Founder effects drive the genetic structure of passively dispersed aquatic invertebrates
Populations of passively dispersed organisms in continental aquatic habitats typically show high levels of neutral genetic differentiation despite their high dispersal capabilities. Several evolutionary factors, including founder events, local adaptation, and life cycle features such as high population growth rates and the presence of propagule banks, have been proposed to be responsible for this paradox. Here, we have modeled the colonization process to assess the impact of migration rate, population growth rate, population size, local adaptation and life-cycle features on the population genetic structure in these organisms. Our simulations show that the strongest effect on population structure are persistent founder effects, resulting from the interaction of a few population founders, high population growth rates, large population sizes and the presence of diapausing egg banks. In contrast, the role of local adaptation, genetic hitchhiking and migration is limited to small populations in these organisms. Our results indicate that local adaptation could have different impact on genetic structure in different groups of zooplankters.
Montero-Pau et al. (2018) Founder effects drive the genetic structure of passively dispersed aquatic invertebrates. PeerJ 6:e6094 https://doi.org/10.7717/peerj.6094
Four tyrosine residues of the rice immune receptor XA21 are not required for interaction with the co-receptor OsSERK2 or resistance to Xanthomonas oryzae pv. oryzae
Tyrosine phosphorylation has emerged as an important regulator of plasma membrane-localized immune receptors activity. Here, we investigate the role of tyrosine phosphorylation in the regulation of rice XANTHOMONAS RESISTANCE 21 (XA21)-mediated immunity. We demonstrate that the juxtamembrane and kinase domain of Escherichia coli–expressed XA21 (XA21JK) autophosphorylates on tyrosine residues. Directed mutagenesis of four out of the nine tyrosine residues in XA21JK reduced autophosphorylation. These sites include Tyr698 in the juxtamembrane domain, and Tyr786, Tyr907, and Tyr909 in the kinase domain. Rice plants expressing XA21-GFP fusion proteins or proteins with these tyrosine residues individually mutated to phenylalanine (XA21YF-GFP), which prevents phosphorylation at these sites, maintain resistance to Xanthomonas oryzae pv. oryzae. In contrast, plants expressing phosphomimetic XA21 variants with tyrosine mutated to aspartate (XA21YD-GFP) were susceptible. In vitro purified XA21JKY698F, XA21JKY907F, and XA21JKY909F variants are catalytically active, whereas activity was not detected in XA21JKY768F and the four XA21JKYD variants. We previously demonstrated that interaction of XA21 with the co-receptor OsSERK2 is critical for biological function. Four of the XA21JKYF variants maintain interaction with OsSERK2 as well as the XA21 binding (XB) proteins XB3 and XB15 in yeast, suggesting that these four tyrosine residues are not required for their interaction. Taken together, these results suggest that XA21 is capable of tyrosine autophosphorylation, but the identified tyrosine residues are not required for activation of XA21-mediated immunity or interaction with predicted XA21 signaling proteins.
Caddell et al. (2018) Four tyrosine residues of the rice immune receptor XA21 are not required for interaction with the co-receptor OsSERK2 or resistance to Xanthomonas oryzae pv. oryzae. PeerJ 6:e6074 https://doi.org/10.7717/peerj.6074
A tuber mustard AP2/ERF transcription factor gene, BjABR1, functioning in abscisic acid and abiotic stress responses, and evolutionary trajectory of the ABR1 homologous genes in Brassica species
The AP2/ERF superfamily of transcription factors is one of the largest transcription factor families in plants and plays an important role in plant development processes and stress responses. In this study, BjABR1, an AP2/ERF superfamily gene, from tuber mustard (Brassica juncea var. tumida Tsen et Lee), sharing high amino acid sequence similarity with the AtABR1 (Arabidopsis thaliana AP2-like abscisic acid repressor 1) gene, were performed functional research, and the ABR1 homologous genes in Brassica species were identified and performed phylogenetic analysis. The promoter sequence of BjABR1 contained many phytohormone- and stress-related cis-elements; ABA (abscisic acid) and abiotic stresses can induce BjABR1 expression in tuber mustard; overexpression of BjABR1 in Arabidopsis can alleviate plant sensitivity to ABA and salt and osmotic stresses, and the alleviation may be due to changes in stress/ABA-induced gene expression. These results indicated that BjABR1 functions in ABA and abiotic stress responses. By BLAST searches against the genome database of five Brassica species (three diploids, B. rapa, B. nigra, and B. oleracea, and two allotetraploid, B. juncea and B. napus) using the protein sequence of AtABR1, 3, 3, 3, 6, and 5 ABR1 homologous genes in B. nigra, B. rapa, B. oleracea, B. juncea, and B. napus were identified, respectively, and they shared high sequence similarity. By sequence analysis, annotation mistakes of the protein-coding regions of two ABR1 homologous genes, GSBRNA2T00134741001 and BjuB007684, were found and corrected. Then, the evolution analysis of these ABR1 homologous genes showed that the ancestor of the three diploid species had three ABR1 homologous genes and each diploid inherited all the three genes from their ancestor; then, allotetraploid B. juncea inherited all the six genes from B. rapa and B. nigra with no gene lost, while allotetraploid B. napus inherited all the three genes from B. oleracea and two genes from B. rapa with one gene lost, indicating that ABR1 homologous genes possessed greater hereditary conservation in Brassica species. The ABR1 homologous genes between B. rapa and B. oleracea shared much higher sequence similarity compared to that of B. nigra in diploid species, indicating that ABR1 homologous genes in B. nigra had experienced more rapid evolution, and B. rapa and B. oleracea may share closer relationship compared to B. nigra. Moreover, the spatial and temporal expression analysis of six ABR1 homologous genes of tuber mustard showed that they possessed different expression models. These results imply that ABR1 homologous genes are important to Brassica plants, and they may possess similar function in ABA and abiotic stress responses but play a role in different tissues and growing stages of plant. This study will provide the foundation to the functional research of ABR1 homologous genes in the Brassica species and help to reveal and understand the evolution mechanisms of Brassica species.
Xiang et al. (2018) A tuber mustard AP2/ERF transcription factor gene, BjABR1, functioning in abscisic acid and abiotic stress responses, and evolutionary trajectory of the ABR1 homologous genes in Brassica species. PeerJ 6:e6071 https://doi.org/10.7717/peerj.6071
Changes in intentional binding effect during a novel perceptual-motor task
Perceptual-motor learning describes the process of improving the smoothness and accuracy of movements. Intentional binding (IB) is a phenomenon whereby the length of time between performing a voluntary action and the production of a sensory outcome during perceptual-motor control is perceived as being shorter than the reality. How IB may change over the course of perceptual-motor learning, however, has not been explicitly investigated. Here, we developed a set of IB tasks during perceptual-motor learning. Participants were instructed to stop a circular moving object by key press when it reached the center of a target circle on the display screen. The distance between the center of the target circle and the center of the moving object was measured, and the error was used to approximate the perceptual-motor performance index. This task also included an additional exercise that was unrelated to the perceptual-motor task: after pressing the key, a sound was presented after a randomly chosen delay of 200, 500, or 700 ms and the participant had to estimate the delay interval. The difference between the estimated and actual delay was used as the IB value. A cluster analysis was then performed using the error values from the first and last task to group the participants based on their perceptual-motor performance. Participants showing a very small change in error value, and thus demonstrating a small effect of perceptual-motor learning, were classified into cluster 1. Those who exhibited a large decrease in error value from the first to the last set, and thus demonstrated a strong improvement in perceptual-motor performance, were classified into cluster 2. Those who exhibited perceptual-motor learning also showed improvements in the IB value. Our data suggest that IB is elevated when perceptual-motor learning occurs.
Morioka et al. (2018) Changes in intentional binding effect during a novel perceptual-motor task. PeerJ 6:e6066 https://doi.org/10.7717/peerj.6066
Combining ultraconserved elements and mtDNA data to uncover lineage diversity in a Mexican highland frog (Sarcohyla; Hylidae)
Molecular studies have uncovered significant diversity in the Mexican Highlands, leading to the description of many new endemic species. DNA approaches to this kind of species discovery have included both mitochondrial DNA (mtDNA) sequencing and multilocus genomic methods. While these marker types have often been pitted against one another, there are benefits to deploying them together, as linked mtDNA data can provide the bridge between uncovering lineages through rigorous multilocus genomic analysis and identifying lineages through comparison to existing mtDNA databases. Here, we apply one class of multilocus genomic marker, ultraconserved elements (UCEs), and linked mtDNA data to a species complex of frogs (Sarcohyla bistincta, Hylidae) found in the Mexican Highlands. We generated data from 1,891 UCEs, which contained 1,742 informative SNPs for S. bistincta and closely related species and captured mitochondrial genomes for most samples. Genetic analyses based on both whole loci and SNPs agree there are six to seven distinct lineages within what is currently described as S. bistincta. Phylogenies from UCEs and mtDNA mostly agreed in their topologies, and the few differences suggested a more complex evolutionary history of the mtDNA marker. Our study demonstrates that the Mexican Highlands still hold substantial undescribed diversity, making their conservation a particularly urgent goal. The Trans-Mexican Volcanic Range stands out as a significant geographic feature in Sarcohyla and may have acted as a dispersal corridor for S. bistincta to spread to the north. Combining multilocus genomic data with linked mtDNA data is a useful approach for identifying potential new species and associating them with already described taxa, which will be especially important in groups with undescribed subadult phenotypes and cryptic species.
Zarza et al. (2018) Combining ultraconserved elements and mtDNA data to uncover lineage diversity in a Mexican highland frog (Sarcohyla; Hylidae). PeerJ 6:e6045 https://doi.org/10.7717/peerj.6045
Effects of crude oil on survival and development in embryonated eggs in Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae)
Blue crabs, Callinectes sapidus Rathbun, 1896, are ubiquitous along the Atlantic and Gulf coasts of the USA. These organisms play an integral role in the ecosystems of the Gulf of Mexico (GOM), where not only are they a keystone species, but are also socioeconomically important. The survival of embryonated eggs is necessary to ensure adequate recruitment into the next generation. Because the 2010 Deepwater Horizon oil spill (DWH) occurred during the peak of the blue crab spawning season, the incident likely impacted blue crab embryos. In order to assess the effect of oil on embryonic growth and development, we collected embryonated eggs from seven different female blue crabs from the GOM throughout the spawning season and exposed them to an oil concentration of 500 ppb (the approximate concentration of oil at the surface water near the site of the Deepwater Horizon oil rig). Exposure to oil at this concentration caused a significantly larger proportion of prezoeae vs. zoeae to hatch from embryonated eggs in experiments lasting longer than 4 days. Exposure to oil did not significantly affect overall survival or development rate. The prezoeal stage is a little-studied stage of blue crab development. Though it may or may not be a normal stage of development, this stage has been found to occur in suboptimal conditions and has lower survival than zoeal stages. The larger proportion of prezoeae following prolonged exposure to oil thus indicates that crude oil at concentrations likely to be experienced by crabs after the DWH spill negatively impacted the development of blue crab embryos. In addition to providing insight into the effects of the DWH, this study sheds light on embryonic development in blue crabs, a critical, but poorly investigated phase of this important species’ life cycle.
Kelly et al. (2018) Effects of crude oil on survival and development in embryonated eggs in Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae). PeerJ 6:e5985 https://doi.org/10.7717/peerj.5985
Stress among on-duty firefighters: an ambulatory assessment study
Background Stress at work has been broadly acknowledged as a worldwide problem and has been the focus of concern for many researchers. Firefighting, in particular, is frequently reported as a highly stressful occupation. In order to investigate firefighters’ occupational health in terms of stress events, perceptions, symptoms, and physiological reactions under real-world conditions, an ambulatory assessment protocol was developed. Methods Seventeen firefighters’ cardiac signal was continuously monitored during an average of three shifts within a working week with medical clinically certified equipment (VitalJacket®), which allows for continuous electrocardiogram (ECG) and actigraphy measurement. Psychological data were collected with a software application running on smartphones, collecting potential stressful events, stress symptoms, and stress appraisal. Results A total of 450.56 h of medical-quality ECG were collected, and heart rate variability (HRV) analysis was performed. Findings suggest that although ‘fire’ situations are more common, ‘accidents’ are more stressful. Additionally, firefighters showed high levels of physiological stress (based on AVNN and LF/HF HRV metrics) when compared to normative healthy population values that may not be diagnosed using merely self-reports. Discussion The proposed ambulatory study seems to be useful for the monitoring of stress levels and its potential impact on health of first responders. Additionally, it could also be an important tool for the design and implementation of efficient interventions and informed management resolutions in real time. Potential applications of this research include the development of quantified occupational health (qOHealth) devices for real life monitoring of emergency personnel stress reactions.
Rodrigues et al. (2018) Stress among on-duty firefighters: an ambulatory assessment study. PeerJ 6:e5967 https://doi.org/10.7717/peerj.5967
Plant-derived chimeric antibodies inhibit the invasion of human fibroblasts by Toxoplasma gondii
The parasite Toxoplasma gondii causes an opportunistic infection, that is, particularly severe in immunocompromised patients, infants, and neonates. Current antiparasitic drugs are teratogenic and cause hypersensitivity-based toxic side effects especially during prolonged treatment. Furthermore, the recent emergence of drug-resistant toxoplasmosis has reduced the therapeutic impact of such drugs. In an effort to develop recombinant antibodies as a therapeutic alternative, a panel of affinity-matured, T. gondii tachyzoite-specific single-chain variable fragment (scFv) antibodies was selected by phage display and bioinformatic analysis. Further affinity optimization was attempted by introducing point mutations at hotspots within light chain complementarity-determining region 2. This strategy yielded four mutated scFv sequences and a parental scFv that were used to produce five mouse–human chimeric IgGs in Nicotiana benthamiana plants, with yields of 33–72 mg/kg of plant tissue. Immunological analysis confirmed the specific binding of these plant-derived antibodies to T. gondii tachyzoites, and in vitro efficacy was demonstrated by their ability to inhibit the invasion of human fibroblasts and impair parasite infectivity. These novel recombinant antibodies could therefore be suitable for the development of plant-derived immunotherapeutic interventions against toxoplasmosis.
Lim et al. (2018) Plant-derived chimeric antibodies inhibit the invasion of human fibroblasts by Toxoplasma gondii. PeerJ 6:e5780 https://doi.org/10.7717/peerj.5780
Behavior problems and personality in Korean high school students
Introduction Extant studies have examined the effect of psychological characteristics on clinical features that define behavior problems. The purpose of this study was to analyze the effects of temperament and character as both individual factors and complex profiles on behavior problems in a community sample of adolescents. Methods Behavior problems and personality of 670 Korean high school students were measured with the Youth Self-Report (YSR) and Junior version of the Temperament and Character Inventory (JTCI). Stepwise regression analysis analyzed the effects of JTCI character and temperament traits on YSR Total, Internalizing and Externalizing subscale scores, and Profile Analysis examined differences of JTCI personality profiles among three latent YSR subscale profiles acquired from Latent Profile Analysis. Results Seven subscales of the JTCI explained 38% of the YSR total degree of behavior problems, and JTCI Novelty-Seeking and Harm-Avoidance were found to account for vulnerability while JTCI Reward-Dependence and Self-Directedness explained resilience to behavior problems. There were three distinct latent YSR profile groups based on nine YSR subscales, and low behavior problem group showed a resilient personality profile characterized by low Novelty-Seeking and Harm-Avoidance and high Reward-Dependence, Persistence, Self-Directedness and Cooperativeness while high behavior problem group exhibited a vulnerable personality profile of the opposite tendency. Discussion Temperament and character explained behavior problems of Korean high school students as both individual personality traits and a complex personality profile. The results and implications of this study were examined in regard to mental health of adolescents, and the importance of education in the development of mature personality are discussed.
Lee et al. (2018) Behavior problems and personality in Korean high school students. PeerJ 6:e6106 https://doi.org/10.7717/peerj.6106
Effects of gelsemine on oxidative stress and DNA damage responses of Tetrahymena thermophila
Gelsemine is an important toxic substance extracted from Gelsemium elegans, which has a lot of biological functions in cells and organisms, but its toxicity has been rarely reported in Tetrahymena thermophila. In this study, we used the protozoan T. thermophila as an experimental model to investigate the potential toxicity-induced mechanism of gelsemine in the unicellular eukaryote. Our results clearly showed gelsemine inhibited T. thermophila growth in a dose-dependent manner. This exposure also resulted in oxidative stress on T. thermophila cells and antioxidant enzyme levels were significantly altered at high gelsemine levels (p < 0.05). Gelsemine produced a slight apoptotic effect at the highest (0.8 mg/mL) gelsemine level used here (p < 0.05). Furthermore, the toxin-induced DNA damage in a dose-dependent manner. The ultrastructural analysis also revealed mitophagic vacuoles at 0.4 and 0.8 mg/mL levels of gelsemine exposure. Moreover, expressions of oxidative stress-related and MAP kinase genes were significantly changed after exposure to 0.8 mg/mL level of gelsemine (p < 0.05). Altogether, our results clearly show that gelsemine from G. elegans can inhibit the growth via inducing oxidative stress and DNA damage in T. thermophila cells.
Ye et al. (2018) Effects of gelsemine on oxidative stress and DNA damage responses of Tetrahymena thermophila. PeerJ 6:e6093 https://doi.org/10.7717/peerj.6093