Could root-excreted iron ligands contribute to cadmium and zinc uptake by the hyperaccumulator Noccaea caerulescens?

Plant and Soil - Evaluation of various mechanisms of Cd2+ and Zn2+ root uptake through modelling, including interactions with Fe uptake. Four increasingly complex models were developed and tested...     

Does Speciation between Arabidopsis halleri and Arabidopsis lyrata Coincide with Major Changes in a Molecular Target of Adaptation?

Ever since Darwin proposed natural selection as the driving force for the origin of species, the role of adaptive processes in speciation has remained controversial. In particular, a largely unsolved issue is whether key divergent ecological adaptations are associated with speciation events or evolve secondarily within sister species after the split. The plant Arabidopsis halleri is one of the few species able to colonize soils highly enriched in zinc and cadmium. Recent advances in the molecular genetics of adaptation show that the physiology of this derived ecological trait involves copy number expansions of the AhHMA4 gene, for which orthologs are found in single copy in the closely related A. lyrata and the outgroup A. thaliana. To gain insight into the speciation process, we ask whether adaptive molecular changes at this candidate gene were contemporary with important stages of the speciation process. We first inferred the scenario and timescale of speciation by comparing patterns of variation across the genomic backgrounds of A. halleri and A. lyrata. Then, we estimated the timing of the first duplication of AhHMA4 in A. halleri. Our analysis suggests that the historical split between the two species closely coincides with major changes in this molecular target of adaptation in the A. halleri lineage. These results clearly indicate that these changes evolved in A. halleri well before industrial activities fostered the spread of Zn- and Cd-polluted areas, and suggest that adaptive processes related to heavy-metal homeostasis played a major role in the speciation process.     

Does myoglobin protect Trypanosoma cruzi from the antiparasitic effects of nitric oxide?

The hemoflagellate protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, a progressive fatal cardiomyopathy widespread in South and Central America. Here, we postulate that the preferential colonization of cardiomyocytes by T. cruzi may reflect the role of myoglobin (Mb) as a nitric oxide (NO) scavenger, protecting the parasite from the trypanocidal effects of NO. The proposal of this novel function of Mb is based on knowledge that ferrous oxygenated Mb reacts rapidly and irreversibly with NO yielding nitrate and ferric oxidized Mb, which is reduced back to the physiologically active form by an intracellular reductase. The postulated protective role of Mb on the viability of T. cruzi is reminiscent of that postulated for hemoglobin in protecting intraerythrocytic Plasmodia from the parasiticidal effect of NO.     

Does CK2 affect flowering time by modulating the autonomous pathway in Arabidopsis?

CK2 (Casein kinase II), a ubiquitous Ser/Thr kinase, affects multiple developmental and stress response pathways in Arabidopsis, including flowering time under both long- and short-day conditions through the photoperiod and autonomous pathways. CK2 phosphorylates central clock components, CCA1 and LHY, to modulate circadian clock that regulates flowering time through the photoperiod pathway. However, how CK2 regulates flowering time through the autonomous pathway is still unknown. Analyses of phosphorylation sites using several prediction softwares show that most of the autonomous pathway components have multiple CK2 phosphorylation sites. CK2 might phosphorylate any or all of these components to modulate their activity/stability resulting in altered expression of FLC that drives flowering time through the autonomous pathway.     

Can sulci protect the brain from traumatic injury?

The influence of sulci in dynamic finite element simulations of the human head has been investigated. First, a detailed 3D FE model was constructed based on an MRI scan of a human head. A second model with a smoothed brain surface was created based on the same MRI scan as the first FE model. These models were validated against experimental data to confirm their human-like dynamic responses during impact. The validated FE models were subjected to several acceleration impulses and the maximum principle strain and strain rate in the brain were analyzed. The results suggested that the inclusion of sulci should be considered for future FE head models as it alters the strain and strain distribution in an FE model.     

Does photorespiration protect the photosynthetic apparatus in french bean leaves from photoinhibition during drought stress?

Dithiothreitol (DTT), an inhibitor of violaxanthin de-epoxidation and zeaxanthin formation in chloroplasts, inhibited blue-light-stimulated stomatal opening in epidermal peels of Vicia faba L. in a concentration-dependent fashion. Complete inhibition was observed at 3 mM DTT. The DTT effect was specific for the stomatal response to blue light, and the red-light-stimulated opening, which depends on photosynthetic reactions in the guard cells, was unaffected. Preirradiation of stomata in epidermal peels with increasing photon fluence rates of red light, prior to an incubation in 10 mol·m^-2·s^-1 of blue light and 100 mol·m^-2·s^-1 red light, resulted in a DTT-sensitive, blue-light-stimulated opening that was proportional to the fluence rate of the red light pre-treatment. Guard cells in epidermal peels and guard-cell protoplasts irradiated with red light showed increases in their zeaxanthin content that depended on the fluence rate of red light, or on the incubation time. The increases in zeaxanthin concentration were inhibited by DTT. The obtained results indicate that zeaxanthin could function as a photoreceptor mediating the stomatal responses to blue light.Abbreviation DTT dithiothreitol This work was supported by grants from the National Science Foundation and the US Department of Energy to E.Z.     

Does insect herbivory on oak depend on the diversity of tree stands?

Studies on the effects of plant diversity on insect herbivory have produced conflicting results. Plant diversity has been reported to cause positive and negative responses of herbivores. Explanations for these conflicting responses include not only various population-level processes but also changes in plant quality that lead to changes in herbivore performance. In a tree diversity experiment, we investigated the effects of tree diversity on insect herbivory on oak in general and whether the effects of tree diversity on herbivore damage are reflected by the performance (leaf consumption, growth) of the generalist herbivore Lymantria dispar. Our study showed that the feeding damage caused by naturally occurring herbivores on oak trees decreased with increasing diversity of tree stands. The performance of L. dispar on oak leaves was not affected by tree diversity, neither in field nor laboratory experiments. Our results can be explained by the various processes behind the hypothesis of associational resistance.     

Does isoprene protect plant membranes from thermal shock? A molecular dynamics study

The question of why plants release isoprene when heat stressed has been continuously debated for more than half a century. In this work we use molecular dynamics simulation techniques to directly investigate the interaction between isoprene and a model phospholipid membrane in atomic detail. It is found that isoprene partitions preferentially in the center of the membrane and in a dose dependent manner enhances the order within the membrane without significantly changing the dynamical properties of the system. At a concentration of 20 mol% isoprene (16 isoprene molecules per 64 lipid molecules) the effect of the addition of isoprene on the membrane order is equivalent to a reduction in temperature of 10 K, rising to a reduction of 30 K at 43 mol% isoprene. The significance of the work is that it provides for the first time direct evidence that isoprene stabilizes lipid membranes and reduces the likelihood of a phospholipid membrane undergoing a heat induced phase transition. Furthermore it provides a clear mechanistic picture as to why plants specifically utilize isoprene for this purpose.     

Does isoprene protect plant membranes from thermal shock? A molecular dynamics study

The question of why plants release isoprene when heat stressed has been continuously debated for more than half a century. In this work we use molecular dynamics simulation techniques to directly investigate the interaction between isoprene and a model phospholipid membrane in atomic detail. It is found that isoprene partitions preferentially in the center of the membrane and in a dose dependent manner enhances the order within the membrane without significantly changing the dynamical properties of the system. At a concentration of 20 mol% isoprene (16 isoprene molecules per 64 lipid molecules) the effect of the addition of isoprene on the membrane order is equivalent to a reduction in temperature of 10 K, rising to a reduction of 30 K at 43 mol% isoprene. The significance of the work is that it provides for the first time direct evidence that isoprene stabilizes lipid membranes and reduces the likelihood of a phospholipid membrane undergoing a heat induced phase transition. Furthermore it provides a clear mechanistic picture as to why plants specifically utilize isoprene for this purpose.     

Does isometamidium chloride treatment protect tsetse flies from trypanosome infections during SIT campaigns?

African animal trypanosomosis is a major pathological constraint to cattle breeding across 10 million km2 of sub-Saharan West African countries infested by tsetse flies, their cyclic vectors. The release of sterile males (sterile insect technique [SIT]) is a potentially important control technique aimed at eliminating the vectors. Prior to release, tsetse are generally treated with isometamidium chloride, a trypanocide, to prevent them from transmitting parasites. The present study investigated the preventive action of isometamidium chloride (0.5 mg/L) on the subsequent susceptibility of tsetse released into the wild. A total of 1755 Glossina palpalis gambiensis Vanderplank and 744 Glossina tachinoides Westwood were released, of which 50 and 48, respectively, were recaptured 22-43 days after release. Their probosces were analysed by polymerase chain reaction to identify mature infections with three trypanosome species (Trypanosoma vivax, Trypanosoma brucei sensu lato and Trypanosoma congolense savannah type). Two mature infections with T. vivax and four with T. congolense were detected, indicating that the use of this treatment regimen in an SIT campaign would not totally prevent sterile males from transmitting trypanosomes.     

Does elevated CO2 protect photosynthesis from damage by high temperature via modifying leaf water status in maize seedlings?

We hypothesized that decreased stomatal conductance (g _s) at elevated CO₂ might decrease transpiration (E), increase leaf water potential (Ψ_W), and thereby protect net photosynthesis rate (P _N) from heat damage in maize (Zea mays L) seedlings. To separate long-term effects of elevated CO₂, plants grew at either ambient CO₂ or elevated CO₂. During high-temperature treatment (HT) at 45°C for 15 min, leaves were exposed either to ambient CO₂ (380 μmol mol^?1) or to elevated CO₂ (560 μmol mol^?1). HT reduced P _N by 25 to 38% across four CO₂ combinations. However, the g _s and E did not differ among all CO₂ treatments during HT. After returning the leaf temperature to 35°C within 30 min, g _s and E were the same or higher than the initial values. Leaf water potential (Ψ_W) was slightly lower at ambient CO₂, but not at elevated CO₂. This study highlighted that elevated CO₂ failed in protecting P _N from 45°C via decreasing g _s and Ψ_W.     

Does vitamin D protect against DNA damage?

Vitamin D is a secosteroid best known for its role in maintaining bone and muscle health. Adequate levels of vitamin D may also be beneficial in maintaining DNA integrity. This role of vitamin D can be divided into a primary function that prevents damage from DNA and a secondary function that regulates the growth rate of cells. The potential for vitamin D to reduce oxidative damage to DNA in a human has been suggested by clinical trial where vitamin D supplementation reduced 8-hydroxy-2'-deoxyguanosine, a marker of oxidative damage, in colorectal epithelial crypt cells. Studies in animal models and in different cell types have also shown marked reduction in oxidative stress damage and chromosomal aberrations, prevention of telomere shortening and inhibition of telomerase activity following treatment with vitamin D. The secondary function of vitamin D in preventing DNA damage includes regulation of the poly-ADP-ribose polymerase activity in the DNA damage response pathway involved in the detection of DNA lesions. It is also able to regulate the cell cycle to prevent the propagation of damaged DNA, and to regulate apoptosis to promote cell death. Vitamin D may contribute to prevention of human colorectal cancer, though there is little evidence to suggest that prevention of DNA damage mediates this effect, if real. Very limited human data mean that the intake of vitamin D required to minimise DNA damage remains uncertain.     

Does a redox cycle provide a mechanism for setting the capacity of neuroglobin to protect cells from apoptosis?

We hypothesize that the various, previously reported, reactivities of neuroglobin with redox partners and oxygen provide for the establishment of a redox cycle within cells, such as neurons and retinal rod cells. Using native cell lysates, from cultured human cells of neuronal origin, we have estimated the rate of reduction of the oxidized form of neuroglobin in vivo. Furthermore we provide evidence that the cytosol of these cells contains factors (presumably enzymes) capable of employing either glutathione or NADH as re-reductants of ferric neuroglobin. Taken in conjunction with previous rate data, for the various redox reactions of neuroglobin, this information allows us to set up a computer model to estimate the steady state cellular level of the antiapoptotic ferrous form of neuroglobin. This model indicates that the steady state level of antiapoptotic neuroglobin is very sensitive to the cellular oxygen tension and moderately sensitive to the redox status of the cell. Further analysis indicates that such a system would be capable of significant modification, on the seconds time scale, following hypoxic transition, as is likely in stroke. We hypothesize that this mechanism might provide a moderately rapid mechanism for adjusting the antiapoptotic status of a cell, whilst the reaction of neuroglobin with mitochondrial cytochrome c provides a very rapid, but limited, capacity to intervene in the apoptotic pathway.     

Does behavioural fever occur in snails parasitised with trematode larvae?

The objective of this study was to determine whether individuals of Lymnaea stagnalis naturally parasitised with trematode larvae had different thermal preferences from non-parasitised ones, and what was the influence of constant temperature on biology of the host and the parasite.

The snails under study were placed in and oblong thermal gradient and their preferences were recorded during 24 h. Non-parasitised individuals chose a rather high temperature (25 °C). In the group of parasitised snails, only individuals which released cercariae showed statistically significant differences in thermal preference than the non-larvae releasing ones. Parasitised snails kept in constant temperatures lived shorter than non-parasitised ones. At high temperatures, they released more cercariae per day than at low temperatures. Temperature had a great influence on the longevity and viability of cercariae.

The thermal behaviour of snails parasitised with trematode larvae is not a symptom of behavioural fever but probably can play a therapeutic role in the host.