Mutations affecting translational fidelity in the eucaryote Podospora anserina: Characterization of two ribosomal restrictive mutations

Summary Fifty-nine mutations that restrict suppressor efficiency were selected in the fungus Podospra anserina using four different screening methods. Previous genetic analysis has shown that these antisuppressors lie in six loci and that they could be similar to ribosomal restrictive mutations known in Escherichia coli. The present study deals with the response of two of them, AS1-1 and AS6-1, to paromomycin and low temperature both in vivo and in vitro. The data demonstrate that ribosomes of the mutant and double-mutant strains are equally resistant to the ambiguity effect of paromomycin. These data are the first demonstration of mutations that increase translational fidelity in a eucaryotic organism.     

La variabilité cytologique dans la descendance des femelles de Luffia ferchaultella steph. (Lepidoptera psychidae)

Summary The procedure which leads to the restoration of the diploid chromosomal number in the egg of the parthenogenetic Luffia ferchaultella is similar in all the eggs laid by one female. But it may vary in the eggs of closely related females (mother and daughters or sisters). Therefore it is not a characteristic of the parthenogenetic strain.

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Au Professeur Bauer, en témoignage d'admiration.

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Travail subventionné par le Fonds National Suisse de la Recherche Scientifique.     

Inter-annual variability in the environmental performance of viticulture technical management routes—a case study in the Middle Loire Valley (France)

Purpose

Improving the environmental performances of viticulture practices is particularly complicated during unfavorable climatic conditions because of the need for fungal and other pest pressure and the variability of phytosanitary control methods available for winegrowers. However, winegrowers wish to improve the environmental performances of their practices regardless of climatic conditions. The objective of the study was to quantify the variability in environmental impacts due to climatic variations, and changes in viticulture practices induced by climatic variability.

Methods

Life cycle assessment was used to evaluate the environmental impacts of viticulture technical management routes (TMR) implemented on five plots in the Loire Valley for the Chenin Blanc grape variety. These TMRs are representative of the range of practices used in the region, including intensive conventional practices to moderate organic practices. The study covered two different years of production (2011 and 2013) under contrasting climatic conditions. The first year (2011) was hot and dry, which are favorable conditions for viticulture, while the second year (2013) was cold and humid, which are unfavorable conditions.

Results and discussion

During the unfavorable year, the number of phytosanitary treatments and soil maintenance interventions increased for most of the studied TMRs. This meant that the inter-annual variability in environmental impact was significant, depending on the type of TMR, with differences in impacts ranging from 19% to more than 40% between 2011 and 2013. Managing environmental impacts was found to be more difficult for the organic systems when climatic conditions are unfavorable (in 2013). The non-organic TMRs showed less variation in environmental impacts than the organic TMRs between the 2 years studied.

Conclusions

This study shows the importance of taking into account inter-annual variability in environmental assessments of viticulture systems. Indeed, winegrowers do not respond the same way to climate variability mainly with regard to plant protection and soil maintenance. Viticulture is very sensitive to inter-annual climate variations due to the parasitic pressure variability. The different production systems do not give to winegrowers the same possibilities for adapting practices to limit their impact on the environment.

     

Aeschynomene evenia, a model plant for studying the molecular genetics of the nod-independent rhizobium-legume symbiosis

Research on the nitrogen-fixing symbiosis has been focused, thus far, on two model legumes, Medicago truncatula and Lotus japonicus, which use a sophisticated infection process involving infection thread formation. However, in 25% of the legumes, the bacterial entry occurs more simply in an intercellular fashion. Among them, some Aeschynomene spp. are nodulated by photosynthetic Bradyrhizobium spp. that do not produce Nod factors. This interaction is believed to represent a living testimony of the ancestral state of the rhizobium-legume symbiosis. To decipher the mechanisms of this Nod-independent process, we propose Aeschynomene evenia as a model legume because it presents all the characteristics required for genetic and molecular analysis. It is a short-perennial and autogamous species, with a diploid and relatively small genome (2n=20; 460 Mb/1C). A. evenia 'IRFL6945' is nodulated by the well-characterized photosynthetic Bradyrhizobium sp. strain ORS278 and is efficiently transformed by Agrobacterium rhizogenes. Aeschynomene evenia is genetically homozygous but polymorphic accessions were found. A manual hybridization procedure has been set up, allowing directed crosses. Therefore, it should be relatively straightforward to unravel the molecular determinants of the Nod-independent process in A. evenia. This should shed new light on the evolution of rhizobium-legume symbiosis and could have important agronomic implications.     

Ileal oxalate absorption and urinary oxalate excretion are enhanced in Slc26a6 null mice

Intestinal oxalate transport, mediated by anion exchange proteins, is important to oxalate homeostasis and consequently to calcium oxalate stone diseases. To assess the contribution of the putative anion transporter (PAT)1 (Slc26a6) to transepithelial oxalate transport, we compared the unidirectional and net fluxes of oxalate across isolated, short-circuited segments of the distal ileum of wild-type (WT) mice and Slc26a6 null mice [knockout (KO)]. Additionally, urinary oxalate excretion was measured in both groups. In WT mouse ileum, there was a small net secretion of oxalate (J(net)(Ox) = -5.0 +/-5.0 pmol.cm(-2).h(-1)), whereas in KO mice J(net)(Ox) was significantly absorptive (75 +/- 10 pmol.cm(-2)h.h(-1)), which was the result of a smaller serosal-to-mucosal oxalate flux (J(sm)(Ox)) and a larger mucosal-to-serosal oxalate flux (J(ms)(Ox)). Mucosal DIDS (200 microM) reduced J(sm)(Ox) in WT mice, leading to reversal of the direction of net oxalate transport from secretion to absorption (J(net)(Ox) = 15.0 +/- 5.0 pmol.cm(-2).h(-1)) , but DIDS had no significant effect on KO ileum. In WT mice in the absence of mucosal Cl(-), there were small increases in J(ms)(Ox) and decreases in J(sm)(Ox) that led to a small net oxalate absorption. In KO mice, J(net)(Ox) was 1.5-fold greater in the absence of mucosal Cl(-), due solely to an increase in J(ms)(Ox). Urinary oxalate excretion was about fourfold greater in KO mice compared with WT littermates. We conclude that PAT1 is DIDS sensitive and mediates a significant fraction of oxalate efflux across the apical membrane in exchange for Cl(-); as such, PAT1 represents a major apical membrane pathway mediating J(sm)(Ox).     

High-level production and purification of a fully active recombinant dextransucrase from Leuconostoc mesenteroides NRRL B-512F

Recombinant expression of the dextransucrase dsrS gene by Escherichia coli was optimized to produce 5850 U L(-1) (culture) of DSR-S, corresponding to a 30-fold increase compared with previous studies. Rational deletions of the signal peptide, the beginning of the variable region and the last four repeats of the C-terminal end caused no loss of activity. This new variant successfully purified was remarkably stable. With a k(cat) of 584 s(-1), it is the most efficient recombinant glucansucrase described to date. The synthesized polymer possesses more than 95% of alpha-1,6 links, like the dextran produced by the native enzyme, and innovative gel properties were obtained.     

Lessons from pandemic H1N1 2009 to improve prevention, detection, and response to influenza pandemics from a One Health perspective

In April 2009, a novel influenza A subtype H1N1 triple reassortant virus (novel H1N1 2009), composed of genes from swine, avian, and human influenza A viruses, emerged in humans in the United States and Mexico and spread person-to-person around the world to become the first influenza pandemic of the 21st century. The virus is believed to have emerged from a reassortment event involving a swine virus some time in the past 10 to 20 years, but pigs, pork, and pork products have not been involved with infection or spread of the virus to or among people. Because countries quickly implemented recently developed pandemic influenza plans, the disease was detected and reported and public health authorities instituted control measures in a timely fashion. But the news media's unfortunate and inappropriate naming of the disease as the "swine flu" led to a drop in the demand for pork and several countries banned pork imports from affected countries, resulting in serious negative economic impacts on the pork industry. With the continual circulation and interspecies transmission of human, swine, and avian influenza viruses in countries around the world, there are calls for strengthening influenza surveillance in pigs, birds, and other animals to aid in monitoring and assessing the risk of future pandemic virus emergence involving different species. We identify and discuss several lessons to be learned from pandemic H1N1 2009 from a One Health perspective, as stronger collaboration among human, animal, and environmental health sectors is necessary to more effectively prevent or detect and respond to influenza pandemics and thus improve human, animal, and environmental health and well-being.     

Obtaining valid laboratory data in clinical trials conducted in resource diverse settings: lessons learned from a microbicide phase III clinical trial

Background

Over the last decade several phase III microbicides trials have been conducted in developing countries. However, laboratories in resource constrained settings do not always have the experience, infrastructure, and the capacity to deliver laboratory data meeting the high standards of clinical trials. This paper describes the design and outcomes of a laboratory quality assurance program which was implemented during a phase III clinical trial evaluating the efficacy of the candidate microbicide Cellulose Sulfate 6% (CS) [1].

Methodology

In order to assess the effectiveness of CS for HIV and STI prevention, a phase III clinical trial was conducted in 5 sites: 3 in Africa and 2 in India. The trial sponsor identified an International Central Reference Laboratory (ICRL), responsible for the design and management of a quality assurance program, which would guarantee the reliability of laboratory data. The ICRL provided advice on the tests, assessed local laboratories, organized trainings, conducted supervision visits, performed re-tests, and prepared control panels. Local laboratories were provided with control panels for HIV rapid tests and Chlamydia trachomatis/Neisseria gonorrhoeae (CT/NG) amplification technique. Aliquots from respective control panels were tested by local laboratories and were compared with results obtained at the ICRL.

Results

Overall, good results were observed. However, discordances between the ICRL and site laboratories were identified for HIV and CT/NG results. One particular site experienced difficulties with HIV rapid testing shortly after study initiation. At all sites, DNA contamination was identified as a cause of invalid CT/NG results. Both problems were timely detected and solved. Through immediate feedback, guidance and repeated training of laboratory staff, additional inaccuracies were prevented.

Conclusions

Quality control guidelines when applied in field laboratories ensured the reliability and validity of final study data. It is essential that sponsors provide adequate resources for implementation of such comprehensive technical assessment and monitoring systems.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00153777","term_id":"NCT00153777"}}NCT00153777 and Current Controlled Trials ISRCTN95638385