Validation of the fluorescence polarization assay and comparison to other serological assays for the detection of serum antibodies to Brucella abortus in bison

A number of serological tests were compared for the detection of antibodies to Brucella abortus in bison (Bison bison). The performance of the fluorescence polarization assay (FPA) in both the preliminary evaluation and a subsequent blind validation indicated that this test was the most suitable for serological diagnosis of brucellosis in bison. The sensitivity and specificity in the preliminary evaluation were 92.1% and 99.4%, respectively. The sensitivity and specificity in a subsequent blind study were 96.3% and 97.6%, respectively. In a double blind study conducted on bison vaccinated with B. abortus strain 19, the data suggests that the FPA can differentiate bison infected with B. abortus from bison vaccinated with B. abortus strain 19. Both the indirect immunoassay (IELISA) and the competitive immunoassay (CELISA) performed nearly as well as the FPA. The buffered antigen plate agglutination test (BPAT) and the complement fixation test (CFT) did not perform as well as the FPA, CELISA or the IELISA in both studies. The FPA is a homogeneous assay eliminating the washing steps and reducing incubation to minutes rather than hours saving on time, equipment, materials, reagents and cost. These attributes, together, with its excellent sensitivity and specificity make the FPA an attractive test for the detection of serum antibodies to Brucella abortus in bison.     

Effect of moderate and high light on photosystem II function in Arabidopsis thaliana depleted in digalactosyl-diacylglycerol

The response of the heat-sensitive dgd1-2 and dgd1-3 Arabidopsis mutants depleted in the galactolipid DGDG to photoinhibition of chloroplasts photosystem II was studied to verify if there is a relationship between heat stress vulnerability due to depletion in DGDG and the susceptibility to photoinhibitory damage. Non-photochemical quenching (NPQ) is known to dissipate excessive absorbed light energy as heat to protect plants against photodamage. The main component of NPQ is dependent of the transthylakoid pH gradient and is modulated by zeaxanthin (Zx) synthesis. These processes together with chlorophyll fluorescence induction were used to characterize the response of the genotypes. The mutants were more sensitive to photoinhibition to a small extent but this was more severe for dgd1-3 especially at high light intensity. It was deduced that DGDG was not a main factor to influence photoinhibition but other lipid components could affect PSII sensitivity towards photoinhibition in relation to the physical properties of the thylakoid membrane. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.     

JML: testing hybridization from species trees

I introduce the software JML that tests for the presence of hybridization in multispecies sequence data sets by posterior predictive checking following Joly, McLenachan and Lockhart (2009, American Naturalist 174, e54). Although their method could potentially be applied on any data set, the lack of appropriate software made its application difficult. The software JML thus fills a need for an easy application of the method but also includes improvements such as the possibility to incorporate uncertainty in the species tree topology. The JML software uses a posterior distribution of species trees, population sizes and branch lengths to simulate replicate sequence data sets using the coalescent with no migration. A test quantity, defined as the minimum pairwise sequence distance between sequences of two species, is then evaluated on the simulated data sets and compared to the one estimated from the original data. Because the test quantity is a good predictor of hybridization events, departure from the bifurcating species tree model could be interpreted as evidence of hybridization. Software performance in terms of computing time is evaluated for several parameters. I also show an application example of the software for detecting hybridization among native diploid North American roses.     

Genetic engineering of attenuated malaria parasites for vaccination

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Highlights? Genetically attenuated parasites (GAPs) as potential vaccines against malaria. ? Attenuated Plasmodium sporozoites confer sustained sterile immunity against malaria. ? Rodent malaria models are an important in vivo platform to delineate GAP safety and potency. ? Late liver-arresting GAPs elicit superior protective immunity than early arresting parasites. ? P. falciparum GAP vaccine candidates need ultimately to be validated in clinical studies.     

Spread of social information and dynamics of social transmission within Drosophila groups

Understanding how behavioral diversity arises and is maintained is central to evolutionary biology. Genetically based inheritance has been a predominant research focus of the last century; however, nongenetic inheritance, such as social transmission, has become a topic of increasing interest [1]. How social information impacts behavior depends on the balance between information gathered directly through personal experience versus that gleaned through social interactions and on the diffusion of this information within groups [2, 3]. We investigate how female Drosophila melanogaster use social information under seminatural conditions and whether this information can spread and be maintained within a group, a prerequisite for establishing behavioral transmission [4]. We show that oviposition site choice is heavily influenced by previous social interactions. Naive observer flies develop a preference for the same egg-laying medium as experienced demonstrator flies conditioned to avoid one of two equally rewarding media. Surprisingly, oviposition site preference was socially transmitted from demonstrators to observers even when they interacted in a cage with only unflavored, pure agar medium, and even when the observer flies had previous personal experience with both rewarding media. Our findings shed light on the diffusion process of social information within groups, on its maintenance, and ultimately, on the roots of behavioral local adaptation.     

Morph switching in a dimorphic population of <Emphasis Type="Italic">Triturus alpestris</Emphasis> (Amphibia,Caudata)

The usual life cycle of Alpine newts comprises an aquatic larval stage and a terrestrial juvenile and adult stage. However, some populations differ from this pattern in exhibiting facultative paedomorphosis where some individuals reach sexual maturity while retaining larval traits such as gills and gill slits. While paedomorphic newts can, in some circumstances, initiate metamorphosis, once a newt has commenced metamorphosis, the state is irreversible. Because the frequency of this switching from one morph to the other has never been quantified in the wild, we attempted to estimate switching rate and survival by carrying out a 3-year monitoring survey of a population inhabiting an alpine lake. While morph switching did occur in this population, it involved a relatively low proportion of the paedomorphs (approx. 12%), suggesting that metamorphosis is not favoured in the study population. The hypothesis of paedomorphic advantage was not supported since neither survival nor body condition differed between morphs. The ontogenetic pathway of wild Alpine newts is thus characterised by two forks in the developmental pathway. The first occurs during the larval stage (metamorphosis vs. paedomorphosis), and the second occurs in paedomorphic adults (switching for metamorphosis vs. continuation of the paedomorphic lifestyle). Such a two-level decision process may allow individuals to cope with environmental uncertainty.     

The endocrine regulation of milk lipid synthesis and secretion in tammar wallaby (Macropus eugenii)

Lipids in tammar milk are predominantly triacylglycerols, and the fatty acid composition varies during the lactation cycle. Little is known about the regulation of their synthesis. This study investigates the endocrine regulation of lipid synthesis in mammary explants from pregnant tammars. Treatment of mammary explants with insulin resulted in a high level of lipid synthesis, but the lipids accumulated in the cytosol. Culture with prolactin resulted in a small increase in lipid synthesis, but electron microscopy showed lipid globules were synthesized in the mammary epithelial cells and secreted into the lumen. Culture with both insulin and prolactin demonstrated elevated levels of synthesis and secretion of lipid. Analysis of the type of fatty acids synthesized in these mammary explants showed that the initiation of synthesis of C_16:0, which also occurs in the first week of lactation, could be reproduced in the pregnant explants cultured with prolactin alone. However, treatment of mammary explants with hydrocortisone did not show a significant effect on lipid synthesis, secretion or the fatty acid synthesized. These results provide new information identifying the role of insulin and prolactin in regulating milk lipid synthesis and secretion in the tammar.