Changes in metabolite profiles in Norway spruce shoot tips during short-day induced winter bud development and long-day induced bud flush

The seasonal change in photoperiod is a primary environmental signal influencing tree growth. Long days (LD) sustain growth, whereas short days (SD) induce winter bud formation. In this respect, metabolomic responses have been studied to a limited extent only in conifers. Here we identified changes in metabolite profile in the conifer Norway spruce after transition to SD and following re-transfer to LDs inducing bud flush. After 1 week in SD initial changes in metabolite profile was visible but for the majority of compounds magnitudes of changes were small. However, the ascorbate content was strongly reduced and there were often temporary increases in several energy metabolism-related compounds, secondary metabolites, nucleosides, amino acids and lipids. After 8 weeks in SD substantial changes were observed; proper winter buds had high pools of ABA, antioxidants, flavonoids, terpenoids, phenylpropanoids, sugars, amino acids and lipids related to stress tolerance and hardening, and low levels of nucleosides and metabolites in energy metabolism. One week after re-transfer to LD the metabolome was generally relatively similar to under long-term SD, except e.g. increased urate and strongly decreased ABA and oxidized glutathione. Two weeks later, bud flush had occurred, and the metabolite profile resembled the situation before transfer to SD. This study thus revealed comprehensive modulation of the metabolome in Norway spruce in response to a day length shift, indicating substantially increased stress resistance under SD-induced bud set, and reversal upon bud flush in LD.     

The effect of ecological and temporal factors on the composition of Bartonella infection in rodents and their fleas

The composition of Bartonella infection was explored in wild Gerbillus andersoni rodents and their Synosternus cleopatrae fleas. Rodent blood samples and fleas were collected in two periods (two different seasons; 4 months apart) from juveniles and adult hosts, and their bartonellae lineages were identified by a 454-pyrosequencing analysis targeting a specific Bartonella citrate synthase gene (gltA) fragment. The rate of Bartonella spp. co-infection was estimated and the assemblage and distribution of bartonellae lineages across the samples with respect to ecological and phylogenetic distance similarities were analyzed. Moreover, environmental factors that could explain potential differences between samples were investigated. Out of the 91 bartonellae-positive samples, 89% were found to be co-infected with more than two phylogenetically distant Bartonella genotypes and additional closely related (but distinguishable) variants. These bartonellae lineages were distributed in a non-random manner, and a negative interaction between lineages was discovered. Interestingly, the overall composition of those infections greatly varied among samples. This variability was partially explained by factors, such as type of sample (blood versus fleas), flea sex and period of collection. This investigation sheds light on the patterns of Bartonella infection and the organization of Bartonella lineages in fleas and rodents in nature.     

Invasive alien species under attack: natural enemies of Harmonia axyridis in the Netherlands

The aphid predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive alien species in Europe and North America with negative effects on non-target species (including a decline of native ladybird populations), as well as fruit production, and human health. It is, therefore, important to find out which natural enemies could be used to reduce their numbers. Knowledge of H. axyridis’ natural enemies is summarised and data collected from the Netherlands over the past ten years are presented. Beetles were sampled from winter aggregations and from spring through to autumn with illuminated screens at night. Natural enemies were not found in samples of H. axyridis from 2003–2007. From 2008 onward H. axyridis adults were infested by: Hesperomyces virescens Thaxt. fungi (summer and winter), Parasitylenchus bifurcatus Poinar and Steenberg nematodes (winter), Coccipolipus hippodamiae (McDaniel and Morrill) mites (winter), and Dinocampus coccinellae (Schrank) parasitoids (summer and winter). Our results indicate that these natural enemies are starting to use H. axyridis as a host, but are as yet not sufficiently abundant to control the population.     

Spatial distribution of diatom and cyanobacterial mats in the Dead Sea is determined by response to rapid salinity fluctuations

Cyanobacteria and diatom mats are ubiquitous in hypersaline environments but have never been observed in the Dead Sea, one of the most hypersaline lakes on Earth. Here we report the discovery of phototrophic microbial mats at underwater freshwater seeps in the Dead Sea. These mats are either dominated by diatoms or unicellular cyanobacteria and are spatially separated. Using in situ and ex situ O₂ microsensor measurements we show that these organisms are photosynthetically active in their natural habitat. The diatoms, which are phylogenetically associated to the Navicula genus, grew in culture at salinities up to 40 % Dead Sea water (DSW) (14 % total dissolved salts, TDS). The unicellular cyanobacteria belong to the extremely halotolerant Euhalothece genus and grew at salinities up to 70 % DSW (24.5 % TDS). As suggested by a variable O₂ penetration depth measured in situ, the organisms are exposed to drastic salinity fluctuations ranging from brackish to DSW salinity within minutes to hours. We could demonstrate that both phototrophs are able to withstand such extreme short-term fluctuations. Nevertheless, while the diatoms recover better from rapid fluctuations, the cyanobacteria cope better with long-term exposure to DSW. We conclude that the main reason for the development of these microbial mats is a local dilution of the hypersaline Dead Sea to levels allowing growth. Their spatial distribution in the seeping areas is a result of different recovery rates from short or long-term fluctuation in salinity.     

Circadian dysfunction in response to in?vivo treatment with the mitochondrial toxin 3-nitropropionic acid

Sleep disorders are common in neurodegenerative diseases including Huntington''s disease (HD) and develop early in the disease process. Mitochondrial alterations are believed to play a critical role in the pathophysiology of neurodegenerative diseases. In the present study, we evaluated the circadian system of mice after inhibiting mitochondrial complex II of the respiratory chain with the toxin 3-nitropropionic acid (3-NP). We found that a subset of mice treated with low doses of 3-NP exhibited severe circadian deficit in behavior. The temporal patterning of sleep behavior is also disrupted in some mice with evidence of difficulty in the initiation of sleep behavior. Using the open field test during the normal sleep phase, we found that the 3-NP-treated mice were hyperactive. The molecular clockwork responsible for the generation of circadian rhythms as measured by PER2::LUCIFERASE was disrupted in a subset of mice. Within the SCN, the 3-NP treatment resulted in a reduction in daytime firing rate in the subset of mice which had a behavioral deficit. Anatomically, we confirmed that all of the treated mice showed evidence for cell loss within the striatum but we did not see evidence for gross SCN pathology. Together, the data demonstrates that chronic treatment with low doses of the mitochondrial toxin 3-NP produced circadian deficits in a subset of treated mice. This work does raise the possibility that the neural damage produced by mitochondrial dysfunction can contribute to the sleep/circadian dysfunction seen so commonly in neurodegenerative diseases.     

NMR assignments of a hypothetical pseudo-knotted protein HP0242 from Helicobacter pylori

Many knotted proteins have been discovered recently, but the folding process of which remains elusive. HP0242 is a hypothetical protein from Helicobacter pylori, which is a model system for studying the folding pathway of a knotted protein. In this study, we report the ¹H, ¹³C, and ¹⁵N chemical shift assignments of HP0242. The results will enable us to further investigate HP0242 by NMR experiments.