Replica Exchange Molecular Dynamics Simulations Provide Insight into Substrate Recognition by Small Heat Shock Proteins

The small heat shock proteins (sHSPs) are a virtually ubiquitous and diverse group of molecular chaperones that can bind and protect unfolding proteins from irreversible aggregation. It has been suggested that intrinsic disorder of the N-terminal arm (NTA) of sHSPs is important for substrate recognition. To investigate conformations of the NTA that could recognize substrates we performed replica exchange molecular dynamics simulations. Behavior at normal and stress temperatures of the dimeric building blocks of dodecameric HSPs from wheat (Ta16.9) and pea (Ps18.1) were compared because they display high sequence similarity, but Ps18.1 is more efficient in binding specific substrates. In our simulations, the NTAs of the dimer are flexible and dynamic; however, rather than exhibiting highly extended conformations they retain considerable α-helical character and contacts with the conserved α-crystallin domain (ACD). Network analysis and clustering methods reveal that there are two major conformational forms designated either “open” or “closed” based on the relative position of the two NTAs and their hydrophobic solvent accessible surface area. The equilibrium constant for the closed to open transition is significantly different for Ta16.9 and Ps18.1, with the latter showing more open conformations at elevated temperature correlated with its more effective chaperone activity. In addition, the Ps18.1 NTAs have more hydrophobic solvent accessible surface than those of Ta16.9. NTA hydrophobic patches are comparable in size to the area buried in many protein-protein interactions, which would enable sHSPs to bind early unfolding intermediates. Reduced interactions of the Ps18.1 NTAs with each other and with the ACD contribute to the differences in dynamics and hydrophobic surface area of the two sHSPs. These data support a major role for the conformational equilibrium of the NTA in substrate binding and indicate features of the NTA that contribute to sHSP chaperone efficiency.     

Genetic characterization of congenital tufting enteropathy: epcam associated phenotype and involvement of SPINT2 in the syndromic form

Congenital tufting enteropathy (CTE) is a rare and severe enteropathy recently ascribed to mutations in the epcam gene. Here we establish SPINT2, previously ascribed to congenital sodium diarrhea, as a second gene associated with CTE and report molecular and immunohistochemistry data in 57 CTE patients. Inclusion criteria were early onset diarrhea and intestinal insufficiency with the typical histological CTE abnormalities. The clinical phenotype was registered, the entire coding regions of epcam and SPINT2 sequenced, and immunostaining of EpCAM and SPINT2 performed on intestinal biopsies. An epcam mutation was involved in 41 patients (73 %) who mainly displayed isolated digestive symptoms. Mutations severely affected gene expression since the EpCAM signal on intestinal tissues was either undetectable or low and irregular. Twelve other patients (21 %) carried mutations in SPINT2, and were phenotypically characterized by systematic association with keratitis (p < 10^?4) and, for half of them, with choanal atresia (p < 10^?4). Dependency on parenteral nutrition (PN) was comparable in patients with epcam or SPINT2 mutations, but the frequent epcam mutation c.556-14A>G (abnormal splicing) was significantly associated with a better outcome (p = 0.032) with milder PN dependency to weaning in some cases. Finally, four patients (7 %) with isolated digestive symptoms had no detectable epcam or SPINT2 mutation. Two candidate genes, Elf3 and Claudin7, were excluded from this population. Our study allows us to separate CTE patients into at least three genetic classes, each with specific phenotypes. The genetics approach raises the question of the distinction between two congenital enteropathies. Our findings should help improve the diagnosis of CTE, guide toward strategies of long-term PN management, and limit indications for intestinal transplantation to life-threatening PN complications.     

Two Biostimulants Derived from Algae or Humic Acid Induce Similar Responses in the Mineral Content and Gene Expression of Winter Oilseed Rape (Brassica napus L.)

Different strategies, known as crop biofortification, can be used to increase micronutrient concentrations in harvested parts to reduce nutrient deficiencies in the human diet. Apart from fertilization and genetic selection, a more environmentally friendly, less expensive, and more immediate solution could rely on the use of biostimulants derived from natural materials. Two biostimulants, AZAL5 and HA7, which are derived from seaweed and black peat, respectively, have been previously described as promoting growth of Brassica napus and having a substantial effect on gene expression. They were further studied to evaluate their effects on N and S and a wide range of other nutrients (that is, K, Ca, P, Mg, Fe, Na, Mn, B, Si, Cu, and Zn). Providing these two biostimulants in the nutrient solution did not change the mineral supply significantly, but they mostly stimulated root growth and macronutrient uptake (N, S, K, and P) at a level similar to growth. Both biostimulants also stimulate chloroplast division. More surprisingly, they also increased Mg, Mn, Na, and Cu plant concentrations and root-to-shoot translocation of Fe and Zn. These observations were associated with an increased expression of a Cu transporter (COPT2) and NRAMP3, a gene putatively involved in Fe and Zn translocation. Overall, this study showed that specific nutrient balance and transport were stimulated by both biostimulants more significantly than growth, offering new perspectives for biofortification strategies.     

Trace elements in tissues of white-chinned petrels (Procellaria aequinoctialis) from Kerguelen waters,Southern Indian Ocean

The use of seabirds to assess marine contamination by trace elements in areas remote from pollutant emission points has already been done at various latitudes. Nevertheless, little information is available concerning the Southern Indian Ocean. Determining the contaminants levels, there appears necessary not only due to several deleterious effects reported in literature, but also as previous studies have highlighted elevated concentrations of cadmium (Cd) and mercury (Hg) in mollusks, crustaceans and fish. Within this context, the white-chinned petrel appears as a key species due to its lifespan, diet and trophic position. Thirty-three accidentally killed (collision with lights/bycatch in longline vessels) individuals collected in Kerguelen waters were analysed for Cd, copper (Cu), Hg, selenium (Se) and zinc (Zn) in liver, kidney, pectoral muscle, feathers and for mature males, testis. Elevated Hg concentrations (average 58.4 μg g^?1 dw in liver) are likely due to the presence of mesopelagic prey in the diet of Procellaria aequinoctialis. Cd concentrations (average of 65.7 μg g^?1 dw in kidney) can be attributed to a high level of fisheries offal consumption, as well as crustacean and squid ingestion. Correlation of Hg with Se indicates its detoxification by co-precipitation, and correlation of Cd with Zn suggests its displacement by Cd on metallothioneins binding sites. This work also indirectly confirms ecological data (range and diet composition) from the wintering period of the species, which is rather scarce. Seasonal diet change and moulting accounted more for the obtained results than sex of the birds.     

Identification of key factors in Accelerated Low Water Corrosion through experimental simulation of tidal conditions: influence of stimulated indigenous microbiota

Biotic and abiotic factors favoring Accelerated Low Water Corrosion (ALWC) on harbor steel structures remain unclear warranting their study under controlled experimental tidal conditions. Initial stimulation of marine microbial consortia by a pulse of organic matter resulted in localized corrosion and the highest corrosion rates (up to 12-times higher than non-stimulated conditions) in the low water zone, persisting after nine months exposure to natural seawater. Correlations between corrosion severity and the abundance and composition of metabolically active sulfate-reducing bacteria (SRB) indicated the importance and persistence of specific bacterial populations in accelerated corrosion. One phylotype related to the electrogenic SRB Desulfopila corrodens appeared as the major causative agent of the accelerated corrosion. The similarity of bacterial populations related to sulfur and iron cycles, mineral and tuberculation with those identified in ALWC support the relevance of experimental simulation of tidal conditions in the management of steel corrosion exposed to harbor environments.     

Interaction of the Bioactive Flavonol,Icariin, with the Essential Human Solute Carrier Transporters

Solute carrier transporters (SLCs), in particular the organic anion transporting polypeptides (OATPs) and organic anion/cation transporters (OATs/OCTs), are responsible for the cellular entry of many clinically important drugs in body. They largely influence drug safety and efficacy. Icariin is a flavonol widely present in many herbal preparations, which is used to improve sexual function and prevent osteogenesis. However, precautions are necessary in therapies containing icariin due to its involvement in drug–drug/herb interactions, possibly mediated through competing drug uptake via membrane‐transporter proteins. This study is the first to comprehensively evaluate the interactions between icariin and a range of essential SLCs. Our data demonstrated that icariin can significantly inhibit OATP1B3‐ and OATP2B1‐mediated cellular uptake of specific substrates (IC₅₀ of 3.0 ± 1.3 and 6.4 ± 1.9 μM, respectively). Our study revealed that icariin can potentially compete with coadministrated drugs for particular SLCs, which may impact the therapeutic outcome of regimens.     

Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator

Environmental conditions can shape genetic and morphological divergence. Release of new habitats during historical environmental changes was a major driver of evolutionary diversification. Here, forces shaping population structure and ecotype differentiation (‘pelagic’ and ‘coastal’) of bottlenose dolphins in the North-east Atlantic were investigated using complementary evolutionary and ecological approaches. Inference of population demographic history using approximate Bayesian computation indicated that coastal populations were likely founded by the Atlantic pelagic population after the Last Glacial Maxima probably as a result of newly available coastal ecological niches. Pelagic dolphins from the Atlantic and the Mediterranean Sea likely diverged during a period of high productivity in the Mediterranean Sea. Genetic differentiation between coastal and pelagic ecotypes may be maintained by niche specializations, as indicated by stable isotope and stomach content analyses, and social behaviour. The two ecotypes were only weakly morphologically segregated in contrast to other parts of the World Ocean. This may be linked to weak contrasts between coastal and pelagic habitats and/or a relatively recent divergence. We suggest that ecological opportunity to specialize is a major driver of genetic and morphological divergence. Combining genetic, ecological and morphological approaches is essential to understanding the population structure of mobile and cryptic species.