Structural analysis of four and half LIM protein-2 in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a cardiac disease characterized by dilated ventricle and systolic dysfunction. Most of the DCM patients are sporadic cases, but a certain population of DCM patients can be familial cases caused by mutations in genes for sarcomere/Z-disc components including titin/connectin. However, disease-causing mutations could be identified only in a part of the familial DCM patients, suggesting that there should be other disease causing genes for DCM. To explore a novel disease gene for DCM, we searched for mutations in FHL2, encoding for four and half LIM protein 2 (FHL2) in DCM patients, because FHL2 is known to associate with titin/connectin. A missense mutation, Gly48Ser, was identified in a patient with familial DCM. Functional analysis demonstrated that the FHL2 mutation affected the binding to titin/connectin. Because FHL2 protein is known to tether metabolic enzymes to titin/connectin, these observations suggest that the Gly48Ser mutation may be involved in the pathogenesis of DCM via impaired recruitment of metabolic enzymes to the sarcomere.     

Towards the adaptation of grapevine varieties to climate change: QTLs and candidate genes for developmental stages

The genetic determinism of developmental stages in grapevine was studied in the progeny of a cross between grapevine cultivars Riesling and Gewurztraminer by combining ecophysiological modelling, genetic analysis and data mining of the grapevine whole genome sequence. The dates of three phenological stages, budbreak, flowering and veraison, were recorded during four successive years for 120 genotypes in the vineyard. The phenotypic data analysed were the duration of three periods expressed in thermal time (degree-days): 15 February to budbreak (Bud), budbreak to flowering (Flo) and flowering to veraison (Ver). Parental and consensus genetic maps were built using 153 microsatellite markers on 188 individuals. Six independent quantitative trait loci (QTLs) were detected for the three phases. They were located on chromosomes 4 and 19 for Bud, chromosomes 7 and 14 for Flo and chromosomes 16 and 18 for Ver. Interactions were detected between loci and also between alleles at the same locus. Using the available grapevine whole-genome sequences, candidate genes underlying the QTLs were identified. VvFT, on chromosome 7, and a CONSTANS-like gene, on chromosome 14, were found to colocalise with the QTLs for flowering time. Genes related to the abscisic acid response and to sugar metabolism were detected within the confidence intervals of QTLs for veraison time. Their possible roles in the developmental process are discussed. These results raise new hypotheses for a better understanding of the physiological processes governing grapevine phenology and provide a framework for breeding new varieties adapted to the future predicted climatic conditions.     

Nutritional role of two algal symbionts in the temperate sea anemone Anthopleura elegantissima brandt

The intertidal sea anemone Anthopleura elegantissima in the Pacific Northwest may host a single type of algal symbiont or two different algal symbionts simultaneously: zooxanthellae (Symbiodinium muscatinei) and zoochlorellae (green algae; Trebouxiophyceae, Chlorophyta). A seasonal comparison of zooxanthellate and zoochlorellate anemones showed stable symbiont population densities in summer and winter, with densities of zoochlorellae about 4 times those of zooxanthellae. Photosynthesis-irradiance curves of freshly isolated symbionts show that the productivity (P(max) cell) of freshly isolated zooxanthellae was about 2.5 times that of zoochlorellae during July; comparable rates were obtained in other months. Models of algal carbon flux show that zoochlorellae may supply the host with more photosynthetic carbon per unit anemone biomass than zooxanthellae supply. Zooxanthellate anemone tissue was 2 per thousand ((13)C) and 5 per thousand ((15)N) enriched and zoochlorellate anemone tissue was 6 per thousand ((13)C) and 8 per thousand ((15)N) enriched over their respective symbionts, suggesting that zoochlorellate anemones receive less nutrition from their symbionts than do zooxanthellate individuals. The disparity between predicted contributions from the algal carbon budgets and the stable isotopic composition suggests that short-term measures of algal contributions may not reflect actual nutritional inputs to the host. Isotopic data support the hypothesis of substantial reliance on external food sources. This additional nutrition may allow both algae to persist in this temperate intertidal anemone in spite of differences in seasonal photosynthetic carbon contributions.     

First characterisation of the active oligomer form of sulfur oxygenase reductase from the bacterium Aquifex aeolicus

Sulfur oxygenase reductase (SOR) enzyme is responsible for the initial oxidation step of elemental sulfur in archaea. Curiously, Aquifex aeolicus, a hyperthermophilic, chemolithoautotrophic and microaerophilic bacterium, has the SOR-encoding gene in its genome. We showed, for the first time the presence of the SOR enzyme in A. aeolicus, its gene was cloned and recombinantly expressed in Escherichia coli and the protein was purified and characterised. It is a 16 homo-oligomer of approximately 600 kDa that contains iron atoms indispensable for the enzyme activity. The optimal temperature of SOR activity is 80°C and it is inactive at 20°C. Studies of the factors involved in getting the fully active molecule at high temperature show clearly that (1) incubation at high temperature induces more homogeneous form of the enzyme, (2) conformational changes observed at high temperature are required to get the fully active molecule and (3) acquisition of an active conformation induced by the temperature seems to be more important than the subunit number. Differences between A. aeolicus SOR and the archaea SORs are described.     

Genetic diversity of native bradyrhizobia isolated from soybeans (Glycine max L.) in different agricultural-ecological-climatic regions of India

Fifty isolates from root nodules of soybean plants sampled in five agricultural-ecological-climatic regions of India were analyzed by PCR-restriction fragment length polymorphism analysis of the 16S rRNA gene, the intergenic spacer region between the 16S and 23S rRNA genes (IGS), and the nifH and nodC genes. Eight haplotypes assigned to the Bradyrhizobium genus were identified, and the genetic diversity was conserved across regions. Sequence analyses of the IGS and the dnaK, glnII, recA, and nifH genes revealed three groups. One of them (26% of isolates) was assigned to Bradyrhizobium liaoningense. A second group (36% of isolates) was identified as B. yuanmingense but likely forms a new biovar able to nodulate soybean plants. The third lineage (38% of isolates) was different from all described Bradyrhizobium species but showed the same symbiotic genotype as B. liaoningense and B. japonicum bv. glycinearum.     

Plant phenology and genetic variability in root and nodule development strongly influence genetic structuring of Rhizobium leguminosarum biovar viciae populations nodulating pea

The symbiotic relationships between legumes and their nitrogen (N(2))-fixing bacterial partners (rhizobia) vary in effectiveness to promote plant growth according to both bacterial and legume genotype. To assess the selective effect of host plant on its microsymbionts, the influence of the pea (Pisum sativum) genotype on the relative nodulation success of Rhizobium leguminosarum biovar viciae (Rlv) genotypes from the soil populations during plant development has been investigated. Five pea lines were chosen for their genetic variability in root and nodule development. Genetic structure and diversity of Rlv populations sampled from nodules were estimated by molecular typing with a marker of the genomic background (rDNA intergenic spacer) and a nodulation gene marker (nodD region). Differences were found among Rlv populations related to pea genetic background but also to modification of plant development caused by single gene mutation. The growth stage of the host plant also influenced structuring of populations. A particular nodulation genotype formed the majority of nodules during the reproductive stage. Overall, modification in root and nodule development appears to strongly influence the capacity of particular rhizobial genotypes to form nodules.     

Virulent synergistic effect between Enterococcus faecalis and Escherichia coli assayed by using the Caenorhabditis elegans model

Background

The role of enterococci in the pathogenesis of polymicrobial infections is still debated. The purpose of this study was to evaluate the effect of virulent enterococci in the presence or absence of Escherichia coli strains in the in vivo Caenorhabditis elegans model.

Principal Findings

This study demonstrated that there was a synergistic effect on virulence when an association of enterococci and E. coli (LT50 = 1.6 days±0.1 according to the tested strains and death of nematodes in 4 days±0.5) was tested in comparison with enterococci alone (LT50 = 4.6 days±0.1 and death in 10.4 days±0.6) or E. coli alone (LT50 = 2.1±0.9 and deaths 6.6±0.6) (p<0.001). In addition, there was a relation between the virulence of E. faecalis strains alone and the virulence potential of the association with E. coli strains. Finally, in the presence of avirulent E. coli strains, enterococci have no effect (LT50 = 4.3±0.5 and deaths in 10.8±0.8), independently of the level of their own virulence, demonstrating that the ‘enterococci effect’ only occurred in the presence of virulent E. coli strains.

Conclusion

This study allows a better understanding of a bacterial cooperation. Moreover, it could help to optimize the antibiotic regimen during polymicrobial infections.     

3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL): cloning and characterization of a mouse liver HL cDNA and subchromosomal mapping of the human and mouse HL genes

3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL) is a homodimeric mitochondrial matrix enzyme that catalyzes the last step of ketogenesis. Using a human HL cDNA as a probe, we isolated a 1.4-kb mouse HL cDNA (HLM) from a mouse liver library and extended the sequence in the 5 direction, using RACE PCR to include the complete coding sequence. The nucleotide sequence of the mouse HL coding region is 85.7% identical to human HL, and 52.6% to Ps. mevalonii HL. Peptide identities of 87.4% and 54.3% respectively were observed. Southern analysis of 29 strains of laboratory mice and of Mus spretus revealed a total of about 25 kb of hybridizing fragments and three polymorphic fragments in both EcoRI and HindIII digestions. The mouse HL locus (Hmgcl) was localized on Chromosome (Chr) 4: Pmv-19-12.6±3.6 cM-Hmgcl-7.3±2.3 cM-Xmv-8-1.5±1.0 cM-Gpd1. The human HL locus (HMGCL) was mapped to distal Chr 1p by analysis of a human-hamster hybrid cell panel and by in situ hybridization.