Light effects on pyrethrum shoot cultures

Light consistently increased the pyrethrin content of pyrethrum shoot organ cultures. Under the experimental conditions used, the pyrethrin increase was not dependent upon a constant light supply.     

Effects of inbreeding and environmental stress on fitness – using Drosophila buzzatii as a model organism

Wild endangered populations can suffer fromadverse effects on fitness due to inbreedingand environmental stress. Often, both geneticand environmental stress factors may be presentin populations at the same time. Thereforeknowledge on the potential interactions betweenthese factors is important for the conservationof wild populations. When measuring fitness(e.g. survival and reproductive potential) ofindividuals in the laboratory, and in nature,inbreeding by environment interactions are nowbeing reported more often. The increased focuson environmental dependency of inbreedingdepression will therefore enable conservationbiologists to include this knowledge in themanagement of endangered populations in thewild. In this study, the effects ofenvironmental stress and inbreeding on fitnessare estimated in a laboratory population ofDrosophila buzzatii. Random- or full-sibmating were used to generate independentreplicate lines of four different inbreedinglevels (F = 0, F = 0.25, F = 0.50, F = 0.672)in four different environments. Theenvironments were thermal and dimethoate stressseparately and in combination, as well as anon-stressful control environment. Twoexperiments were carried out to measureproductivity (a multiplicative measure offecundity and viability) using a full factorialdesign. In the first experiment, productivitywas estimated for all lines and inbreedinglevels in the environment in which flies wereinbred and reared for several generations. Inthe second experiment, productivity of thelines reared in the control environment wastested in all four environments and for allinbreeding levels. Our results show asignificant effect of inbreeding andenvironmental stress on productivity in bothexperiments and the effect increased when flieswere exposed to novel environmental conditions.Productivity was not affected by theinteraction between inbreeding andenvironmental stress when flies were tested inthe environments in which they were reared,whereas there was a tendency towards a stressby inbreeding interaction when flies wereexposed to novel environments. The variance andthe coefficient of variation in productivitywere each affected by environmental stress andinbreeding, indicating that environmentalconditions as well as genetic background areimportant for variation in productivity.However, the two measures of variation oftenshowed opposite trends. The results obtained inthis study indicate that the environmentalconditions under which inbreeding occurs areimportant. This is relevant for the maintenanceand management of populations in captivity andin relation to reintroduction of endangeredspecies in nature.     

A Residue Quartet in the Extracellular Domain of the Prolactin Receptor Selectively Controls Mitogen-activated Protein Kinase Signaling

Cytokine receptors elicit several signaling pathways, but it is poorly understood how they select and discriminate between them. We have scrutinized the prolactin receptor as an archetype model of homodimeric cytokine receptors to address the role of the extracellular membrane proximal domain in signal transfer and pathway selection. Structure-guided manipulation of residues involved in the receptor dimerization interface identified one residue (position 170) that in cell-based assays profoundly altered pathway selectivity and species-specific bio-characteristics. Subsequent in vitro spectroscopic and nuclear magnetic resonance analyses revealed that this residue was part of a residue quartet responsible for specific local structural changes underlying these effects. This included alteration of a novel aromatic T-stack within the membrane proximal domain, which promoted selective signaling affecting primarily the MAPK (ERK1/2) pathway. Importantly, activation of the MAPK pathway correlated with in vitro stabilities of ternary ligand·receptor complexes, suggesting a threshold mean lifetime of the complex necessary to achieve maximal activation. No such dependence was observed for STAT5 signaling. Thus, this study establishes a residue quartet in the extracellular membrane proximal domain of homodimeric cytokine receptors as a key regulator of intracellular signaling discrimination.     

A new approach to functional interpretation of vegetation data

Abstract. In this paper we present a new approach to the simultaneous analysis of a species composition data set, an environmental gradient data set and a functional attribute data set. We demonstrate its advantages in terms of statistical modelling including model development and assessment as well as subsequent prediction. Our method is applied to a set of case data deriving from experimental wetland microcosms including 20 species, 12 treatment combinations and a classification of species into functional groups. Acknowledging that lack of independence between samples and over‐interpretation of data may lead to overly optimistic assessment of model performance, we use cross‐validation with different subsets of data to obtain realistic model performance measures. It is shown that although the outcome of the wetland experiment is predictable in terms of experimental treatments and taxo‐nomic species, the functional groups cannot be used to explain the variation in species frequencies in the experiment. We compare the method with recently published approaches to the functional analysis of vegetation data, and discuss its applied perspectives.     

Prediction of complex phenotypes using the Drosophila melanogaster metabolome

Understanding the genotype–phenotype map and how variation at different levels of biological organization is associated are central topics in modern biology. Fast developments in sequencing technologies and other molecular omic tools enable researchers to obtain detailed information on variation at DNA level and on intermediate endophenotypes, such as RNA, proteins and metabolites. This can facilitate our understanding of the link between genotypes and molecular and functional organismal phenotypes. Here, we use the Drosophila melanogaster Genetic Reference Panel and nuclear magnetic resonance (NMR) metabolomics to investigate the ability of the metabolome to predict organismal phenotypes. We performed NMR metabolomics on four replicate pools of male flies from each of 170 different isogenic lines. Our results show that metabolite profiles are variable among the investigated lines and that this variation is highly heritable. Second, we identify genes associated with metabolome variation. Third, using the metabolome gave better prediction accuracies than genomic information for four of five quantitative traits analyzed. Our comprehensive characterization of population-scale diversity of metabolomes and its genetic basis illustrates that metabolites have large potential as predictors of organismal phenotypes. This finding is of great importance, e.g., in human medicine, evolutionary biology and animal and plant breeding.Subject terms: Quantitative trait, Genetic association study     

The use of the oxidant"diamide" for studying the non-mitochondrial reducing capacity of Ehrlich ascites tumor cells

Diazenedicarboxylic acid bis(N,N-dimethylamide), (“diamide”) lowered non-mitochondrial NAD(P)H stores in Ehrlich ascites tumor cells in vitro by indirect reactions involving oxidation of glutathione and reduction of GSSG via glutathione reductase. The concentrations of diamide used did not alter the mitochondrial capacity to reduce NAD(P)H under anaerobic conditions. “Endogenous substrates” could be removed by multiple additions of diamide which indirectly inhibited NAD(P)H and GSH regeneration because of a lack of cellular reducing capacity. The regenerative power of the cells was restored by the addition of glucose. We conclude that diamide may prove to be a useful agent for studying the reducing capacity as well as the redox compartmentalization of cells in vitro.     

Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi

Background  

Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown.