Heat shocks during egg incubation led to developmental,morphological, and behavioral differences in Arctic charr (Salvelinus alpinus)

Temperature variation is affecting fish biodiversity worldwide, causing changes in geographic distribution, phenotypic structure, and even species extinction. Incubation is a critical stage for stenothermic species, which are vulnerable to large temperature fluctuations, and its effects on the phenotype at later developmental stages are understudied, despite the fact that the phenotype being essential for organism ecology and evolution. In this study, we tested the effects of heat shocks during the embryonic period on the phenotype of Arctic charr (Salvelinus alpinus). We repeatedly quantified multiple phenotypic traits, including morphology, development, and behavior, over a period of 4 months, from hatching to juvenile stage in individuals that had experienced heat shocks (+ 5°C on 24 h, seven times) during their embryonic stage and those that had not. We found that heat shocks led to smaller body size at hatching and a lower sociability. Interestingly, these effects weakened throughout the development of individuals and even reversed in the case of body size. We also found an accelerated growth rate and a higher body condition in the presence of heat shocks. Our study provides evidence that heat shocks experienced during incubation can have long-lasting effects on an individual's phenotype. This highlights the importance of the incubation phase for the development of ectothermic organisms and suggests that temperature fluctuations may have significant ecological and evolutionary implications for Arctic charr. Given the predicted increase in extreme events and the unpredictability of temperature fluctuations, it is critical to further investigate their effects on development by examining fluctuations that vary in frequency and intensity.     

SARS-CoV-2 antibodies protect against reinfection for at least 6 months in a multicentre seroepidemiological workplace cohort

Identifying the potential for SARS-CoV-2 reinfection is crucial for understanding possible long-term epidemic dynamics. We analysed longitudinal PCR and serological testing data from a prospective cohort of 4,411 United States employees in 4 states between April 2020 and February 2021. We conducted a multivariable logistic regression investigating the association between baseline serological status and subsequent PCR test result in order to calculate an odds ratio for reinfection. We estimated an odds ratio for reinfection ranging from 0.14 (95% CI: 0.019 to 0.63) to 0.28 (95% CI: 0.05 to 1.1), implying that the presence of SARS-CoV-2 antibodies at baseline is associated with around 72% to 86% reduced odds of a subsequent PCR positive test based on our point estimates. This suggests that primary infection with SARS-CoV-2 provides protection against reinfection in the majority of individuals, at least over a 6-month time period. We also highlight 2 major sources of bias and uncertainty to be considered when estimating the relative risk of reinfection, confounders and the choice of baseline time point, and show how to account for both in reinfection analysis.

Identifying the potential for SARS-CoV-2 reinfection is crucial for understanding possible long-term epidemic dynamics. Analysis of a seroepidemiological cohort suggests that primary infection with SARS-CoV-2 protects against reinfection in the majority of individuals, at least over a six month period.     

Little Evidence to Support the Risk–Disturbance Hypothesis as an Explanation for Responses to Anthropogenic Noise by Pygmy Marmosets (Cebuella niveiventris) at a Tourism site in the Peruvian Amazon

The risk–disturbance hypothesis states that animals react to human stressors in the same way as they do to natural predators. Given increasing human–wildlife contact, understanding whether animals perceive anthropogenic sounds as a threat is important for assessing the long-term sustainability of wildlife tourism and proposing appropriate mitigation strategies. A study of pygmy marmoset (Cebuella niveiventris) responses to human speech found marmosets fled, decreased feeding and resting, and increased alert behaviors in response to human speech. Following this study, we investigated pygmy marmoset reactions to playbacks of different acoustic stimuli: controls (no playback, white noise and cicadas), anthropogenic noise (human speech and motorboats), and avian predators. For each playback condition, we recorded the behavior of a marmoset and looked at how the behaviors changed during and after the playback relative to behaviors before. We repeated this on ten different marmoset groups, playing each condition once to each group. The results did not replicate a previous study on the same species, at the same site, demonstrating the importance of replication in primate research, particularly when results are used to inform conservation policy. The results showed increased scanning during playbacks of the cicadas and predators compared with before the playback, and an increase in resting after playbacks of avian predators, but no evidence of behavior change in response to playbacks of human speech. There was no effect of ambient sound levels or distance between the playback source and focal animals on their behavior for all playback conditions. Although we find that noise can change the behavior of pygmy marmosets, we did not find evidence to support the risk–disturbance hypothesis.

     

Soil protist function varies with elevation in the Swiss Alps

Protists are abundant and play key trophic functions in soil. Documenting how their trophic contributions vary across large environmental gradients is essential to understand and predict how biogeochemical cycles will be impacted by global changes. Here, using amplicon sequencing of environmental DNA in open habitat soil from 161 locations spanning 2600 m of elevation in the Swiss Alps (from 400 to 3000 m), we found that, over the whole study area, soils are dominated by consumers, followed by parasites and phototrophs. In contrast, the proportion of these groups in local communities shows large variations in relation to elevation. While there is, on average, three times more consumers than parasites at low elevation (400–1000 m), this ratio increases to 12 at high elevation (2000–3000 m). This suggests that the decrease in protist host biomass and diversity toward mountains tops impact protist functional composition. Furthermore, the taxonomic composition of protists that infect animals was related to elevation while that of protists that infect plants or of protist consumers was related to soil pH. This study provides a first step to document and understand how soil protist functions vary along the elevational gradient.     

Analysis of a cDNA-derived sequence of a novel mannose-binding lectin, codakine, from the tropical clam Codakia orbicularis

This work relates to the characterisation of the predominant gill protein of the white clam, Codakia orbicularis (Linné, 1758), which harbours endosymbiotic sulphur-oxidising chemoautotrophic bacteria. Total RNA was extracted from the clam to perform 3'rapid amplification of cDNA ends (3'RACE) using degenerate oligonucleotides prepared from a partial sequence of a predominant protein of about 14kDa, termed codakine. The partial peptide sequence was obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and Edman degradation. Clones isolated from the cDNA library and containing the gene of interest were used in polymerase chain reaction (PCR). The PCR and RACE-PCR products were sequenced to determine the entire coding DNA sequence of codakine. BLAST analysis revealed about 23% to 29% sequence identity between codakine and various animal C-type lectins that are often involved in symbiosis and immune defences. Codakine also contains the motifs and domains of Ca(2+)-dependent C-type lectins, and in particular the tripeptide EPN motif frequently found in mannose-binding lectins (MBLs). Analysis of the protein by affinity chromatography on a mannose-agarose column is consistent with the findings that codakine is a dimeric Ca(2+)-dependent MBL of about 29kDa. Based on the present results, it is hypothesised that this novel C. orbicularis gill protein is involved in the recognition of symbiotic and pathogenic bacteria.     

Assessing the role of the active-site cysteine ligand in the superoxide reductase from Desulfoarculus baarsii

Superoxide reductase is a novel class of non-heme iron proteins that catalyzes the one-electron reduction of O(2)(.) to H(2)O(2), providing an antioxidant defense in some bacteria. Its active site consists of an unusual non-heme Fe(2+) center in a [His(4) Cys(1)] square pyramidal pentacoordination. In this class of enzyme, the cysteine axial ligand has been hypothesized to be an essential feature in the reactivity of the enzyme. Previous Fourier transform infrared spectroscopy studies on the enzyme from Desulfoarculus baarsii revealed that a protonated carboxylate group, proposed to be the side chain of Glu(114), is in interaction with the cysteine ligand. In this work, using pulse radiolysis, Fourier transform infrared, and resonance Raman spectroscopies, we have investigated to what extent the presence of this Glu(114) carboxylic lateral chain affects the strength of the S-Fe bond and the reaction of the iron active site with superoxide. The E114A mutant shows significantly modified pulse radiolysis kinetics for the protonation process of the first reaction intermediate. Resonance Raman spectroscopy demonstrates that the E114A mutation results in both a strengthening of the S-Fe bond and an increase in the extent of freeze-trapping of a Fe-peroxo species after treatment with H(2)O(2) by a specific strengthening of the Fe-O bond. A fine tuning of the strength of the S-Fe bond by the presence of Glu(114) appears to be an essential factor for both the strength of the Fe-O bond and the pK(a) value of the Fe(3+)-peroxo intermediate species to form the reaction product H(2)O(2).     

Kinetic and mutational analyses of the major cytosolic exopolyphosphatase from Saccharomyces cerevisiae

Yeast exopolyphosphatase (scPPX) processively splits off the terminal phosphate group from linear polyphosphates longer than pyrophosphate. scPPX belongs to the DHH phosphoesterase superfamily and is evolutionarily close to the well characterized family II pyrophosphatase (PPase). Here, we used steady-state kinetic and binding measurements to elucidate the metal cofactor requirement for scPPX catalysis over the pH range 4.2-9.5. A single tight binding site for Mg(2+) (K(d) of 24 microm) was detected by equilibrium dialysis. Steady-state kinetic analysis of tripolyphosphate hydrolysis revealed a second site that binds Mg(2+) in the millimolar range and modulates substrate binding. This step requires two protonated and two deprotonated enzyme groups with pK(a) values of 5.0-5.3 and 7.6-8.2, respectively. The catalytic step requiring two deprotonated groups (pK(a) of 4.6 and 5.6) is modulated by ionization of a third group (pK(a) of 8.7). Conservative mutations of Asp(127), His(148), His(149) (conserved in scPPX and PPase), and Asn(35) (His in PPase) reduced activity by a factor of 600-5000. N35H and D127E substitutions reduced the Mg(2+) affinity of the tight binding site by 25-60-fold. Contrary to expectations, the N35H variant was unable to hydrolyze pyrophosphate, but markedly altered metal cofactor specificity, displaying higher catalytic activity with Co(2+) bound to the weak binding site versus the Mg(2+)- or Mn(2+)-bound enzyme. These results provide an initial step toward understanding the dynamics of scPPX catalysis and reveal significant functional differences between structurally similar scPPX and family II PPase.     

The role of p63 in germ cell apoptosis in the developing testis

The fetal and neonatal development of male germ cells (gonocytes) is a poorly understood but crucial process for establishing fertility. In rodents, gonocytes go through two phases of proliferation accompanied by apoptosis and separated by a quiescent period during the end of fetal development. P63 is a member of the P53 gene family that yields six isoforms. We detected only the p63 protein and no p53 and p73 in the nucleus of the gonocytes of mouse testes. We report for the first time the ontogeny of each p63 mRNA isoform during testis development. We observed a strong expression of p63gamma mRNA and protein when gonocytes are in the quiescent period. In vitro treatment with retinoic acid prevented gonocytes from entering the quiescent period and was correlated with a reduced production of p63gamma isoform mRNA. We investigated the function of p63 by studying the testicular phenotype of P63-null mice. P63 invalidation slightly, but significantly increased the number of gonocytes counted during the quiescent period. As P63-null animals die at birth we used an original organ culture that mimicked neonatal in vivo development to study further the testicular development. P63 invalidation resulted in a sharply increased number of gonocytes during the culture period due to a decrease in spontaneous apoptosis with no change in proliferation. P63 invalidation also caused abnormal morphologies in the germ cells that were also found in P63(+/-) adult male mice. Thus, p63 appears as an important regulator of germ cell development.     

Role of STAT3 in CD4+CD25+FOXP3+ regulatory lymphocyte generation: implications in graft-versus-host disease and antitumor immunity

Immunological tolerance is maintained by specialized subsets of T cells including CD4(+)CD25(+)FOXP3(+) regulatory cells (Treg). Previous studies established that Treg thymic differentiation or peripheral conversion depend on CD28 and Lck signaling. Moreover, foxp3 gene transfer in murine CD4(+)CD25(-) T lymphocytes results in the acquisition of suppressive functions. However, molecular pathways leading to FOXP3 expression remain to be described. In this study, we investigated the molecular events driving FOXP3 expression. We demonstrated that CD28 activation in CD4(+)CD25(-) T lymphocytes leads to STAT3 Tyr(705) phosphorylation in an Lck-dependent manner. STAT3 neutralization during naive peripheral CD4(+)CD25(-) T cell conversion into Treg through costimulation with TCR/CD28 and TGF-beta1, decreased FOXP3 expression, prevented the acquisition of suppressive functions and restored the ability of the converted lymphocytes to produce IL-2 and IFN-gamma. Furthermore, we observed that STAT3 ablation using small interfering RNA strategies inhibited FOXP3 expression and suppressive functions among naturally differentiated CD4(+)CD25(+) T lymphocytes, suggesting a direct role of STAT3 in Treg phenotype and function maintenance. CD4(+)CD25(+) T lymphocytes transduced with specific STAT3 small interfering RNA were devoid of suppressive functions and failed to control the occurrence of acute graft-vs-host disease. Finally, STAT3 inhibition in CD4(+) lymphocytes enhanced the anti-tumor immunity conferred by a lymphocyte adoptive transfer. In summary, our findings determine that STAT3 is critical in the molecular pathway required for FOXP3 expression. STAT3 modulation should be taken into account when assessing how regulatory T cells contribute to inflammatory diseases and tumor immunosurveillance.