Search

International audience; The major intrinsic protein (MIP) superfamily is a key part of the fungal transmembrane transport network. It facilitates the transport of water and low molecular weight solutes across biomembranes. The fungal uncharacterized X-Intrinsic Protein (XIP) subfamily includes the full protein diversity of MIP. Their biological functions still remain fully hypothetical. The aim of this study is still to deepen the diversity and the structure of the XIP subfamily in light of the MIP counterparts—the aquaporins (AQPs) and aquaglyceroporins (AQGPs)—and to describe for the first time their function in the development, biomass accumulation, and mycoparasitic aptitudes of the fungal bioagent Trichoderma atroviride. The fungus-XIP clade, with one member (TriatXIP), is one of the three clades of MIPs that make up the diversity of T. atroviride MIPs, along with the AQPs (three members) and the AQGPs (three members). TriatXIP resembles those of strict aquaporins, predicting water diffusion and possibly other small polar solutes due to particularly wider ar/R constriction with a Lysine substitution at the LE2 position. The XIP loss of function in ΔTriatXIP mutants slightly delays biomass accumulation but does not impact mycoparasitic activities. ΔTriatMIP forms colonies similar to wild type; however, the hyphae are slightly thinner and colonies produce rare chlamydospores in PDA and specific media, most of which are relatively small and exhibit abnormal morphologies. To better understand the molecular causes of these deviant phenotypes, a wide-metabolic survey of the ΔTriatXIPs demonstrates that the delayed growth kinetic, correlated to a decrease in respiration rate, is caused by perturbations in the pentose phosphate pathway. Furthermore, the null expression of the XIP gene strongly impacts the expression of four expressed MIPencoding genes of T. atroviride, a plausible compensating effect which safeguards the physiological integrity and life cycle of the fungus. This paper offers an overview of the fungal XIP family in the biocontrol agent T. atroviride which will be useful for further functional analysis of this particular MIP subfamily in vegetative growth and the environmental stress response in fungi. Ultimately, these findings have implications for the ecophysiology of Trichoderma spp. in natural, agronomic, and industrial systems.

Of 13 onion cultivars, red onions had longer storage life than white onions. Storage life was correlated with dry matter content. Botrytis spp., Aspergillus spp., Fusarium oxysporum and Penicillium spp. were frequently isolated from rotted bulbs. Fusarium oxysporum pathogenicity tested on healthy bulbs led to a typical basal rot; this is the first report of Fusarium oxysporum f.sp. cepae in Tunisia. Copyright © 2006 John Wiley & Sons, Ltd

Seven simple and advanced dynamic polymorphic functions were considered to develop a dominant height growth model for Spanish and Tunisian cork oak forests. Data from 115 stem analyses performed in two regions in each country were used to fit the equations. Parameter estimates were obtained using the Dummy variable method. Both numerical, graphical and biological consistency were used to compare alternative models. The dynamic equation finally selected was derived from the Hossfeld model by considering the shape parameter to be related to site productivity. An analysis of the dominant height growth patterns between the two countries indicated that the same dominant height growth model was valid for both countries. This dominant height growth model allows estimation of dominant height with a level of reliability of at least 83% from an age of 15 years for a prediction interval of less than 40 years., Para desarrollar un modelo de crecimiento en altura dominante para monte alcornocal en España y Túnez se han probado siete funciones polimórficas simples y dinámicas. Para ello se han utilizado datos procedentes de 115 análisis de troncos realizados en dos regiones distintas de cada país. Para estimar los parámetros se utilizó el método de las variables ficticias. Los modelos fueron comparados de forma numérica y gráfica. La ecuación dinámica finalmente seleccionada fue derivada a partir de la ecuación de crecimiento de Hossfeld considerando el parámetro de forma como relacionado con la productividad de la estación. El análisis del patrón que sigue el crecimiento en altura dominante en ambos países indica que el mismo modelo de crecimiento en altura dominante es valido para ambos países. Este modelo de crecimiento en altura dominante nos permite estimar la altura dominante con una fiabilidad de más de un 83% a partir de los 15 años para un periodo de predicción menor de 40 años.

Les semis, les plantations, les rejets de souche après recépage peuvent reconstituer la couverture ligneuse. Parfois, les deux premières techniques s'avèrent inefficaces et coûteuses. Le marcottage naturel et le drageonnage constituent une quatrième voie très économique. En régions semi-arides, il est impératif de faire apparaître les connaissances traditionnelles relatives aux techniques de propagation végétative naturelle et de lancer des études sur des espèces-clés montrant cette aptitude à se réitérer. (Texte intégral)