A network of stress-related genes regulates hypocotyl elongation downstream of selective auxin perception

The plant hormone auxin, a master coordinator of development, regulates hypocotyl elongation during seedling growth. We previously identified the synthetic molecule RubNeddin 1 (RN1), which induces degradation of the AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) transcriptional repressors INDOLE-3-ACETIC ACID-INDUCIBLE3 (IAA3) and IAA7 in planta and strongly promotes hypocotyl elongation. In the present study, we show that despite the structural similarity of RN1 to the synthetic auxin 2,4-dichlorophenoxyacetic-acid (2,4-D), direct treatments with these compounds in Arabidopsis (Arabidopsis thaliana) result in distinct effects, possibly due to enhanced uptake of RN1 and low-level, chronic release of 2,4-D from RN1 in planta. We confirm RN1-induced hypocotyl elongation occurs via specific TRANSPORT INHIBITOR RESISTANT1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) receptor-mediated auxin signaling involving TIR1, AFB2, and AFB5. Using a transcriptome profiling strategy and candidate gene approach, we identify the genes ZINC FINGER OF ARABIDOPSIS THALIANA10 (ZAT10), ARABIDOPSIS TOXICOS EN LEVADURA31 (ATL31), and WRKY DNA-BINDING PROTEIN33 (WRKY33) as being rapidly upregulated by RN1, despite being downregulated by 2,4-D treatment. RN1-induced expression of these genes also occurs via TIR1/AFB-mediated auxin signaling. Our results suggest both hypocotyl elongation and transcription of these genes are induced by RN1 via the promoted degradation of the AUX/IAA transcriptional repressor IAA7. Moreover, these three genes, which are known to be stress-related, act in an inter-dependent transcriptional regulatory network controlling hypocotyl elongation. Together, our results suggest ZAT10, ATL31, and WRKY33 take part in a common gene network regulating hypocotyl elongation in Arabidopsis downstream of a selective auxin perception module likely involving TIR1, AFB2, and AFB5 and inducing the degradation of IAA7

Global Island Monitoring Scheme (GIMS) : a proposal for the long-term coordinated survey and monitoring of native island forest biota

Islands harbour evolutionary and ecologically unique biota, which are currently disproportionately threatened by a multitude of anthropogenic factors, including habitat loss, invasive species and climate change. Native forests on oceanic islands are important refugia for endemic species, many of which are rare and highly threatened. Long-term monitoring schemes for those biota and ecosystems are urgently needed: (i) to provide quantitative baselines for detecting changes within island ecosystems, (ii) to evaluate the effectiveness of conservation and management actions, and (iii) to identify general ecological patterns and processes using multiple island systems as repeated 'natural experiments'. In this contribution, we call for a Global Island Monitoring Scheme (GIMS) for monitoring the remaining native island forests, using bryophytes, vascular plants, selected groups of arthropods and vertebrates as model taxa. As a basis for the GIMS, we also present new, optimized monitoring protocols for bryophytes and arthropods that were developed based on former standardized inventory protocols. Effective inventorying and monitoring of native island forests will require: (i) permanent plots covering diverse ecological gradients (e.g. elevation, age of terrain, anthropogenic disturbance); (ii) a multiple-taxa approach that is based on standardized and replicable protocols; (iii) a common set of indicator taxa and community properties that are indicative of native island forests' welfare, building on, and harmonized with existing sampling and monitoring efforts; (iv) capacity building and training of local researchers, collaboration and continuous dialogue with local stakeholders; and (v) long-term commitment by funding agencies to maintain a global network of native island forest monitoring plots.Peer reviewe

Analyse des méthodes itératives par points pour les problèmes de diffusion-convection approchés par les schémas compacts

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

LA METHODE SEMI-LAGRANGIENNE A DEUX PAS DE TEMPS APPLIQUEE A UN MODELE DE PREVISION ATMOSPHERIQUE (AMELIORATION DE LA CONSERVATION ET DE LA STABILITE)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Role of TolR N-Terminal, Central, and C-Terminal Domains in Dimerization and Interaction with TolA and TolQ

The Tol-PAL system of Escherichia coli is a multiprotein system involved in maintaining the cell envelope integrity and is necessary for the import of some colicins and phage DNA into the bacterium. It is organized into two complexes, one near the outer membrane between TolB and PAL and one in the cytoplasmic membrane between TolA, TolQ, and TolR. In the cytoplasmic membrane, all of the Tol proteins have been shown to interact with each other. Cross-linking experiments have shown that the TolA transmembrane domain interacts with TolQ and TolR. Suppressor mutant analyses have localized the TolQ-TolA interaction to the first transmembrane domain of TolQ and have shown that the third transmembrane domain of TolQ interacts with the transmembrane domain of TolR. To get insights on the composition of the cytoplasmic membrane complex and its possible contacts with the outer membrane complex, we focused our attention on TolR. Cross-linking and immunoprecipitation experiments allowed the identification of Tol proteins interacting with TolR. The interactions of TolR with TolA and TolQ were confirmed, TolR was shown to dimerize, and the resulting dimer was shown to interact with TolQ. Deletion mutants of TolR were constructed, and they allowed us to determine the TolR domains involved in each interaction. The TolR transmembrane domain was shown to be involved in the TolA-TolR and TolQ-TolR interactions, while TolR central and C-terminal domains appeared to be involved in TolR dimerization. The role of the TolR C-terminal domain in the TolA-TolR interaction and its association with the membranes was also demonstrated. Furthermore, phenotypic studies clearly showed that the three TolR domains (N terminal, central, and C terminal) and the level of TolR production are important for colicin A import and for the maintenance of cell envelope integrity

Considérations sur l'approche européenne d'acceptabilité des matériaux au contact des eaux de consommation humaine

Les constituants des matériaux au contact des eaux de consommation humaine peuvent migrer dans l'eau et altérer ses propriétés organoleptiques, physico-chimiques et microbiologiques. Des essais préalables doivent permettre de vérifier leur inertie ; cependant, les résultats d'analyses en laboratoire ne peuvent refléter la réalité d'un réseau, celui-ci étant constitué d'un ensemble d'éléments divers dont les comportements et les fonctions sont variables dans le temps et l'espace. Afin d'harmoniser les réglementations existantes et éviter les entraves techniques au libre échange entre les Etats membres, la Commission européenne a entrepris des travaux dans deux directions : elle a chargé le Comité européen de normalisation d'élaborer des méthodes d'essais harmonisée (échantillonnage, conditions opératoires) et confié au Groupe des Réglementeurs des produits de construction en contact avec l'eau potable (GR-PCEP) la définition les critères d'acceptabilité. L'élaboration de ces critères se heurte à certaines difficultés de modélisation du réseau pour en déduire le comportement du matériau dans cet ensemble. Les facteurs de conversion ont été introduits pour permettre une base de comparaison par rapport à des référentiels connus ; celui de la directive 98/83/CE pour l'eau de consommation humaine et celui de la directive 90/128/CE pour les matériaux au contact alimentaire. Si les grandes lignes sont d'ores et déjà fixées, bien des incertitudes demeurent encore qui font l'objet de discussions internationales. Les travaux qui ont été entrepris s'inspirent des approches françaises et doivent s'achever au plus tard en 2004/2005 du fait de leur complexité sur une certification des matériaux et un marquage spécifique pour l'eau de boisson « CE-EAS »