Search Results (471)

The transport mechanisms for substrates and nutrients within the heme pathway of the Toxoplasma gondii apicoplast remain poorly understood. However, studies on heme metabolic enzymes have employed disparate genetic manipulation approaches, limiting direct phenotypic comparisons among different enzymes. This research involved screening potential apicoplast proteins in Toxoplasma gondii by cross-referencing and analyzing protein–protein interaction networks. Within the heme enzyme pathway of the apicoplast, eight enzymes were found to be predominantly conserved in the Sarcocystide family. Utilizing the CRISPR-Cas9 system alongside a U1 snRNP-mediated gene-silencing approach, we developed inducible knockdown strains—iKD-PBGD, iKD-UROS, and iKD-UROD—targeting three key metabolic enzymes crucial for the parasite lytic cycle, as demonstrated through replication experiments. To investigate the transport mechanisms for heme-related nutrients or substrates, we knocked down these three enzymes, using TgGRA12 as an initial marker. Continuous fluorescence signals highlighted the parasitophorous vacuole (PV) membrane surrounding tachyzoites during both early and late replication stages, particularly at 48 h post-rapamycin treatment, indicating a transformation of the cyst-like PV resembling that in Toxoplasma gondii. Phenotypically, knockdown of these heme enzymes led to the formation of slowly replicating, cyst-like parasitophorous vacuoles. However, this morphological change did not significantly affect the acute virulence of the parasites in vivo, as determined by mouse survival assays. This study explored the functional roles of the three intermediate metabolic enzymes, offering a novel viewpoint on the gradual demise of Toxoplasma gondii as a potential target for drug development. Full article

Eukaryotic cells rely on a highly coordinated organelle network to maintain metabolism, signaling, stress adaptation and cell survival. Membrane contact sites (MCSs) provide essential platforms for inter-organelle communication. As obligate intracellular parasites, less attention has been given to how viral perturbation of MCSs may reshape the broader organelle communication network. In this review, we focus on positive-sense RNA viruses and virus-induced membrane contact sites (vMCSs), focusing on ER-associated tethering factors, lipid transfer pathways, calcium signaling modules, and replication organelle–host organelle interfaces. Also we discuss how viruses hijack conserved host tethering systems to connect viral replication compartments with lipid transfer machinery. Further, we explore how viruses establish vMCSs that couple replication compartments to host organelles, thereby coordinating cellular homeostasis. Together, these findings suggest that viral remodeling of MCSs should be understood not only as local manipulation of individual organelles but also as a network-level reorganization of cellular homeostasis. Full article

The major histocompatibility complex (MHC) represents a critical genetic locus that orchestrates adaptive immune responses through antigen presentation and T cell activation, characterized by exceptional polymorphism and species-specific diversity. In herbivores, MHC polymorphisms constitute fundamental determinants of resistance to parasitic, viral, and bacterial infections while serving as crucial indicators of genetic diversity and breeding value in animal populations. Recent advances in high-throughput sequencing technologies, single-cell omics, and population genetics have substantially advanced understanding of MHC gene structure, allelic polymorphism, evolutionary patterns, and associations with disease susceptibility and vaccine responsiveness. This comprehensive review systematically examines the structural characteristics and regulatory mechanisms of MHC genes, their associations with infectious disease resistance, their role in vaccine responses, and their practical applications in molecular breeding programs, conservation genetics, and immunological research. We identify current technical limitations and outline future research directions to establish a robust theoretical foundation for disease resistance breeding and immune regulation strategies in herbivore populations. Full article

Biological control using parasitoids is a key strategy for managing psyllid pests in horticultural crops. This study investigated the parasitoid complex associated with Bactericera tremblayi and Bactericera trigonica, two economically important psyllid pests of leek and carrot, respectively, in Castile and León (Spain). Nymphs of both psyllid species were collected and reared to assess parasitism; emerging parasitoids were identified morphologically and by DNA barcoding. A total of 969 parasitized nymphs were collected, from which 291 parasitoids emerged, including Tamarixia pronomus, Tamarixia tremblayi, Syrphophagus herbidus, Syrphophagus cf. taeniatus, Cheiloneurus sp. and Encyrtidae sp. Tamarixia pronomus is reported here for the first time as parasitoids of B. tremblayi while T. tremblayi, S. herbidus, and S. cf. taeniatus are newly recorded as parasitoids of B. trigonica. Moreover, the two Syrphophagus species represent the first records of this genus for Spain. The COI barcode sequences were generated for T. pronomus, T. tremblayi and S. cf. taeniatus. The parasitism rate of S. herbidus on B. trigonica reached a maximum of 23.18%. No significant differences in parasitism by Tamarixia species were observed between the two Bactericera hosts. Maximum parasitism rates recorded were 32.43% for T. pronomus on B. trigonica, and approximately 11–12% for T. tremblayi on both host species. Total parasitism of B. tremblayi in leek crops reached up to 70%, whereas parasitism of B. trigonica in carrot remained generally low and poorly synchronized with pest population dynamics. These results highlight a diverse parasitoid complex with substantial natural control of B. tremblayi and variable but lower impact on B. trigonica, underscoring the relevance of habitat and temporal factors for conservation biological control in these agroecosystems. Full article

Fungi have evolved sophisticated mechanisms to survive in complex environments. Nematode-trapping fungi (NTF) sense and recognize nematode prey to transition from a saprophytic to predatory lifestyle, rendering them promising biocontrol agents against plant-parasitic nematodes. Ubiquitination is essential for eukaryotic cellular homeostasis, yet its regulation of NTF development and pathogenicity remains unclear. Here, we identify the conserved E3 ubiquitin ligase AoRsp5 as a critical factor for all major life stages of Arthrobotrys oligospora. Knockout of rsp5 impairs Endosomal Sorting Complex Required for Transport (ESCRT)-mediated endocytosis and compromises plasma membrane integrity. These defects trigger disturbed cellular iron homeostasis and ferroptosis-like cell death, accompanied by global dysregulation of protein phosphorylation and ubiquitination as well as prominent suppression of MAPK cascades, which further attenuate virulence-associated signaling. Overall, our findings reveal a pivotal role for Rsp5-mediated ubiquitination in coordinating cellular homeostasis and developmental transitions in NTF. Full article

Visceral leishmaniasis, caused by Leishmania donovani, is characterized by profound alterations in hepatic immune responses that promote parasite persistence. However, the lack of physiologically relevant in vitro systems limits investigation of tissue-level host–pathogen interactions. An immunocompetent three-dimensional hepatic organoid model incorporating bone marrow-derived macrophages was established to investigate liver-stage immune responses to L. donovani infection. Integrated cytokine profiling and transcriptomic analyses were benchmarked against infected mouse liver tissue. Macrophages acquired functional characteristics consistent with a Kupffer cell-like phenotype and contributed to immune homeostasis within the co-culture. Infection induced a conserved immune response characterized by inflammatory and chemotactic activation. This response was accompanied by coordinated suppression of antimicrobial pathways, including the IL-12–IFN-γ axis and interferon-stimulated genes. These immune alterations were largely shared between the organoid model and infected liver tissue, although systemic metabolic reprogramming and multicellular complexity were not fully recapitulated. Our findings identify a conserved pattern of hepatic immune dysregulation in which inflammatory activation is uncoupled from effective antimicrobial signaling, potentially facilitating parasite persistence. This immunocompetent hepatic organoid platform provides a physiologically relevant system for investigating host–pathogen interactions and evaluating host-directed therapeutic strategies for visceral leishmaniasis. Full article

The Oriental stork, Ciconia boyciana Swinhoe, 1873 (Ciconiiformes: Ciconiidae), once common as a sedentary stork species across Japan, experienced a marked population decline during the last century, reaching extinction in the country in 1971 as a result of anthropogenic alterations to the natural environment. After the reintroduction of five captive descendants of continental pairs in 2005, the naturalized population of Oriental storks has steadily increased in Japan, reaching >500 wild storks by 2025. We recently encountered a case of apparent intestinal fluke infection with Chaunocephalus ferox (Echinostomata; Echinostomatidae) in a 2-month-old stork fledgling within a few days after leaving the nest on 29 June 2025. The parasite was subjected to morphological and molecular identification based on nucleotide sequences of the small- to large-subunit ribosomal RNA gene and mitochondrial cytochrome c oxidase subunit 1 gene and was identified as C. ferox, a parasite exhibiting high host specificity for ciconiid birds worldwide. This finding suggests the re-establishment of its natural transmission cycle in the field in Japan, accompanied by the dispersal of definitive hosts after a gap of at least 30 years. Following the establishment of a reintroduced sedentary Oriental stork population in Japan, this health-threatening chaunocephalosis may, by chance, have a pronounced impact on infection-susceptible stork chicks cared for and fed by parent birds inhabiting fields with dense C. ferox endemicity (hotspots). Another Oriental stork fledgling from the same nest in June 2025 survived and was observed in March 2026 in a paddy field at a distant locality. Parasites are natural components of healthy ecosystems that contribute to biodiversity and trophic balance; therefore, inappropriate anthropogenic habitat modification may create scenarios in which parasites become overly destructive rather than serving merely as ecological regulators. Full article

The Ponto-Danubian Basin Acipenseridae family includes species of fish with high economic value, as well as some of the most vulnerable taxonomic groups in terms of biodiversity conservation worldwide. Viral diseases have been documented considerably less frequently than bacterial and parasitic diseases. However, the European sturgeon iridovirus (AcIV-E) and herpes viruses have recently emerged as epizootic pathogens, raising concerns about their potential impact on sturgeon populations in the Black Sea basin. Bacterial pathogens were the main cause of the diseases reported in the reviewed literature. Many of these pathogens belonged to the Genera Aeromonas, Vibrio, Pseudomonas, and Citrobacter. These pathogens were particularly implicated in the etiology of septicemic and hemorrhagic symptoms, which significantly impacted the mortality of affected populations. Ecto- and endoparasitic infestations were primarily caused by protozoa, monogeneans, trematodes, and nematodes, resulting in tissue lesions of varying severity, depending on the parasite and the host’s immune status. Temporal analysis revealed a significant increase in reports of bacterial diseases after 2000, coinciding with the growth of sturgeon aquaculture in Turkey and Romania. Outbreaks of disease exhibited pronounced geographical clustering in the northwestern Black Sea Region and the Danube River. These areas are characterized by intensive aquaculture activity and ecological vulnerability. These findings highlight the importance of coordinated regional surveillance, wider adoption of molecular diagnostics, and incorporation of health management strategies into conservation planning for Acipenseridae populations in the Black Sea Region. Full article

(1) Background: Giardia duodenalis is a common protozoan parasite infecting various mammalian hosts, yet data on its prevalence in Cypriot ruminants, including the endemic and protected mouflon (Ovis gmelini ophion), remain absent. This study aimed to evaluate the prevalence and molecular characteristics of Giardia species (sp.) in domestic and wild ruminants in Cyprus to assess potential risks to wildlife. (2) Methods: We analysed 146 faecal samples—comprising 32 domestic sheep, 10 domestic and 34 free-ranging goats, and 70 wild mouflons—using nested polymerase chain reaction (PCR) and multi-locus sequence typing of the ssrRNA, tpi, bg, and gdh genes. (3) Results: Giardia was detected in only 1 of the 42 domestic ruminant samples (1/32 sheep; 3.1%), which was characterized as G. duodenalis assemblage E. No Giardia DNA was detected in the the domestic goats (0/10), wild mouflons (0/70) or the free-ranging goats (0/34) co-inhabiting the forest environment. (4) Conclusions: This study provides the first molecular report of Giardia sp. in domestic sheep in the Republic of Cyprus. While the parasite is present in domestic ruminants, the findings suggest a low positivity rate and no immediate evidence of transmission to the endangered mouflon. Further research with a larger sample size is recommended to confirm these observations and guide future conservation strategies. Full article

Cryptosporidium parvum is an important apicomplexan parasite that causes severe diarrheal disease in children and immunocompromised individuals. However, the structural basis for the limited immunogenicity of its T-cell epitopes remains poorly understood. This study integrates structural biology and immunological approaches to elucidate the molecular basis underlying the non-immunogenicity of KAV9, a Cp23-derived epitope with the sequence KAVKNPAPI. Biophysical analyses demonstrated that KAV9 forms a high-affinity complex with H-2D^b, with an IC₅₀ of 7.83 nM, and exhibits higher thermal stability (T_m = 59.16 °C) than the immunodominant LCMV gp33 epitope (T_m = 51.15 °C). Despite strong pMHC binding and high pMHC stability, in vivo peptide immunization failed to elicit a detectable KAV9-specific CD8⁺ T-cell response. Crystal structure analysis revealed that KAV9 is tightly accommodated within the H-2D^b binding groove through an extensive hydrogen-bond network. However, its distinct peptide conformation, particularly involving P4-Lys and the proline residues at P6 and P8, markedly reshapes the TCR-exposed surface compared to gp33. AlphaFold3 (AF3) modeling further suggested that these structural deviations disrupt critical hydrogen-bond interactions with the T-cell receptor (TCR) CDR3 loops, thereby eliminating contacts required for TCRβ engagement. Sequence analysis revealed that KAV9 is highly conserved across multiple Cryptosporidium species, suggesting a conserved structural feature associated with limited T-cell recognition. Together, these findings demonstrate that strong MHC binding and pMHC stability are insufficient to ensure CD8⁺ T-cell immunogenicity. Instead, the topology of the TCR-accessible peptide surface represents a critical determinant of epitope immunogenicity, with significant implications for epitope selection and vaccine design against cryptosporidiosis. Full article

A chimeric protein produced from the fusion of a type-P4 ATPase, also called flippase, and a guanylate cyclase (P4GC) was originally described in ciliates and malaria parasites. An extensive search for P4GC homologs was carried out, and the protein’s structural features were determined by sequence alignments and homology modeling. P4GC is found in all alveolate lineages and in some stramenopile lineages. This suggests that the gene fusion event occurred in a common ancestor of stramenopiles and alveolates after the divergence of rhizarians, although alternative evolutionary scenarios cannot be excluded. This scenario necessitates the subsequent loss of P4GC in some stramenopile lineages. Alternatively, the gene fusion may have arisen in an early alveolate lineage and subsequently been transferred horizontally to an ancestor of oomycetes and bicosoecids, or vice versa. The sequence homology of the flippase module is not well preserved in some lineages, whereas the structure and sequence homology of the cyclase module is highly conserved in all lineages. These findings suggest that the cyclase module has been subject to stronger evolutionary constraints than the flippase module, while the latter may have undergone lineage-specific functional diversification. However, despite sequence divergence, homology modeling indicates that the predicted 3-dimensional structures of the flippase modules are highly conserved across all lineages, suggesting that structural constraints have preserved its functional role(s) within P4GC. Together, these findings indicate that P4GC has undergone lineage-specific functional diversification while maintaining a highly conserved guanylate cyclase module throughout alveolate and stramenopile evolution. Full article

This study evaluated the short-term response of the fecal microbiota of wild Cavia tschudii during its transition from natural conditions to captivity under a standardized alfalfa-based diet. Fecal samples were collected over a 21-day period and analyzed using 16S rRNA gene sequencing to assess microbial diversity, community structure, and taxonomic composition. Rarefaction analysis indicated sufficient sequencing coverage; however, samples were normalized to 500 reads per sample, and results should be interpreted cautiously. No significant changes were detected in alpha diversity, beta diversity, or dominant taxonomic composition across sampling time points. The microbiota was consistently dominated by Bacteroidota and Firmicutes, accounting for more than 85% of total relative abundance. Minor taxa such as Methanobacteriales and Spirochaetales were present at low and stable abundances. Despite differences between natural forage and the alfalfa-based diet, microbial community structure showed limited temporal variation during the study period. The absence of detectable parasitic infections further supports that observed patterns reflect host–microbiota dynamics under controlled conditions. Functional predictions suggested variation in metabolic pathways but should be interpreted cautiously due to the limitations of 16S rRNA-based inference. Overall, these findings suggest limited temporal variation in the fecal microbiota of Cavia tschudii during the first three weeks of captivity under the conditions evaluated. However, due to the exploratory nature of the study and its methodological limitations, these results should be interpreted with caution. This study provides baseline insights into limited temporal variation in the fecal microbiota of a wild caviid species and contributes to understanding host–microbiome interactions relevant to conservation and potential domestication processes. Full article

Insect natural enemies are central agents in biological-control programs. Their pest-suppression performance depends not only on release strategy, but also on traits shaped by long-term laboratory rearing and selection. Conventional mass-rearing systems usually evaluate insect natural enemies using production-oriented indicators, such as survival, fecundity, emergence rate, sex ratio and production cost. However, continuous mass rearing can drive laboratory adaptation, genetic drift, inbreeding, shifts in host or prey use, and reduced field performance. In this review, we summarize key target traits for insect natural enemy improvement, including production efficiency, host or prey use, parasitism, predation, nonreproductive host killing, stress tolerance, pesticide compatibility, dispersal, retention and field efficacy. We further discuss how recurrent artificial selection, hybridization, population genetics, and genomics approaches can be integrated to improve insect natural enemies while maintaining genetic quality. Finally, we discuss the links among trait screening, selection design, quality control, storage and transport, and field-performance validation in the development and application of selected lines or improved strains. Overall, this review highlights practical directions for developing stable and field-proven natural enemy lines. Beyond agriculture, this perspective may also support ecological design in urban landscapes through natural enemy conservation and reduced pesticide use. Full article

The main purpose of this study is to overcome the difficulty of maintaining high-quality zero-voltage switching (ZVS) in resonant converters over wide operating ranges. Conservative designs ensuring light-load ZVS inevitably generate excessive reactive current, causing severe circulating losses and body diode conduction under heavy loads. To resolve this intrinsic trade-off, this paper proposes an active closed-loop optimal ZVS control strategy utilizing a DC-biased variable resonant inductor. The core mechanism actively shifts the tank impedance to dynamically reshape the primary current. By integrating the primary current during each dead time, the real-time integrated charge is actively regulated to track an optimal reference limit defined by the switch parasitic capacitance and dc-bus voltage. Consequently, the variable inductor continuously regulates the tank current toward the optimal ZVS boundary, ensuring the parasitic capacitance is completely discharged just before the turn-on instant. Validations via simulation and a 192 W hardware prototype confirm the method’s efficacy. The strategy completely eliminates light-load hard switching and significantly suppresses heavy-load body diode conduction without compromising output voltage regulation. Compared to conventional active schemes, this approach achieves full-range optimal ZVS without requiring additional high-frequency switching devices, establishing a highly efficient shift from passive parameter design to active boundary tracking. Full article

Successful conservation biological control programs require a good understanding the nutritional ecology of natural enemies to maximize their field efficacy. This study evaluated the effects of non-floral sugar sources on fitness parameters of Mastrus ridens, a specialized parasitoid of the codling moth. In the laboratory, we compared the longevity, parasitism, and reproduction of adult parasitoids exposed to different sugar sources, including Vicia faba extrafloral nectar, honeydew from several hemipteran species, diluted honey (positive control), and no-sugar controls. We also tested the effects of exposing parasitoids to honey for only 24 h. The results showed that sugar availability and source type significantly affected parasitoid performance. Extrafloral nectar was better than mealybug honeydew, with female offspring numbers similar to those exposed to honey, and increased the number of parasitized host larvae by up to 3.5-fold compared to no-sugar conditions. The effects of honeydew effects on male longevity were variable, possibly explained by its composition, and the mode of presentation. Parasitoids with a short exposure to high-quality sugar performed poorly. Our findings indicate that successful conservation and augmentative biological control programs using this species require field provision of high-quality, accessible sugar resources. Full article