Development of gene expression markers of acute heat-light stress in reef-building corals of the genus Porites

Coral reefs are declining worldwide due to increased incidence of climate-induced coral bleaching, which will have widespread biodiversity and economic impacts. A simple method to measure the sub-bleaching level of heat-light stress experienced by corals would greatly inform reef management practices by making it possible to assess the distribution of bleaching risks among individual reef sites. Gene expression analysis based on quantitative PCR (qPCR) can be used as a diagnostic tool to determine coral condition in situ. We evaluated the expression of 13 candidate genes during heat-light stress in a common Caribbean coral Porites astreoides, and observed strong and consistent changes in gene expression in two independent experiments. Furthermore, we found that the apparent return to baseline expression levels during a recovery phase was rapid, despite visible signs of colony bleaching. We show that the response to acute heat-light stress in P. astreoides can be monitored by measuring the difference in expression of only two genes: Hsp16 and actin. We demonstrate that this assay discriminates between corals sampled from two field sites experiencing different temperatures. We also show that the assay is applicable to an Indo-Pacific congener, P. lobata, and therefore could potentially be used to diagnose acute heat-light stress on coral reefs worldwide.     

Heavy Chain-Only IgG2b Llama Antibody Effects Near-Pan HIV-1 Neutralization by Recognizing a CD4-Induced Epitope That Includes Elements of Coreceptor- and CD4-Binding Sites

The conserved HIV-1 site of coreceptor binding is protected from antibody-directed neutralization by conformational and steric restrictions. While inaccessible to most human antibodies, the coreceptor site has been shown to be accessed by antibody fragments. In this study, we used X-ray crystallography, surface plasmon resonance, and pseudovirus neutralization to characterize the gp120-envelope glycoprotein recognition and HIV-1 neutralization of a heavy chain-only llama antibody, named JM4. We describe full-length IgG2b and IgG3 versions of JM4 that target the coreceptor-binding site and potently neutralize over 95% of circulating HIV-1 isolates. Contrary to established trends that show improved access to the coreceptor-binding region by smaller antibody fragments, the single-domain (VHH) version of JM4 neutralized less well than the full-length IgG2b version of JM4. The crystal structure at 2.1-Å resolution of VHH JM4 bound to HIV-1 YU2 gp120 stabilized in the CD4-bound state by the CD4-mimetic miniprotein, M48U1, revealed a JM4 epitope that combined regions of coreceptor recognition (including the gp120 bridging sheet, V3 loop, and β19 strand) with gp120 structural elements involved in recognition of CD4 such as the CD4-binding loop. The structure of JM4 with gp120 thus defines a novel CD4-induced site of vulnerability involving elements of both coreceptor- and CD4-binding sites. The potently neutralizing JM4 IgG2b antibody that targets this newly defined site of vulnerability adds to the expanding repertoire of broadly neutralizing antibodies that effectively neutralize HIV-1 and thereby potentially provides a new template for vaccine development and target for HIV-1 therapy.     

Fluorescence of coral larvae predicts their settlement response to crustose coralline algae and reflects stress

Multi-coloured homologues of the green fluorescent protein generate some of the most striking visual phenomena in the ocean. Despite their natural prominence in reef-building corals and widespread use in biotechnology, their biological role remains obscure. Here, we experimented with larvae of Acropora millepora to determine what can be learned about a coral larva or recruit from its fluorescent colour. We performed 12 crosses between seven A. millepora colonies representing differing fluorescence phenotypes, the larvae of which were exposed to a natural settlement cue (crustose coralline algae) and heat-light stress. Parental effects explained 18 per cent of variation in colour and 47 per cent of variation in settlement. The colour of the larval family emerged as a predictor of the settlement success: redder families were significantly less responsive to the provided settlement cue (p = 0.006). This relationship was owing to a correlation between parental effects on settlement and colour (r(2) = 0.587, p = 0.045). We also observed pronounced (16%) decline in settlement rate, as well as subtle (2%), but a statistically significant decrease in red fluorescence, as a consequence of heat-light stress exposure. Variation in settlement propensity in A. millepora is largely owing to additive genetic effects, and is thought to reflect variation in dispersal potential. Our results suggest an optical signature to discriminate between long- and short-range dispersing genotypes, as well as to evaluate stress. Further research in this direction may lead to the development of field applications to trace changes in coral life history and physiology caused by global warming.     

Recruit symbiosis establishment and Symbiodiniaceae composition influenced by adult corals and reef sediment

Coral Reefs - For most reef-building corals, the establishment of symbiosis occurs via horizontal transmission, where juvenile coral recruits acquire their algal symbionts (family Symbiodiniaceae)...     

Identification of new Presenilin‐1 phosphosites: implication for γ‐secretase activity and Aβ production

An important pathological hallmark of Alzheimer's disease (AD) is the deposition of amyloid‐beta (Aβ) peptides in the brain parenchyma, leading to neuronal death and impaired learning and memory. The protease γ‐secretase is responsible for the intramembrane proteolysis of the amyloid‐β precursor protein (APP), which leads to the production of the toxic Aβ peptides. Thus, an attractive therapeutic strategy to treat AD is the modulation of the γ‐secretase activity, to reduce Aβ42 production. Because phosphorylation of proteins is a post‐translational modification known to modulate the activity of many different enzymes, we used electrospray (LC‐MS/MS) mass spectrometry to identify new phosphosites on highly purified human γ‐secretase. We identified 11 new single or double phosphosites in two well‐defined domains of Presenilin‐1 (PS1), the catalytic subunit of the γ‐secretase complex. Next, mutagenesis and biochemical approaches were used to investigate the role of each phosphosite in the maturation and activity of γ‐secretase. Together, our results suggest that the newly identified phosphorylation sites in PS1 do not modulate γ‐secretase activity and the production of the Alzheimer's Aβ peptides. Individual PS1 phosphosites shall probably not be considered therapeutic targets for reducing cerebral Aβ plaque formation in AD.

     

Seagrasses are negatively affected by organic matter loading and Arenicola marina activity in a laboratory experiment

When two ecosystem engineers share the same natural environment, the outcome of their interaction will be unclear if they have contrasting habitat-modifying effects (e.g., sediment stabilization vs. sediment destabilization). The outcome of the interaction may depend on local environmental conditions such as season or sediment type, which may affect the extent and type of habitat modification by the ecosystem engineers involved. We mechanistically studied the interaction between the sediment-stabilizing seagrass Zostera noltii and the bioturbating and sediment-destabilizing lugworm Arenicola marina, which sometimes co-occur for prolonged periods. We investigated (1) if the negative sediment destabilization effect of A. marina on Z. noltii might be counteracted by positive biogeochemical effects of bioirrigation (burrow flushing) by A. marina in sulfide-rich sediments, and (2) if previously observed nutrient release by A. marina bioirrigation could affect seagrasses. We tested the individual and combined effects of A. marina presence and high porewater sulfide concentrations (induced by organic matter addition) on seagrass biomass in a full factorial lab experiment. Contrary to our expectations, we did not find an effect of A. marina on porewater sulfide concentrations. A. marina activities affected the seagrass physically as well as by pumping nutrients, mainly ammonium and phosphate, from the porewater to the surface water, which promoted epiphyte growth on seagrass leaves in our experimental set-up. We conclude that A. marina bioirrigation did not alleviate sulfide stress to seagrasses. Instead, we found synergistic negative effects of the presence of A. marina and high sediment sulfide levels on seagrass biomass.     

Common variants in the type 2 diabetes KCNQ1 gene are associated with impairments in insulin secretion during hyperglycaemic glucose clamp

Background

Genome-wide association studies in Japanese populations recently identified common variants in the KCNQ1 gene to be associated with type 2 diabetes. We examined the association of these variants within KCNQ1 with type 2 diabetes in a Dutch population, investigated their effects on insulin secretion and metabolic traits and on the risk of developing complications in type 2 diabetes patients.

Methodology

The KCNQ1 variants rs151290, rs2237892, and rs2237895 were genotyped in a total of 4620 type 2 diabetes patients and 5285 healthy controls from the Netherlands. Data on macrovascular complications, nephropathy and retinopathy were available in a subset of diabetic patients. Association between genotype and insulin secretion/action was assessed in the additional sample of 335 individuals who underwent a hyperglycaemic clamp.

Principal Findings

We found that all the genotyped KCNQ1 variants were significantly associated with type 2 diabetes in our Dutch population, and the association of rs151290 was the strongest (OR 1.20, 95% CI 1.07–1.35, p = 0.002). The risk C-allele of rs151290 was nominally associated with reduced first-phase glucose-stimulated insulin secretion, while the non-risk T-allele of rs2237892 was significantly correlated with increased second-phase glucose-stimulated insulin secretion (p = 0.025 and 0.0016, respectively). In addition, the risk C-allele of rs2237892 was associated with higher LDL and total cholesterol levels (p = 0.015 and 0.003, respectively). We found no evidence for an association of KCNQ1 with diabetic complications.

Conclusions

Common variants in the KCNQ1 gene are associated with type 2 diabetes in a Dutch population, which can be explained at least in part by an effect on insulin secretion. Furthermore, our data suggest that KCNQ1 is also associated with lipid metabolism.     

Molecular connectedness between self and none self-sustainable populations of Chinese mitten crab (Eriocheir sinensis, H. Milne Edwards, 1853) with focus to the Swedish Lake Vänern and the Oder and Vistula River in Poland

The highly invasive Chinese mitten crabs (Eriocheir sinensis) was studied to reveal the genetic relationship between three none self-sustainable population within the Polish Oder and Vistula River and Lake V?nern in Sweden. Crabs from self-sustainable populations were collected from the Elbe River (Germany), San Francisco Bay (USA) and five Asian river estuaries. Both parsimony and maximum likelihood analysis of the nuclear ITS 1 and ITS 2 regions reveal a similar topological pattern. The mitochondrial cytochrome c oxidase subunit I (COI) sequence had too low resolution to be informative. The Oder River haplotypes showed high sequence similarities to both the Elbe population and/or the native spawning areas in China. The Vistula River showed haplotypic similarity to specimens from the Oder River in Poland or the Elbe River. Also high sequence similarities were observed to the specimens from the Swedish Lake V?nern indicating to an origin from the River Elbe. Minor changes in evolutionary interpretation exist depending on how gaps are treated and the analytic method. There is a complex movement involving back and forth transoceanic colonization of the Chinese mitten crab haplotypes. Invasion routes are discussed in relation to ship transfer routes and canal waterways.     

Modeled differences of coral life-history traits influence the refugium potential of a remote Caribbean reef

Coral Reefs - Remote populations can influence connectivity and may serve as refugia from climate change. We investigated two reef-building corals (Pseudodiploria strigosa and Orbicella franksi)...