Contrasted Microcolinearity and Gene Evolution Within a Homoeologous Region of Wheat and Barley Species

We study here the evolution of genes located in the same physical locus using the recently sequenced Ha locus in seven wheat genomes in diploid, tetraploid, and hexaploid species and compared them with barley and rice orthologous regions. We investigated both the conservation of microcolinearity and the molecular evolution of genes, including coding and noncoding sequences. Microcolinearity is restricted to two groups of genes (Unknown gene-2, VAMP, BGGP, Gsp-1, and Unknown gene-8 surrounded by several copies of ATPase), almost conserved in rice and barley, but in a different relative position. Highly conserved genes between wheat and rice run along with genes harboring different copy numbers and highly variable sequences between close wheat genomes. The coding sequence evolution appeared to be submitted to heterogeneous selective pressure and intronic sequences analysis revealed that the molecular clock hypothesis is violated in most cases.     

The non-linear response of a muscle in transverse compression: assessment of geometry influence using a finite element model

Most recent finite element models that represent muscles are generic or subject-specific models that use complex, constitutive laws. Identification of the parameters of such complex, constitutive laws could be an important limit for subject-specific approaches. The aim of this study was to assess the possibility of modelling muscle behaviour in compression with a parametric model and a simple, constitutive law. A quasi-static compression test was performed on the muscles of dogs. A parametric finite element model was designed using a linear, elastic, constitutive law. A multi-variate analysis was performed to assess the effects of geometry on muscle response. An inverse method was used to define Young's modulus. The non-linear response of the muscles was obtained using a subject-specific geometry and a linear elastic law. Thus, a simple muscle model can be used to have a bio-faithful, biomechanical response.     

Extracellular signal-regulated kinase 1 interacts with and phosphorylates CdGAP at an important regulatory site

Rho GTPases regulate multiple cellular processes affecting both cell proliferation and cytoskeletal dynamics. Their cycling between inactive GDP- and active GTP-bound states is tightly regulated by guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We have previously identified CdGAP (for Cdc42 GTPase-activating protein) as a specific GAP for Rac1 and Cdc42. CdGAP consists of an N-terminal RhoGAP domain and a C-terminal proline-rich region. In addition, CdGAP is a member of the impressively large number of mammalian RhoGAP proteins that is well conserved among both vertebrates and invertebrates. In mice, we find two predominant isoforms of CdGAP differentially expressed in specific tissues. We report here that CdGAP is highly phosphorylated in vivo on serine and threonine residues. We find that CdGAP is phosphorylated downstream of the MEK-extracellular signal-regulated kinase (ERK) pathway in response to serum or platelet-derived growth factor stimulation. Furthermore, CdGAP interacts with and is phosphorylated by ERK-1 and RSK-1 in vitro. A putative DEF (docking for ERK FXFP) domain located in the proline-rich region of CdGAP is required for efficient binding and phosphorylation by ERK1/2. We identify Thr776 as an in vivo target site of ERK1/2 and as an important regulatory site of CdGAP activity. Together, these data suggest that CdGAP is a novel substrate of ERK1/2 and mediates cross talk between the Ras/mitogen-activated protein kinase pathway and regulation of Rac1 activity.     

Agrobacterium rhizogenes-mediated transformation of Prunus as an alternative for gene functional analysis in hairy-roots and composite plants

Resistant rootstocks offer an alternative to pesticides for the control of soil pests. In Prunus spp., resistance loci to root-knot nematodes (RKN) have been mapped and a transformation method is needed to validate candidate genes. Our efforts have focused on the generation of transformed hairy-roots and composite plants appropriate for nematode infection assays. An efficient and reliable method using the A4R strain of Agrobacterium rhizogenes for the transformation of Prunus roots with an Egfp reporter gene is given. The rooting efficiency, depending on the genotypes, was maximal for the interspecific hybrid 253 (Myrobalan plum?×?almond-peach), susceptible to RKN, that was retained for subsequent studies. From the agro-inoculated cuttings, 72% produced roots, mainly at the basal section of the stem. Transformed roots were screened by microscope detection of Egfp fluorescence and molecular analyses of the integration of the transgene. The absence of residual agrobacteria in the plants was checked by the non-amplification of the chromosomal gene chvH. Egfp was expressed visually in 76% of the rooted plants. Isolated hairy roots in Petri dishes and composite plants (transformed roots and non-transformed aerial part) in soil containers were inoculated with the RKN Meloidogyne incognita. In both cases, root transformation did not affect the ability of the nematodes to develop in the root tissues. Our results showed that isolated hairy-roots can be used to validate candidate genes and the conditions in which composite plants offer a complementary system for studying the function of root genes in physiological conditions of whole plants are discussed.     

The loss of metabolic control on alcohol drinking in heavy drinking alcohol-dependent subjects

Background

Most physiological studies interested in alcohol-dependence examined ethanol as a pharmacological agent rather than a nutrient. We conducted two studies, which assessed the metabolic and endocrine factors involved in the regulation of alcohol and nutrient intake in alcohol-dependent (AD) subjects. We also examined the potential role of a disruption in energy balance in alcohol-dependence.

Methods and Results

In Study-1, quantitative dietetic interviews of eating and drinking habits were conducted with 97 AD subjects. The population was split around a median alcohol intake value of 12.5 kcal/kg/day. The results showed that the “low alcohol” drinking AD subjects had high Body Mass Index (BMI) and Fat Mass (FM) and alcohol intake was compensated for by a decrease in non-alcoholic intakes. “High alcohol” drinking AD subjects, on the other hand, had low BMI and FM and the total caloric intakes were largely above norms. In Study-2, 24 AD inpatients were submitted to dietetic interviews, calorimetry and blood samplings for the measurement of biomarkers of the regulation of metabolism and satiety, on day 2, 5 and 16 of abstinence. These patients were compared with 20 controls matched for age and gender. We observed in AD patients an increase in cortisol, leptin and PYY plasma levels and a decrease in ghrelin, which might explain the observed decrease in non-alcoholic intakes. However, alcoholic and non-alcoholic intakes correlated positively with basal metabolism and negatively with leptin and leptin/BMI.

Conclusion

For individuals consuming below12.5 kcal/kg/day of alcohol, alcohol intake is compensated for by a decrease in non-alcoholic nutrient intakes, probably due to changes in metabolic and satiety factors. For individuals consuming above 12.5 kcal/kg/day of alcohol, alcohol accelerates metabolism and decreases fat mass and leptin levels, and the total caloric intake largely exceeds norms. A dual model for regulation of energy intake in AD subjects is proposed.     

Caveolae Contribute to the Apoptosis Resistance Induced by the α1A-Adrenoceptor in Androgen-Independent Prostate Cancer Cells

Background

During androgen ablation prostate cancer cells'' growth and survival become independent of normal regulatory mechanisms. These androgen-independent cells acquire the remarkable ability to adapt to the surrounding microenvironment whose factors, such as neurotransmitters, influence their survival. Although findings are becoming evident about the expression of α_1A-adrenoceptors in prostate cancer epithelial cells, their exact functional role in androgen-independent cells has yet to be established. Previous work has demonstrated that membrane lipid rafts associated with key signalling proteins mediate growth and survival signalling pathways in prostate cancer cells.

Methodology/Principal Findings

In order to analyze the membrane topology of the α_1A-adrenoceptor we explored its presence by a biochemical approach in purified detergent resistant membrane fractions of the androgen-independent prostate cancer cell line DU145. Electron microscopy observations demonstrated the colocalisation of the α_1A-adrenoceptor with caveolin-1, the major protein component of caveolae. In addition, we showed that agonist stimulation of the α_1A-adrenoceptor induced resistance to thapsigargin-induced apoptosis and that caveolin-1 was necessary for this process. Further, immunohistofluorescence revealed the relation between high levels of α_1A-adrenoceptor and caveolin-1 expression with advanced stage prostate cancer. We also show by immunoblotting that the TG-induced apoptosis resistance described in DU145 cells is mediated by extracellular signal-regulated kinases (ERK).

Conclusions/Significance

In conclusion, we propose that α_1A-adrenoceptor stimulation in androgen-independent prostate cancer cells via caveolae constitutes one of the mechanisms contributing to their protection from TG-induced apoptosis.     

New Insights in the Life Cycle and Epidemics of Phytophthora porri on Leek

White tip, caused by Phytophthora porri, is a devastating disease in the autumn and winter production of leek (Allium porrum) in Europe. This study investigated the disease cycle of P. porri in laboratory and field conditions. Oospores readily germinated in the presence of non‐sterile soil extract at any temperature between 4 and 22°C, with the formation of sporangia which released zoospores. The zoospores survived at least 7 weeks in water at a temperature range of 0 till 24°C. Microscopic examinations revealed that zoospores encysted and germinated on the leek leaf surface and hyphae entered the leaf directly through stomata or by penetrating via appressoria. Oospores were formed in the leaves within 6 days, while sporangia were not produced. By monitoring disease progress in fields with a different cropping history of leek, it could be deduced that P. porri survives in soil for up to 4 years. Disease progress during three consecutive years was correlated with average daily rainfall in the infection period. Disease incidence on leek was reduced when rain splash was excluded by growing the plants in an open hoop greenhouse. Based on these findings, we propose a disease cycle for P. porri in which oospores germinate in puddles, and zoospores reach the leaves by rain splash and survive in water in the leaf axils, from where they infect the plant by direct penetration or via stomata. When conditions become unfavourable, oospores are produced in the leaves which again reach the soil when leaves decay. Secondary spread of the disease by sporangia does not seem to be important.