Prevalence and Diversity of Viruses in the Entomopathogenic Fungus Beauveria bassiana

Viruses have been discovered in numerous fungal species, but unlike most known animal or plant viruses, they are rarely associated with deleterious effects on their hosts. The knowledge about viruses among entomopathogenic fungi is very limited, although their existence is suspected because of the presence of virus-like double-stranded RNA (dsRNA) in isolates of several species. Beauveria bassiana is one of the most-studied species of entomopathogenic fungi; it has a cosmopolitan distribution and is used as a biological control agent against invertebrates in agriculture. We analyzed a collection of 73 isolates obtained at different locations and from different habitats in Spain and Portugal, searching for dsRNA elements indicative of viral infections. The results revealed that the prevalence of viral infections is high; 54.8% of the isolates contained dsRNA elements with viral characteristics. The dsRNA electropherotypes of infected isolates indicated that virus diversity was high in the collection analyzed and that mixed virus infections occurred in fungal isolates. However, a hybridization experiment indicated that dsRNA bands that are similar in size do not always have similar sequences. Particular virus species or dsRNA profiles were not associated with locations or types of habitats, probably because of the ubiquity and efficient dispersion of this fungus as an airborne species. The sequence of one of the most common dsRNA elements corresponded to the 5.2-kbp genome of a previously undescribed member of the Totiviridae family, termed B. bassiana RNA virus 1 (BbRV1).     

Influence of two different green algal diets on specific dynamic action and incorporation of carbon into biochemical fractions in the copepod Acartia tonsa

Previous studies have shown that the two green algae Tetraselmissp. (Prasinophyceae) and Dunaliella tertiolecta (Chlorophyceae)induce high and low egg production rates in Acartia tonsa. Theprimary goal of the present study was to investigate if thisis attributable to differences in the specific dynamic action(SDA) of the two diets. Secondly, we wanted to investigate ifany qualitative differences in the incorporation of nutritionalconstituents from the two diets are influencing SDA. The functionalresponse of ingestion was very different with the two diets.Ingestion of T. impellucida was relatively high even at lowfood concentrations with a maximum of 19 µg C ind^-1 day^-1.The functional response was more clearly sigmoidal on D. tertiolectawith a maximum of 7.3 µg C ind^-1 day^-1. The higher ingestionrate of T. impellucida also induced higher respiration rates.Maximum respiration rates were 3.0 nl O₂ ind^-1 min^-1 on T. impellucidaand 1.5 nl O₂ ind^-1 min^-1 onD. tertiolecta. This created significantlydifferent SDA coefficients: 0.19 on T. impellucida and 0.06on D. tertiolecta, which implies that the magnitude of SDA isstrongly influenced by the composition of the diet. The incorporationof carbon into lipids was significantly higher on D. tertiolecta.However, because of lack of longer chain fatty acids in D. tertiolectathe copepods did not benefit from this. Thus, the proportionof carbon allocated to egg lipids was much lower than when feedingon T. impellucida. Acartia tonsa incorporated relatively morecarbon into proteins when feeding on T. impellucida than onD. tertiolecta. Since protein synthesis is energetically verydemanding this is probably the reason for the higher SDA coefficientin those feeding on T. impellucida.     

MALDI-TOF mass spectrometry is a fast and reliable platform for identification and ecological studies of species from family Rhizobiaceae

Family Rhizobiaceae includes fast growing bacteria currently arranged into three genera, Rhizobium, Ensifer and Shinella, that contain pathogenic, symbiotic and saprophytic species. The identification of these species is not possible on the basis of physiological or biochemical traits and should be based on sequencing of several genes. Therefore alternative methods are necessary for rapid and reliable identification of members from family Rhizobiaceae. In this work we evaluated the suitability of Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for this purpose. Firstly, we evaluated the capability of this methodology to differentiate among species of family Rhizobiaceae including those closely related and then we extended the database of MALDI Biotyper 2.0 including the type strains of 56 species from genera Rhizobium, Ensifer and Shinella. Secondly, we evaluated the identification potential of this methodology by using several strains isolated from different sources previously identified on the basis of their rrs, recA and atpD gene sequences. The 100% of these strains were correctly identified showing that MALDI-TOF MS is an excellent tool for identification of fast growing rhizobia applicable to large populations of isolates in ecological and taxonomic studies.     

Importance of multi-dimensional analyses of resource partitioning in highly mobile species assemblages

Resource partitioning is an essential mechanism enabling species coexistence. The resources that are used by an animal are linked to its morphology and ecology. Therefore, similar species should use similar resources. The ecological niche of an individual summarizes all used resources and is therefore composed of several dimensions. Many methods are established to study different dimensions of an animal's niche. The aim of this study was to demonstrate that a combination of suitable methods is needed to study spatial and dietary resource partitioning of sympatric species in detail. We hypothesized that, while each individual method might identify differences between species, the combined results of several methods will lead to a more complete picture of spatial and dietary resource partitioning. As model organisms we chose the sympatric insectivorous bat species Myotis bechsteinii, M. nattereri, and P. auritus. We examined horizontal habitat use by telemetry, vertical habitat use by measuring δ¹³C, trophic position by measuring δ¹⁵N in wing membrane, and diet composition by molecular fecal analysis. Our results show that each method is able to provide information about spatial/dietary resource partitioning. However, considering further dimensions by combining several methods allows a more comprehensive assessment of dietary and spatial resource partitioning in bats.     

Characterization of phosphate solubilizing rhizobacteria associated with pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) isolated from two agricultural soils

Phosphorous (P) availability is a major concern in European agriculture where reserves are limited. In the case of pea (Pisum sativum L.), one of the most important legumes in the human diet, P has specific effects on nodulation and N₂ fixation. Therefore, when biofertilization schemes are considered for pea cropping, it is very important to include symbiotic dinitrogen-fixing bacteria as well as phosphate-solubilizing bacteria (PSB). In this study sixteen PSB were isolated from the rhizosphere of two pea cultivars in two French soils with different characteristics. They were phenotypically and genotypically diverse displaying 9 different Two Primers-Random Amplified Polymorphic DNA (TP-RAPD) patterns. The 16S rRNA gene analysis of representative strains showed that they belong to four highly divergent phylogenetic groups. Most of the PSB strains belonged to the genus Pseudomonas and were closely related to Pseudomonas baetica, P. lutea, P. azotoformans, P. jessenii and P. frederiksbergensis. Other strains from the genus Burkholderia were closely related to B. caledonica and those from the genus Rhizobium to R. grahamii. The single strain of genus Bacillus was close to Bacillus toyonensis. Some phylogenetic groups to which our PSB strains belong are widely distributed in plant rhizospheres in different countries and continents. This is particularly interesting in the case of strains from the phylogenetic group of P. fluorescens which includes PSB strains with high ability to solubilize phosphate indicating that they may be used as biofertilizers in many soils.     

Modulation of microtubule interprotofilament interactions by modified taxanes

Microtubules assembled with paclitaxel and docetaxel differ in their numbers of protofilaments, reflecting modification of the lateral association between αβ-tubulin molecules in the microtubule wall. These modifications of microtubule structure, through a not-yet-characterized mechanism, are most likely related to the changes in tubulin-tubulin interactions responsible for microtubule stabilization by these antitumor compounds. We have used a set of modified taxanes to study the structural mechanism of microtubule stabilization by these ligands. Using small-angle x-ray scattering, we have determined how modifications in the shape and size of the taxane substituents result in changes in the interprotofilament angles and in their number. The observed effects have been explained using NMR-aided docking and molecular dynamic simulations of taxane binding at the microtubule pore and luminal sites. Modeling results indicate that modification of the size of substituents at positions C7 and C10 of the taxane core influence the conformation of three key elements in microtubule lateral interactions (the M-loop, the S3 β-strand, and the H3 helix) that modulate the contacts between adjacent protofilaments. In addition, modifications of the substituents at position C2 slightly rearrange the ligand in the binding site, modifying the interaction of the C7 substituent with the M-loop.     

Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a Threatened Species Native to the Brazilian Cerrado

The threatened caesalpinioid legume Dimorphandra wilsonii, which is native to the Cerrado biome in Brazil, was examined for its nodulation and N₂-fixing ability, and was compared with another, less-threatened species, D. jorgei. Nodulation and potential N₂ fixation was shown on seedlings that had been inoculated singly with five bradyrhizobial isolates from mature D. wilsonii nodules. The infection of D. wilsonii by two of these strains (Dw10.1, Dw12.5) was followed in detail using light and transmission electron microscopy, and was compared with that of D. jorgei by Bradyrhizobium strain SEMIA6099. The roots of D. wilsonii were infected via small transient root hairs at 42 d after inoculation (dai), and nodules were sufficiently mature at 63 dai to express nitrogenase protein. Similar infection and nodule developmental processes were observed in D. jorgei. The bacteroids in mature Dimorphandra nodules were enclosed in plant cell wall material containing a homogalacturonan (pectic) epitope that was recognized by the monoclonal antibody JIM5. Analysis of sequences of their rrs (16S rRNA) genes and their ITS regions showed that the five D. wilsonii strains, although related to SEMIA6099, may constitute five undescribed species of genus Bradyrhizobium, whilst their nodD and nifH gene sequences showed that they formed clearly separated branches from other rhizobial strains. This is the first study to describe in full the N₂-fixing symbiotic interaction between defined rhizobial strains and legumes in the sub-family Caesalpinioideae. This information will hopefully assist in the conservation of the threatened species D. wilsonii.     

Multiple sclerosis risk variant HLA-DRB1*1501 associates with high expression of DRB1 gene in different human populations

The human leukocyte antigen (HLA) DRB1*1501 has been consistently associated with multiple sclerosis (MS) in nearly all populations tested. This points to a specific antigen presentation as the pathogenic mechanism though this does not fully explain the disease association. The identification of expression quantitative trait loci (eQTL) for genes in the HLA locus poses the question of the role of gene expression in MS susceptibility. We analyzed the eQTLs in the HLA region with respect to MS-associated HLA-variants obtained from genome-wide association studies (GWAS). We found that the Tag of DRB1*1501, rs3135388 A allele, correlated with high expression of DRB1, DRB5 and DQB1 genes in a Caucasian population. In quantitative terms, the MS-risk AA genotype carriers of rs3135388 were associated with 15.7-, 5.2- and 8.3-fold higher expression of DQB1, DRB5 and DRB1, respectively, than the non-risk GG carriers. The haplotype analysis of expression-associated variants in a Spanish MS cohort revealed that high expression of DRB1 and DQB1 alone did not contribute to the disease. However, in Caucasian, Asian and African American populations, the DRB1*1501 allele was always highly expressed. In other immune related diseases such as type 1 diabetes, inflammatory bowel disease, ulcerative colitis, asthma and IgA deficiency, the best GWAS-associated HLA SNPs were also eQTLs for different HLA Class II genes. Our data suggest that the DR/DQ expression levels, together with specific structural properties of alleles, seem to be the causal effect in MS and in other immunopathologies rather than specific antigen presentation alone.