no influence on seedling emergence for crested wheatgrass, but SSC improved bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] Á. Löve) emergence threefold. Plant survival was dramatically improved by the SSC. Only 0.75%of the seedlings that grew from noncoated seed survived to the end of the study, whereas 37% of the plants survived in the SSC treatment. Overall, these results indicate that it may be plausible for SSC to improve postfire restoration efforts by restoring soil hydrologic function and increasing seedling emergence and early seedling development./En las zonas semiáridas, la repelencia del agua del suelo puede contribuir a las fallas de las resiembras reduciendo la disponibilidad de la humedad del suelo. Los surfactantes no iónicos del suelo (agentes de adherencia) han demostrado ser eficaces en ayudar la infiltración y mejorar las reservas de agua de la zona de la raíz en suelos impermeables. Sin embargo, el uso de surfactantes en suelos de ecosistemas de pastizales puede ser logísticamente y económicamente prohibitivo. En este estudio evaluamos una solución viable para aplicar los surfactantes del suelo usando tecnología para cubrir la semilla. Con esta tecnología la semilla se utiliza como portador para el surfactante del suelo. Después de ser plantada, el agua transfiere el surfactante de la semilla en el suelo donde mejora la repelencia del agua dentro del micro-sitio de la semilla. Los objetivos de esta investigación fueron 1) establecer la eficiencia de una cubierta en la semilla del surfactante (SSC) en el mejoramiento de repelencia del agua del suelo, y 2) determinar la influencia de SSC en la aparición de las plántulas y la sobrevivencia de las plantas. Para llevar a cabo el primer objetivo, se realizaron experimentos detallados en columnas de suelos en el laboratorio utilizando suelo impermeable obtenido de una área quemada de piñón-junípero. El segundo objetivo fue resuelto en pruebas de SSC conducidas en el invernadero aplicadas a semillas de triguillo crestado y bluebunch wheatgrass usando el mismo suelo del objetivo1. Los resultados indican que SSC aumentó la infiltración, la percolación, y la retención del agua del suelo. Esta tecnología no tiene ningún efecto en la aparición de las plántulas de triguillo crestado pero SSC mejoró triple la aparición del bluebunch wheatgrass. La sobrevivencia de las plantas fue mejorada dramáticamente por el SSC. Solamente el 0.75% de las plántulas que crecieron de la semilla no-revestida sobrevivieron al final del estudio, mientras que el 37% de las plantas sobrevivieron en el tratamiento de SSC. En general, estos resultados indican que puede posible que SSC mejore los esfuerzos de la restauración después de las quemas restaurando la función hidrológica del suelo y aumentando la aparición de la plántula, así como desarrollo más rápido de las mismas plántulas.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Engineering Rhizosphere Hydraulics: Pathways to Improve Plant Adaptation to Drought

Recent studies have drawn attention to the role of mucilage in shaping rhizosphere hydraulic properties and regulating root water uptake. During drying, mucilage keeps the rhizosphere wet and conductive, but on drying it turns hydrophobic, limiting root water uptake. In this study, we introduce the concept of , defined as additives that (i) rewet the rhizosphere and (ii) reduce mucilage swelling, thereby reducing the rhizosphere conductivity. We tested whether selected surfactants behaved as rhizoligands. We used neutron radiography to monitor water redistribution in the rhizosphere of lupine ( L. cv. Feodora) and maize ( L.) irrigated with water and rhizoligands. In a parallel experiment, we tested the effect of rhizoligands on the transpiration rate of lupine and maize subjected to repeated drying and wetting cycles. We also measured the effect of rhizoligands on the maximum swelling of mucilage and the saturated hydraulic conductivity of soil mixed with various mucilage concentrations. Rhizoligand treatment quickly and uniformly rewetted the rhizosphere of maize and lupine. Interestingly, rhizoligands also reduced transpiration during drying–wetting cycles. Our hypothesis is that the reduction in transpiration was triggered by the interaction between rhizoligand and mucilage exuded by roots. This hypothesis is supported by the fact that rhizoligand reduced the maximum swelling of mucilage, increased its viscosity, and decreased the hydraulic conductivity of soil–mucilage mixtures. The reduced conductivity of the rhizosphere induced a moderate stress to the plants, reducing transpiration. Rhizoligands increase the rhizosphere wetting kinetics and decrease the maximum swelling of mucilage. As a consequence, root rehydration following irrigation is faster, a larger volume of water is available to the plant, and this water is used more slowly. This slower water consumption would allow the plant to stay turgid during a prolonged drying period. We propose that by managing the hydraulic properties of the rhizosphere, we can improve plants’ adaptation to drought