The effect of drought stress on heterozygosity–fitness correlations in pedunculate oak (Quercus robur)

Background and Aims

The interaction between forest fragmentation and predicted climate change may pose a serious threat to tree populations. In small and spatially isolated forest fragments, increased homozygosity may directly affect individual tree fitness through the expression of deleterious alleles. Climate change-induced drought stress may exacerbate these detrimental genetic consequences of forest fragmentation, as the fitness response to low levels of individual heterozygosity is generally thought to be stronger under environmental stress than under optimal conditions.

Methods

To test this hypothesis, a greenhouse experiment was performed in which various transpiration and growth traits of 6-month-old seedlings of Quercus robur differing in multilocus heterozygosity (MLH) were recorded for 3 months under a well-watered and a drought stress treatment. Heterozygosity–fitness correlations (HFC) were examined by correlating the recorded traits of individual seedlings to their MLH and by studying their response to drought stress.

Key Results

Weak, but significant, effects of MLH on several fitness traits were obtained, which were stronger for transpiration variables than for the recorded growth traits. High atmospheric stress (measured as vapour pressure deficit) influenced the strength of the HFCs of the transpiration variables, whereas only a limited effect of the irrigation treatment on the HFCs was observed.

Conclusions

Under ongoing climate change, increased atmospheric stress in the future may strengthen the negative fitness responses of trees to low MLH. This indicates the necessity to maximize individual multilocus heterozygosity in forest tree breeding programmes.     

Coronary vasoconstrictor influence of angiotensin II is reduced in remodeled myocardium after myocardial infarction

The renin-angiotensin system plays an important role in cardiovascular homeostasis by contributing to the regulation of blood volume, blood pressure, and vascular tone. Because AT(1) receptors have been described in the coronary microcirculation, we investigated whether ANG II contributes to the regulation of coronary vascular tone and whether its contribution is altered during exercise. Since the renin-angiotensin system is activated after myocardial infarction, resulting in an increase in circulating ANG II, we also investigated whether the contribution of ANG II to the regulation of vasomotor tone is altered after infarction. Twenty-six chronically instrumented swine were studied at rest and while running on a treadmill at 1-4 km/h. In 13 swine, myocardial infarction was induced by ligation of the left circumflex coronary artery. Blockade of AT(1) receptors (irbesartan, 1 mg/kg iv) had no effect on myocardial O(2) consumption but resulted in an increase in coronary venous O(2) tension and saturation both at rest and during exercise, reflecting coronary vasodilation. Despite increased plasma levels of ANG II after infarction and maintained coronary arteriolar AT(1) receptor levels, the vasodilation evoked by irbesartan was significantly reduced both at rest and during exercise. In conclusion, despite elevated plasma levels, the vasoconstrictor influence of ANG II on the coronary circulation in vivo is reduced after myocardial infarction. This reduction in ANG II-induced coronary vasoconstriction may serve to maintain perfusion of the remodeled myocardium.     

Climate warming and atmospheric deposition affect seed viability of common juniper (<Emphasis Type="Italic">Juniperus communis</Emphasis>) via their impact on the nutrient status of the plant

Global environmental change is increasingly affecting species worldwide. One of the emblematic casualties among plants in several European countries is common juniper (Juniperus communis). Many populations of common juniper throughout its distribution range are declining. The relative lack of viable seed production, resulting in low probabilities for successful natural regeneration, is one of the main reasons for this decline. Climate warming and elevated atmospheric depositions have been shown to negatively affect seed viability of common juniper, but our understanding of the underlying mechanisms remains scarce. One possible pathway is via changes in the plant nutrient status that, in turn, may affect seed viability. Here we took advantage of large-scale gradients in climate and atmospheric depositions between central Sweden and northern Spain, and analysed foliar nutrient concentrations and stoichiometry and seed viability in 20 juniper populations spread across Europe. Our results show that increasing temperatures can negatively affect needle N and P concentrations while enhanced potentially acidifying depositions resulted in lower foliar N and Ca concentrations. Needle C:N ratios increased with higher temperature, acidifying depositions and precipitation. By linking these patterns to seed viability, we found that low needle P, Ca and Mg concentrations were related to low seed viability. Thus, a shortage of these key elements during seed development and seed nutrient storage, can lead to anomalies and seed abortion. These findings help to explain the low seed viability of juniper in Europe and may help to assist land managers to take urgently needed conservation actions.     

Evoked Emotions Predict Food Choice

In the current study we show that non-verbal food-evoked emotion scores significantly improve food choice prediction over merely liking scores. Previous research has shown that liking measures correlate with choice. However, liking is no strong predictor for food choice in real life environments. Therefore, the focus within recent studies shifted towards using emotion-profiling methods that successfully can discriminate between products that are equally liked. However, it is unclear how well scores from emotion-profiling methods predict actual food choice and/or consumption. To test this, we proposed to decompose emotion scores into valence and arousal scores using Principal Component Analysis (PCA) and apply Multinomial Logit Models (MLM) to estimate food choice using liking, valence, and arousal as possible predictors. For this analysis, we used an existing data set comprised of liking and food-evoked emotions scores from 123 participants, who rated 7 unlabeled breakfast drinks. Liking scores were measured using a 100-mm visual analogue scale, while food-evoked emotions were measured using 2 existing emotion-profiling methods: a verbal and a non-verbal method (EsSense Profile and PrEmo, respectively). After 7 days, participants were asked to choose 1 breakfast drink from the experiment to consume during breakfast in a simulated restaurant environment. Cross validation showed that we were able to correctly predict individualized food choice (1 out of 7 products) for over 50% of the participants. This number increased to nearly 80% when looking at the top 2 candidates. Model comparisons showed that evoked emotions better predict food choice than perceived liking alone. However, the strongest predictive strength was achieved by the combination of evoked emotions and liking. Furthermore we showed that non-verbal food-evoked emotion scores more accurately predict food choice than verbal food-evoked emotions scores.     

Accurate SNP and mutation detection by targeted custom microarray-based genomic enrichment of short-fragment sequencing libraries

Microarray-based enrichment of selected genomic loci is a powerful method for genome complexity reduction for next-generation sequencing. Since the vast majority of exons in vertebrate genomes are smaller than 150 nt, we explored the use of short fragment libraries (85–110 bp) to achieve higher enrichment specificity by reducing carryover and adverse effects of flanking intronic sequences. High enrichment specificity (60–75%) was obtained with a relative even base coverage. Up to 98% of the target-sequence was covered more than 20× at an average coverage depth of about 200×. To verify the accuracy of SNP/mutation detection, we evaluated 384 known non-reference SNPs in the targeted regions. At ∼200× average sequence coverage, we were able to survey 96.4% of 1.69 Mb of genomic sequence with only 4.2% false negative calls, mostly due to low coverage. Using the same settings, a total of 1197 novel candidate variants were detected. Verification experiments revealed only eight false positive calls, indicating an overall false positive rate of less than 1 per ∼200 000 bp. Taken together, short fragment libraries provide highly efficient and flexible enrichment of exonic targets and yield relatively even base coverage, which facilitates accurate SNP and mutation detection. Raw sequencing data, alignment files and called SNPs have been submitted into GEO database http://www.ncbi.nlm.nih.gov/geo/ with accession number {"type":"entrez-geo","attrs":{"text":"GSE18542","term_id":"18542"}}GSE18542.     

Initiation of replication in the Chinese hamster dihydrofolate reductase domain

Two-dimensional (2-D) gel analysis of replication intermediates in the Chinese hamster dihydrofolate reductase domain has suggested that nascent chains can initiate at any of a large number of sites scattered throughout a ～50 kb “initiation locus” (although the level of initiation detected at any given site within this region was relatively low). This result contrasts markedly with data from anin vitro strand switching assay suggesting that >80% of initiations occur within a single 500 bp fragment lying within the initiation locus. In an effort to reconcile these two disparate views of the initiation reaction, we have questioned the validity of our 2-D gel data in several ways. We show here that: 1) the number of replication bubbles detected in the DHFR locus in the early S period is markedly increased when the cells are released from a synchronizing agent that inhibits initiationper se, rather than from aphidicolin, which is a chain elongation inhibitor; 2) initiation in the DHFR domain occurs only during the first 90 min of the S period, as would be expected of an early-firing origin; 3) a pulse of³H-thymidine moves through the structures observed on 2-D gels with the kinetics expected ofbonafide replication intermediates; and 4) preparations of replication intermediates that are subsequently analyzed on 2-D gels appear, by electron microscopy, to represent the typical theta structures and single-forked molecules expected of bidirectional origins of replication; no unusual structures (e.g., microbubbles) were seen.     

Dark states in monomeric red fluorescent proteins studied by fluorescence correlation and single molecule spectroscopy

Monomeric red fluorescent proteins (mRFPs) have become indispensable tools for studying protein dynamics, interactions and functions in the cellular environment. Their emission spectrum can be well separated from other fluorescent proteins, and their monomeric structure preserves the natural function of fusion proteins. However, previous photophysical studies of some RFPs have shown the presence of light-induced dark states that can complicate the interpretation of cellular experiments. In this article, we extend these studies to mRFP1, mCherry, and mStrawberry by means of fluorescence correlation spectroscopy and prove that this light-driven intensity flickering also occurs in these proteins. Furthermore, we show that the flickering in these proteins is pH-dependent. Single molecule spectroscopy revealed reversible transitions from a bright to a dark state in several timescales, even up to seconds. Time-resolved fluorescence spectroscopy showed multiexponential decays, consistent with a “loose” conformation. We offer a structural basis for the fluorescence flickering using known crystal structures and point out that the environment of Glu-215 is critical for the pH dependence of the flickering in RFPs. We apply dual-color fluorescence correlation spectroscopy inside live cells to prove that this flickering can seriously hamper cellular measurements if the timescales of the flickering and diffusion are not well separated.     

Ant Queen Egg-Marking Signals: Matching Deceptive Laboratory Simplicity with Natural Complexity

Background

Experiments under controlled laboratory conditions can produce decisive evidence for testing biological hypotheses, provided they are representative of the more complex natural conditions. However, whether this requirement is fulfilled is seldom tested explicitly. Here we provide a lab/field comparison to investigate the identity of an egg-marking signal of ant queens. Our study was based on ant workers resolving conflict over male production by destroying each other''s eggs, but leaving queen eggs unharmed. For this, the workers need a proximate cue to discriminate between the two egg types. Earlier correlative evidence indicated that, in the ant Pachycondyla inversa, the hydrocarbon 3,11-dimethylheptacosane (3,11-diMeC₂₇) is more abundant on the surface of queen-laid eggs.

Methodology

We first tested the hypothesis that 3,11-diMeC₂₇ functions as a queen egg-marking pheromone using laboratory-maintained colonies. We treated worker-laid eggs with synthetic 3,11-diMeC₂₇ and found that they were significantly more accepted than sham-treated worker-laid eggs. However, we repeated the experiment with freshly collected field colonies and observed no effect of treating worker-laid eggs with 3,11-diMeC₂₇, showing that this compound by itself is not the natural queen egg-marking pheromone. We subsequently investigated the overall differences of entire chemical profiles of eggs, and found that queen-laid eggs in field colonies are more distinct from worker-laid eggs than in lab colonies, have more variation in profiles, and have an excess of longer-chain hydrocarbons.

Conclusions

Our results suggest that queen egg-marking signals are significantly affected by transfer to the laboratory, and that this change is possibly connected to reduced queen fertility as predicted by honest signaling theory. This change is reflected in the worker egg policing response under field and laboratory conditions.     

Imidazo[1,2-α]pyridines possess adenosine A1 receptor affinity for the potential treatment of cognition in neurological disorders

Previous research has shown that bicyclic 6:5-fused heteroaromatic compounds with two N-atoms have variable degrees of adenosine A₁ receptor antagonistic activity. Prompted by this imidazo[1,2-α]pyridine analogues were synthesized and evaluated for their adenosine A₁ and A_2A receptor affinity via radioligand binding studies and subjected to a GTP shift assay to determine its adenosine A₁ receptor agonistic or antagonistic functionality. Imidazo[1,2-α]pyridine, the parent scaffold, was found devoid of affinity for the adenosine A₁ and A_2A receptors. The influence of substitution on position C2 showed no improvement for either adenosine A₁ or A_2A receptor affinity. The addition of an amino or a cyclohexylamino group to position C3 also showed no improvement of adenosine A₁ or A_2A receptor affinity. Surprisingly para-substitution on the phenyl ring at position C2 in combination with a cyclohexylamino group at position C3 led to adenosine A₁ receptor affinity in the low micromolar range with compound 4d showing: (1) the highest affinity for the adenosine A₁ receptor with a K_i value of 2.06 µM and (2) adenosine A₁ receptor antagonistic properties. This pilot study concludes that para-substituted 3-cyclohexylamino-2-phenyl-imidazo[1,2-α]pyridine analogues represent an interesting scaffold to investigate further structure-activity relationships in the design of novel imidazo[1,2-α]pyridine-based adenosine A₁ receptor antagonists for the treatment of neurodegenerative disorders.