Identification and characterization of "rd22" dehydration responsive gene in grapevine (Vitis vinifera L.)

To identify and isolate genes related to abiotic stresses (salinity and drought) tolerance in grapevine, a candidate gene approach was developed and allowed isolating a full-length cDNA of rd22 gene from the Cabernet Sauvignon variety. The latter, named Vvrd22, is a dehydration-responsive gene that is usually induced by the application of exogenous ABA. Details of the physicochemical parameters and structural properties (molecular mass, secondary structure, conserved domains and motives, putative post-translational modification sites...) of the encoded protein have also been elucidated. The expression study of Vvrd22 was carried out at the berry growth stages and at the level of plant organs and tissues as well as under both drought and salt stresses. The results showed that Vvrd22 is constitutively expressed at a low level in all analyzed tissues. Moreover, salt stress induced Vvrd22 expression, particularly for the tolerant variety (Razegui), contrary to the sensitive one (Syrah), which did not display any expression variation during the stress, which means that Vvrd22 is involved in salt stress response and that its expression level depends on regulatory mechanisms that are efficient only for the tolerant variety. On the other hand, under drought stress, Vvrd22 is induced in an identical manner for both tolerant and sensitive varieties. In addition, stress signal molecules such as ABA (lonely applied or in combination with sucrose) induced Vvrd22 expression, even at a low level. A minimal knowledge about the role and the functionality of this gene is necessary and constitutes a prerequisite condition before starting and including Vvrd22 in any program of improvement of grapevine's abiotic stress tolerance.     

Muscle dystroglycan organizes the postsynapse and regulates presynaptic neurotransmitter release at the Drosophila neuromuscular junction

Background

The Dystrophin-glycoprotein complex (DGC) comprises dystrophin, dystroglycan, sarcoglycan, dystrobrevin and syntrophin subunits. In muscle fibers, it is thought to provide an essential mechanical link between the intracellular cytoskeleton and the extracellular matrix and to protect the sarcolemma during muscle contraction. Mutations affecting the DGC cause muscular dystrophies. Most members of the DGC are also concentrated at the neuromuscular junction (NMJ), where their deficiency is often associated with NMJ structural defects. Hence, synaptic dysfunction may also intervene in the pathology of dystrophic muscles. Dystroglycan is a central component of the DGC because it establishes a link between the extracellular matrix and Dystrophin. In this study, we focused on the synaptic role of Dystroglycan (Dg) in Drosophila.

Methodology/Principal Findings

We show that Dg was concentrated postsynaptically at the glutamatergic NMJ, where, like in vertebrates, it controls the concentration of synaptic Laminin and Dystrophin homologues. We also found that synaptic Dg controlled the amount of postsynaptic 4.1 protein Coracle and alpha-Spectrin, as well as the relative subunit composition of glutamate receptors. In addition, both Dystrophin and Coracle were required for normal Dg concentration at the synapse. In electrophysiological recordings, loss of postsynaptic Dg did not affect postsynaptic response, but, surprisingly, led to a decrease in glutamate release from the presynaptic site.

Conclusion/Significance

Altogether, our study illustrates a conservation of DGC composition and interactions between Drosophila and vertebrates at the synapse, highlights new proteins associated with this complex and suggests an unsuspected trans-synaptic function of Dg.     

Ant-based swarming with positionless micro air vehicles for communication relay

Swarming without positioning information is interesting in application-oriented systems because it alleviates the need for sensors which are dependent on the environment, expensive in terms of energy, cost, size and weight, or unusable at useful ranges for real-life scenarios. This principle is applied to the development of a swarm of micro air vehicles (SMAVs) for the deployment of ad hoc wireless communication networks (SMAVNETs) between ground users in disaster areas. Rather than relying on positioning information, MAVs rely on local communication with immediate neighbors and proprioceptive sensors which provide heading, speed and altitude. To solve the challenging task of designing agent controllers to achieve the swarm behavior of the SMAVNET, inspiration is taken from army ants which are capable of laying and maintaining pheromone paths leading from their nest to food sources in nature. This is analogous to the deployment of communication pathways between multiple ground users. However, instead of being physically deposited in the air or on a map, pheromone is virtually deposited on the MAVs using local communication. This approach is investigated in 3D simulation in a simplified scenario with two ground users.     

Interaction of the RAGE cytoplasmic domain with diaphanous-1 is required for ligand-stimulated cellular migration through activation of Rac1 and Cdc42

Cellular migration is a fundamental process linked to diverse pathological states such as diabetes and its complications, atherosclerosis, inflammation, and cancer. The receptor for advanced glycation end products (RAGE) is a multiligand cell surface macromolecule which binds distinct ligands that accumulate in these settings. RAGE-ligand interaction evokes central changes in key biological properties of cells, including proliferation, generation of inflammatory mediators, and migration. Although RAGE-dependent signal transduction is critically dependent on its short cytoplasmic domain, to date the proximate mechanism by which this RAGE domain engages and stimulates cytoplasmic signaling pathways has yet to be identified. Here we show that the RAGE cytoplasmic domain interacts with Diaphanous-1 (Dia-1) both in vitro and in vivo. We employed the human RAGE cytoplasmic domain as "bait" in the yeast two-hybrid assay and identified the formin homology (FH1) domain of Dia-1 as a potential binding partner of this RAGE domain. Immunoprecipitation studies revealed that the RAGE cytoplasmic domain interacts with the FH1 domain of Dia-1. Down-regulation of Dia-1 expression by RNA interference blocks RAGE-mediated activation of Rac-1 and Cdc42 and, in parallel, RAGE ligand-stimulated cellular migration. Taken together, these findings indicate that the interaction of the RAGE cytoplasmic domain with Dia-1 is required to transduce extracellular environmental cues evoked by binding of RAGE ligands to their cell surface receptor, a chief consequence of which is Rac-1 and Cdc42 activation and cellular migration. Because RAGE and Dia-1 are implicated in the regulation of inflammatory, vascular, and transformed cell migration, these findings highlight this interaction as a novel target for therapeutic intervention in inflammation, atherosclerosis, diabetes, and cancer.     

Pleiotropy in the melanocortin system, coloration and behavioural syndromes

In vertebrates, melanin-based coloration is often associated with variation in physiological and behavioural traits. We propose that this association stems from pleiotropic effects of the genes regulating the synthesis of brown to black eumelanin. The most important regulators are the melanocortin 1 receptor and its ligands, the melanocortin agonists and the agouti-signalling protein antagonist. On the basis of the physiological and behavioural functions of the melanocortins, we predict five categories of traits correlated with melanin-based coloration. A review of the literature indeed reveals that, as predicted, darker wild vertebrates are more aggressive, sexually active and resistant to stress than lighter individuals. Pleiotropic effects of the melanocortins might thus account for the widespread covariance between melanin-based coloration and other phenotypic traits in vertebrates.     

Relaxivities of paramagnetic liposomes: on the importance of the chain type and the length of the amphiphilic complex

Nuclear magnetic relaxation dispersion (NMRD) profiles of unilamellar DPPC liposomes incorporating Gd-DTPA-bisamides with alkyl chains of 12 to 18 C atoms in their external and internal layers were recorded in order to study the influence that the chain length and structure of Gd-bisamides incorporated in the liposomal membrane have on their proton relaxivity. The NMRD profiles recorded at 310 K show that the relaxivity reaches a minimum value when the carbon chain lengths of the phospholipid and of the Gd complex match and is at a maximum in the presence of a carbon-carbon double bond. For these DPPC paramagnetic liposomes, the longer the aliphatic chains of the complex, the larger will be its immobilization in the membrane. In addition, the presence of an unsaturated carbon-carbon bond in the alkyl chain of the Gd complex induces an increase of its mobility and of its water exchange rate with, as a result, a much greater efficiency as an MRI contrast agent.     

Drosophila retinal pigment cell death is regulated in a position-dependent manner by a cell memory gene

The stereotyped organization of the Drosophila compound eye depends on the elimination by apoptosis of about 25% of the inter-ommatidial pigment cell precursors (IOCs) during metamorphosis. This program of cell death is under antagonistic effects of the Notch and the EGFR pathways. In addition, uncharacterized positional cues may underlie death versus survival choices among IOCs. Our results provide new genetic evidences that cell death is regulated in a position- dependent manner in the eye. We show that mutations in Trithorax-like (Trl) and lola-like/batman specifically block IOC death during eye morphogenesis. These genes share characteristics of both Polycomb-Group and trithorax-Group genes, in that they are required for chromatin-mediated repression and activation of Hox genes. However, Trl function in triggering IOC death is independent from a function in repressing Hox gene expression during eye development. Analysis of mosaic ommatidiae containing Trl mutant cells revealed that Trl function for IOC death is required in cone cells. Strikingly, cell death suppression in Trl mutants depends on the position of IOCs. Our results further support a model whereby death of IOCs on the oblique sides of ommatidiae requires Trl-dependent reduction of a survival signal, or an increase of a death signal, emanating from cone cells. Trl does not have the same effect on horizontal IOCs whose survival seems to involve additional topological constraints.