The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance

Modélisation systémique de la dynamique de la ressource arborée en zone soudano-sahélienne. Le cas du territoire villageois de Mafa Kilda, Nord Cameroun

National audienceSystemic modelling firstly allows us to understand and identify the dynamics of a system. Mafa Kilda is a village whose inhabitants use a land shared by a number of different communities. Studies have shown that the strong pressure on woody resources requires appropriate steps to be taken in order to manage ligneous potential in a sustainable way. In order to enable population to understand and visualize the impacts of their actions on resources, Mafa Kilda's land system was studied and a computer model conceived accordingly. Different scenarios, developed in a participative manner during the course of a workshop, will be tested. The simulation results should provide a general survey of what resource evolution might be. Yet, these results must not be confused with reality, but compared with what it is known about it, in order to allow possible modifications of the initial system. Nevertheless, this model is a relevant tool to anticipate changes in the landscape and resources, according to the different management options selected. It constitutes a very useful tool in the respect of negociations concerning commun mana-gement of resources between farmers, stockbreeders and woodcutters. The same is true in so far as relations between stakeholders, natural resource managers, ecologists, scientist, policy makers, etc, are concerned.La modélisation systémique permet principalement de mieux comprendre et d'identifier les dynamiques d'un système. Mafa Kilda est un village dont les habitants utilisent un territoire partagé par différentes communautés. Des études y ont montré que la forte pression sur la ressource arborée nécessitait de prendre des dispositions adaptées à la situation pour gérer durablement le potentiel ligneux. Pour donner les moyens à la population de comprendre et de visualiser les impacts que ses actions peuvent avoir sur les ressources, le système du territoire de Mafa Kilda a été étudié et un modèle informatique est en construction. Différents scénarios, élaborés de manière participative au cours d`un atelier, seront testés. Les résultats de la simulation donneront un aperçu de ce que pourrait être l`évolution de la ressource sur le territoire. Cependant, ces résultats ne devront pas être confondus avec la réalité, mais comparés à ce que l`on sait d`elle, pour servir de base à une modification éventuelle du système. Ce modèle devrait ainsi constituer un outil intéressant pour appréhender l'évolution du paysage et des ressources de ce territoire, en fonction de différents choix de gestion qui pourraient être adoptés. Il trouverait sans doute sa place au sein de négociations concernant la gestion communautaire des ressources entre agriculteurs, éleveurs et bûcherons, mais aussi planificateurs, responsables de projets, agents des services forestiers, etc