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The apicoplast is a four-membrane plastid found in the apicomplexans, which harbors biosynthesis and organelle housekeeping activities in the matrix. However, the mechanism driving the flux of metabolites, in and out, remains unknown. Here, we used TurboID and genome engineering to identify apicoplast transporters in Toxoplasma gondii. Among the many novel transporters, we show that one pair of apicomplexan monocarboxylate transporters (AMTs) appears to have evolved from a putative host cell that engulfed a red alga. Protein depletion showed that AMT1 and AMT2 are critical for parasite growth. Metabolite analyses supported the notion that AMT1 and AMT2 are associated with biosynthesis of isoprenoids and fatty acids. However, stronger phenotypic defects were observed for AMT2, including in the inability to establish T. gondii parasite virulence in mice. This study clarifies, significantly, the mystery of apicoplast transporter composition and reveals the importance of the pair of AMTs in maintaining the apicoplast activity in apicomplexans.

The apicoplast is a four-membrane plastid found in the apicomplexans, which harbors biosynthesis and organelle housekeeping activities in the matrix. However, the mechanism driving the flux of metabolites, in and out, remains unknown. Here, we used TurboID and genome engineering to identify apicoplast transporters in Toxoplasma gondii . Among the many novel transporters, we show that one pair of apicomplexan monocarboxylate transporters (AMTs) appears to have evolved from a putative host cell that engulfed a red alga. Protein depletion showed that AMT1 and AMT2 are critical for parasite growth. Metabolite analyses supported the notion that AMT1 and AMT2 are associated with biosynthesis of isoprenoids and fatty acids. However, stronger phenotypic defects were observed for AMT2, including in the inability to establish T. gondii parasite virulence in mice. This study clarifies, significantly, the mystery of apicoplast transporter composition and reveals the importance of the pair of AMTs in maintaining the apicoplast activity in apicomplexans., Competing Interests: HD, JY, KH, WZ, DL, JL, HD, RW, KB, GH, ZL, XZ, SL No competing interests declared, (© 2023, Dong, Yang, He et al.)

The success of biological control may depend on the control agent co-evolving with its target pest species, precluding the emergence of resistance that often undermines chemical control. However, recent evidence of a decline in attack rates of a sexual pest weevil by its asexual parasitoid suggests that evolutionary arms races may not prevent the emergence of resistance if the host and parasitoid do not have reproductive strategies that generate equal amounts of genetic variation. To understand how these asymmetries in reproductive strategies may drive the emergence of resistance, we combined life history data from two pest weevils and their parasitoids (one sexual and one asexual) in the New Zealand pastoral ecosystem, with a population dynamic model that allows the coevolution of hosts and parasitoids. We found that the ratio of the genetic variance of hosts to parasitoids was a key determinant of the emergence of resistance. Host resistance eventually occurred unless the parasitoids had considerably greater additive genetic variance than their host. The higher reproductive rate of asexual parasitoids did little to offset the cost of reduced additive genetic variance. The model predictions were congruent with long-term parasitism rates observed in the field for both of the pests considered (one with a sexual and one with an asexual parasitoid). We then explored the consequences of introducing two parasitoids with different reproductive strategies that attack the same sexual host. The model showed that the sexually reproducing parasitoid always out-competed the asexually reproducing one. Our study shows that any asymmetry in reproductive strategies is extremely important for predicting the long-term success of biological control agents. Fortunately, introduction of sexually reproducing individuals after an initial introduction of asexual strains may overcome the problems of host resistance. We conclude that evolution must be considered when evaluating the long-term outcomes of importation biological control. [ABSTRACT FROM AUTHOR]

Nematode parasites rely on successful host infection to perpetuate their species. Infection by individual nematode parasites can be risky, however; any one individual could be killed by the host’s immune response. Here we use a model system to show that environmental cues and parasite past experience can be used by entomopathogenic nematodes to reduce individual risk of infection. Past parasite experience can more than double the infective virulence (number of host invaders) of a given cohort of entomopathogenic nematode parasites. This plasticity in individual parasite risk-taking and associated infection can be used to manage infection of parasitic nematodes: enhancing biological control with entomopathogenic nematodes and developing behavioral and chemical strategies to reduce infection by vertebrate and plant parasitic nematodes. [ABSTRACT FROM AUTHOR]

The parasitic insect Xenos vesparum induces noticeable behavioral and physiological changes—e.g. castration—in its female host, the paper wasp Polistes dominula: parasitized putative workers avoid any colony task and desert the colony to survive in the nearby vegetation, like future queens and males do. In this long-term observational study, we describe the spectacular attraction of parasitized workers towards trumpet creeper bushes (Campsis radicans) in early-summer. Two thirds of all wasps that we sampled on these bushes were parasitized, whereas the parasite prevalence was much lower in our study area and most wasps sampled on other nearby flowering bushes were non-parasitized. First, we describe the occurrence and consistency of this phenomenon across different sites and years. Second, we evaluate the spatial behavior of parasitized wasps on C. radicans bushes, which includes site-fidelity, exploitation and defense of rich extra-floral nectaries on buds and calices. Third, we record two critical steps of the lifecycle of X. vesparum on C. radicans: the parasite’s mating and a summer release of parasitic larvae, that can infect larval stages of the host if transported to the host’s nest. In a nutshell, C. radicans bushes provide many benefits both to the parasite X. vesparum and to its host: they facilitate the parasite’s mating and bivoltine lifecycle, a phenomenon never described before for this parasite, while, at the same time, they provide the wasp host with shelter inside trumpet flowers and extrafloral gland secretions, thus likely enhancing host survival and making it a suitable vector for the infection. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of sex, breeding center and age on fecal triiodothyronine levels in captive forest musk deer Moschus berezovskii, and to explore the age-intensity model of gastrointestinal parasites. Furthermore, the association between fecal triiodothyronine levels and parasite egg shedding was also analyzed. We collected musk deer fecal samples from two breeding centers located in Shaanxi and Sichuan province, China. Enzyme-linked immunosorbent assays were utilized to estimate the fecal triiodothyronine concentrations and profiles, and fecal parasite eggs or oocysts were counted using the McMaster technique. Female deer from both breeding centers consistently showed higher triiodothyronine concentrations than those observed in males, which indicates that a distinct physiology pattern occurs by sex. The triiodothyronine concentration in Sichuan breeding center was significantly higher than that in Shaanxi center for both sexes, suggesting that differences in environment, diet and management practices are likely to affect the metabolism. In addition, a negative relationship between triiodothyronine concentrations and age was found (r = - 0.75, p < 0.001), and parasite egg shedding was also negatively associated with age (r = - 0.51, p < 0.001), by which we can infer that older animals evolves a more developed immune system. Finally, a positive association between parasite egg shedding and triiodothyronine levels was found, which could be explained by the additional energy metabolism resulting from parasitic infection. Results from this study might suggest metabolic and immunological adaptations in forest musk deer. These baseline data could be used to unveil metabolic status and establish parasite control strategies, which has great potential in captive population management as well as their general health evaluations. [ABSTRACT FROM AUTHOR]

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Parasites are known to have direct negative effects on host fitness; however, the indirect effects of parasitism on host fitness sans infection are less well understood. Hosts undergo behavioural and physiological changes when in proximity to parasites. Yet, there is little experimental evidence showing that these changes lead to long-term decreases in host fitness. We aimed to determine if parasite exposure affects host fitness independent of contact, because current approaches to parasite ecology may underestimate the effect of parasites on host populations. We assayed the longevity and reproductive output of Drosophila nigrospiracula exposed or not exposed to ectoparasitic Macrocheles subbadius. In order to preclude contact and infection, mites and flies were permanently separated with a mesh screen. Exposed flies had shorter lives and lower fecundity relative to unexposed flies. Recent work in parasite ecology has argued that parasite–host systems show similar processes as predator–prey systems. Our findings mirror the non-consumptive effects observed in predator–prey systems, in which prey species suffer reduced fitness even if they never come into direct contact with predators. Our results support the perspective that there are analogous effects in parasite–host systems, and suggest new directions for research in both parasite ecology and the ecology of fear. [ABSTRACT FROM AUTHOR]

Single-cell RNA sequencing (scRNAseq) technologies are changing the way we study populations of cells by allowing for an unbiased characterization of the composition of these populations. This Forum article highlights outstanding questions in parasitology that could benefit from scRNAseq and provides guiding thoughts for planning such experiments. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii is an intracellular protozoan parasite widely distributed in animals and humans. Infection of host cells and parasite proliferation are essential steps in Toxoplasma pathology. The objective of this study was to develop and validate a novel automatic High Content Imaging (HCI) assay to study T. gondii infection and proliferation. We tested various fluorescent markers and strategies of image analysis to obtain an automated method providing results comparable to those from gold standard infection and proliferation assays. No significant difference was observed between the results obtained from the HCI assay and the standard assays (manual fluorescence microscopy and incorporation of [3H]-uracil). We developed here a robust and time-saving assay. This automated technology was then used to screen a library of compounds belonging to four classes of either natural compounds or synthetic derivatives. Inhibition of parasite proliferation and host cell toxicity were measured in the same assay and led to the identification of one hit, a thiosemicarbazone that allows important inhibition of Toxoplasma proliferation while being relatively safe for the host cells. [ABSTRACT FROM AUTHOR]

Drosophila suzukii (the spotted-wing Drosophila) appears to be unsuitable for the development of most Drosophila larval endoparasitoids, be they sympatric or not. Here, we questioned the physiological bases of this widespread failure by characterizing the interactions between D. suzukii and various parasitoid species (Asobara japonica, Leptopilina boulardi, Leptopilina heterotoma and Leptopilina victoriae) and comparing them with those observed with D. melanogaster, a rather appropriate host. All parasitoids were able to oviposit in L1 and L2 larval stages of both hosts but their propensity to parasitize was higher on D. melanogaster. A. japonica and, to a much lesser extent, L. heterotoma, were the two species able to successfully develop in D. suzukii, the failure of the parasitism resulting either in the parasitoid encapsulation (notably with L. heterotoma) or the host and parasitoid deaths (especially with L. boulardi and L. victoriae). Compared to D. melanogaster, encapsulation in D. suzukii was strongly delayed and led, if successful, to the production of much larger capsules in surviving flies and, in the event of failure, to the death of both partners because of an uncontrolled melanization. The results thus revealed a different timing of the immune response to parasitoids in D. suzukii compared to D. melanogaster with a lose-lose outcome for parasitoids (generally unsuccessful development) and hosts (high mortality and possible reduction of the fitness of survivors). Finally, these results might suggest that some European endoparasitoids of Drosophila interact with this pest in the field in an unmeasurable way, since they kill their host without reproductive success. [ABSTRACT FROM AUTHOR]

Schistosomes are parasitic flatworms that infect the vasculature of >200 million people around the world. These long-lived parasites do not appear to provoke blood clot formation or obvious inflammation around them in vivo. Proteins expressed at the host–parasite interface (such as Schistosoma mansoni alkaline phosphatase, SmAP) are likely key to these abilities. SmAP is a glycoprotein that hydrolyses the artificial substrate p -nitrophenyl phosphate in a reaction that requires Mg2+ and at an optimal pH of 9. SmAP additionally cleaves the nucleoside monophosphates AMP, CMP, GMP, and TMP, all with a similar Km (~600–650 μM). Living adult worms, incubated in murine plasma for 1 h, alter the plasma metabolome; a decrease in sphingosine-1-phosphate (S1P) is accompanied by an increase in the levels of its component parts—sphingosine and phosphate. To test the hypothesis that schistosomes can hydrolyze S1P (and not merely recruit or activate a host plasma enzyme with this function), living intravascular life-stage parasites were incubated with commercially obtained S1P and cleavage of S1P was detected. Parasites whose SmAP gene was suppressed using RNAi were impaired in their ability to cleave S1P compared to controls. In addition, recombinant SmAP hydrolyzed S1P. Since extracellular S1P plays key roles in controlling inflammation and platelet aggregation, we hypothesize that schistosome SmAP, by degrading S1P, can regulate the level of this bioactive lipid in the environment of the parasites to control these processes in the worm’s local environment. This is the first report of any parasite being able to cleave S1P. [ABSTRACT FROM AUTHOR]

An editorial is presented on climate change and its effect on infections induced by heminths. It highlights the significant role of the changes in the prospective activity of the parasitic worm's species as well as the emergence and downfall. It also outlines their management through vector control, biotechnology and mass drug administration (MDA).

The Asian fish tapeworm (AFT), Schyzocotyle acheilognathi , is a notorious and highly successful invasive parasite reported in a wide spectrum of freshwater fishes, and new reports of its spread continue to emerge. To date, no thorough review of its worldwide distribution and host associations is available. In the present work, we collected information from 651 articles up until 2017, from which we updated the number of the hosts to 312 fish species and 11 non-fish species, which is quite unusual among helminths. The AFT has spread to all but one continent (Antarctica). The highest number of records are from North America, followed by Asia and Europe. A key feature of its invasive success is its broad environmental tolerance. [ABSTRACT FROM AUTHOR]

Consumer species alter nutrient cycling through nutrient transformation, transfer, and bioturbation. Parasites have rarely been considered in this framework despite their ability to indirectly alter the cycling of nutrients via their hosts. A simple mathematical framework can be used to assess the relative importance of parasite-derived nutrients in an ecosystem. [ABSTRACT FROM AUTHOR]

Four species of Mammomonogamus are known from large African herbivores. A recent study demonstrated that a single Mammomonogamus species was shared by both western lowland gorillas (Gorilla gorilla gorilla) and African forest elephants (Loxodonta cyclotis) in Central African Republic, suggesting lower species diversity than previously described in literature. We examined more than 500 fecal samples collected from sympatric African forest elephants, western lowland gorillas, and African forest buffaloes (Syncerus caffer nanus) at four study sites across Central Africa and examined them by coproscopic methods to detect Mammomonogamus eggs, whichwere found at three of the study sites. Subsequently, sequences of 18S rDNA, 28S rDNA, and cox1 amplified from individual eggs were analyzed. Phylogenetic analyses of both nuclear and mitochondrial DNA revealed two clades: one formed by sequences originating from Gabonese buffaloes and the other comprising gorillas and elephants. The gorilla-elephant clade was further differentiated depending on the locality.We show the existence of at least two distinct species of Mammomonogamus, M. loxodontis in elephants and gorillas and M. nasicola in buffaloes. The available information on Mammomonogamus in African herbivores is reviewed. [ABSTRACT FROM AUTHOR]

The immunochromatographic test (ICT) is a convenient and low-cost method that can rapidly obtain results (10 min) under normal conditions. In this study, we established an ICT assay with two monoclonal antibodies: TgSAG3-3A7 and TgSAG3-4D5 based on the conserved protein of TgSAG3 that can be expressed in all the infective stages of T. gondii. 20 nm gold particles were prepared and conjugated with TgSAG3-3A7 MAb at the concentration of 12.5 μg/mL. TgSAG3-4D5 MAb were used as the capture antibody because of its higher affinity tested by ELISA. The detection limit of the ICT assay was 100 ng with visual detection under optimal conditions of analysis. Positive porcine serum of Cryptosporidium suis , Mycoplasma suis , Streptococcus suis , Salmonella choleraesuis , Cysticercus cellulosae , Isospora suis , and Trichinella spiralis were used to evaluate the specificity of this ICT and no cross-reactivity was observed. 310 porcine serum samples obtained from pig farms in Zhejiang Province, China were detected by this ICT and ELISA kit, 23 positive samples were found by the developed strip with the rate of 7.42% comparing with 22 positive samples detected by the commercially ELISA kit which the positive rate was 7.1%, the relative sensitivity and specificity of this ICT are 100% and 99.65%. Therefore, the ICT established in this study is proved effective, simple, specific and sensitive of T. gondii detection. [ABSTRACT FROM AUTHOR]

Resistance to chemistries of the succinate dehydrogenase inhibiting (SDH1) and quinone outside inhibiting (Qol) fungicides has developed rapidly in populations of Alternaria solani. the cause of early blight of potato. Reduced sensitivity to the anilinopyrimidine (AP) fungicide pyrimethanil has also been identified recently, determining that resistance to three chemical classes of fungicides is present within the A. solani population. Although no mutations have been characterized to confer resistance to APs, in A. solani five point mutations on three AsSdh genes have been determined to convey resistance to SDHIs. and the substitution of phenylalanine with leucine at position 129 (FI29L) in the cytb gene confers resistance to Qols. The objective of this study was to investigate the parasitic fitness of A. solani isolates with resistance to one or more of these chemical classes. A total of 120 A. solani isolates collected from various geographical locations around the United States were chosen for in vitro assessment, and 60 of these isolates were further evaluated in vivo. Fitness parameters measured were (i) spore germination in vitro, (ii) mycelial expansion in vitro, and (iii) aggressiveness in vivo. No significant differences in spore germination or mycelial expansion (P = 0.44 and 0.51, respectively) were observed among wild-type and fungicideresistant isolates in vitro. Only A. solani isolates possessing the D123E mutation were shown to be significantly more aggressive in vivo (P < 0.0001) compared with wild-type isolates. These results indicate that fungicide-resistant A. solani isolates have no significant fitness penalties compared with sensitive isolates under the parameters evaluated regardless of the presence or absence of reduced sensitivity to multiple chemical classes. Results of these studies suggest that A. solani isolates with multiple fungicide resistances may compete successfully with wild-type isolates under field conditions. [ABSTRACT FROM AUTHOR]

In total, 13 commercial wheat cultivars around China and four races of Puccinia striiformis f. sp. tritici (namely, CYR32, CYR33, G22-9, and G22-14) were employed for a test of relative parasitic fitness (RPF) using the drop method. The RPF values were measured, including the urediniospore germination rate, the latent period, the uredinial length, the uredinial density, the infection area, the sporulation intensity, the lesion expansion speed, and the sporulation period. The results indicated that the parameters of relative parasitic fitness of the four P. striiformis f. sp. tritici races on the 13 wheat cultivars were significantly different (P = 0.00) in sporulation intensity, lesion expansion speed, uredinial length, sporulation period, uredinial density, and latent period. The urediniospore germination rates of the four P. striiformis f. sp. tritici races for the test were significantly different (P = 0.00), whereas no correlation with the different cultivars was observed (P = 1.00). The infection areas of the tested races on the different cultivars were significantly different (P = 0.00) but there were no obvious manifestations among the various races (P = 0.20). Principal component analysis (PCA) showed that the sporulation intensity represented sporulation capacity and scalability, the latent period indicated infection ability, and the urediniospore germination rate represented urediniospore vigor, all of which fully contributed to the RPF in the interaction of the four races and 13 wheat cultivars, which was calculated by the following formula: RPF = (sporulation intensity x urediniospore germination rate)/latent period. The sporulation and infection of G22-9 on the 13 large-scale cultivated cultivars were the highest, and the RPF of G22-9 was higher than that of the predominant races, CYR32 and CYR33. This result suggested that G22-9 could become a new predominant race and potentially cause epidemics of wheat stripe rust in China. To prevent potential epidemics, susceptible wheat cultivars should be withdrawn from production and breeding programs should reduce the use of YrlO and Yr26 and use other more effective resistance genes in combination with nonrace-specific resistance for developing wheat cultivars with durable resistance to stripe rust. [ABSTRACT FROM AUTHOR]

Parasitoid wasps of the order Hymenoptera, the most diverse groups of animals, are important natural enemies of arthropod hosts in natural ecosystems and can be used in biological control. To date, only one neuropeptidome of a parasitoid wasp, Nasonia vitripennis, has been identified. This study aimed to identify more neuropeptides of parasitoid wasps, by using a well-established workflow that was previously adopted for predicting insect neuropeptide sequences. Based on publicly accessible databases, totally 517 neuropeptide precursors from 24 parasitoid wasp species were identified; these included five neuropeptides (CNMamide, FMRFamide-like, ITG-like, ion transport peptide-like and orcokinin B) that were identified for the first time in parasitoid wasps, to our knowledge. Next, these neuropeptides from parasitoid wasps were compared with those from other insect species. Phylogenetic analysis suggested the divergence of AST-CCC within Hymenoptera. Further, the encoding patterns of CAPA/PK family genes were found to be different between Hymenoptera species and other insect species. Some neuropeptides that were not found in some parasitoid superfamilies (e.g., sulfakinin), or considerably divergent between different parasitoid superfamilies (e.g., sNPF) might be related to distinct physiological processes in the parasitoid life. Information of neuropeptide sequences in parasitoid wasps can be useful for better understanding the phylogenetic relationships of Hymenoptera and further elucidating the physiological functions of neuropeptide signaling systems in parasitoid wasps. [ABSTRACT FROM AUTHOR]

Circadian rhythms enable organisms to synchronise the processes underpinning survival and reproduction to anticipate daily changes in the external environment. Recent work shows that daily (circadian) rhythms also enable parasites to maximise fitness in the context of ecological interactions with their hosts. Because parasite rhythms matter for their fitness, understanding how they are regulated could lead to innovative ways to reduce the severity and spread of diseases. Here, we examine how host circadian rhythms influence rhythms in the asexual replication of malaria parasites. Asexual replication is responsible for the severity of malaria and fuels transmission of the disease, yet, how parasite rhythms are driven remains a mystery. We perturbed feeding rhythms of hosts by 12 hours (i.e. diurnal feeding in nocturnal mice) to desynchronise the host’s peripheral oscillators from the central, light-entrained oscillator in the brain and their rhythmic outputs. We demonstrate that the rhythms of rodent malaria parasites in day-fed hosts become inverted relative to the rhythms of parasites in night-fed hosts. Our results reveal that the host’s peripheral rhythms (associated with the timing of feeding and metabolism), but not rhythms driven by the central, light-entrained circadian oscillator in the brain, determine the timing (phase) of parasite rhythms. Further investigation reveals that parasite rhythms correlate closely with blood glucose rhythms. In addition, we show that parasite rhythms resynchronise to the altered host feeding rhythms when food availability is shifted, which is not mediated through rhythms in the host immune system. Our observations suggest that parasites actively control their developmental rhythms. Finally, counter to expectation, the severity of disease symptoms expressed by hosts was not affected by desynchronisation of their central and peripheral rhythms. Our study at the intersection of disease ecology and chronobiology opens up a new arena for studying host-parasite-vector coevolution and has broad implications for applied bioscience. [ABSTRACT FROM AUTHOR]

Myxosporean infections can cause severe damage to commercially grown tilapia. Here, we report a novel myxosporean that was found in gills of Oreochromis aureus male × Oreochromis niloticus female, which is an important aquaculture tilapia hybrid in Israel. Three-month-old fish were found to have cysts located in gill muscle tissue, which were filled with both immature and mature spores. Affected fish displayed higher mortality rate. Spore dimensions (10.8 ± 0.7 μm length × 6.8 ± 0.6 μm width) and molecular characterization using 18S ribosomal DNA revealed that the unknown parasite belongs in the Myxobolus clade. Based on the infection site, spore morphology and molecular characterization, we describe this parasite as Myxobolus bejeranoi n. sp. (MF401455). Phylogenetic analysis showed that the new species is most closely related to two Myxobolus spp. from O. niloticus in Egypt and Ghana. [ABSTRACT FROM AUTHOR]

The article offers information on reproductive and nonreproductive swarming in honey bees and discusses whether it adapts to pathogens or not. Topics discussed include the incidence of pathogens in honey bee colonies and honey bee swarming behavior, the importance of the population health of honey bees, and the role of nonreproductive swarming in behavioral immunity for the honey bees.

The reproductive season is energetically costly as revealed by elevated glucocorticoid concentrations, constrained immune functions and an increased risk of infections. Social allies and affiliative interactions may buffer physiological stress responses and thereby alleviate associated effects. In the present study, we investigated the seasonal differences of immune reactive corticosterone metabolite concentrations, endoparasite burden (nematode eggs and coccidian oocysts) and affiliative interactions in northern bald ibis (Geronticus eremita), a critically endangered bird. In total, 43 individually marked focal animals from a free-ranging colony were investigated. The analyses included a description of initiated and received affiliative interactions, pair bond status as well as seasonal patterns of hormone and endoparasite levels. During the reproductive season, droppings contained parasite eggs more often and corticosterone metabolite levels were higher as compared to the period after reproduction. The excretion rate of endoparasite products was lower in paired individuals than in unpaired ones, but paired animals exhibited higher corticosterone metabolite concentrations than unpaired individuals. Furthermore, paired individuals initiated affiliative behaviour more frequently than unpaired ones. This suggests that the reproductive season influences the excretion patterns of endoparasite products and corticosterone metabolites and that affiliative interactions between pair partners may positively affect endoparasite burden during periods of elevated glucocorticoid levels. Being embedded in a pair bond may have a positive impact on individual immune system and parasite resistance. [ABSTRACT FROM AUTHOR]

Trypanosoma cruzi, the etiological agent of Chagas disease, consumes glucose and amino acids depending on the environmental availability of each nutrient during its complex life cycle. For example, amino acids are the major energy and carbon sources in the intracellular stages of the T. cruzi parasite, but their consumption produces an accumulation of NH4+ in the environment, which is toxic. These parasites do not have a functional urea cycle to secrete excess nitrogen as low-toxicity waste. Glutamine synthetase (GS) plays a central role in regulating the carbon/nitrogen balance in the metabolism of most living organisms. We show here that the gene TcGS from T. cruzi encodes a functional glutamine synthetase; it can complement a defect in the GLN1 gene from Saccharomyces cerevisiae and utilizes ATP, glutamate and ammonium to yield glutamine in vitro. Overall, its kinetic characteristics are similar to other eukaryotic enzymes, and it is dependent on divalent cations. Its cytosolic/mitochondrial localization was confirmed by immunofluorescence. Inhibition by Methionine sulfoximine revealed that GS activity is indispensable under excess ammonium conditions. Coincidently, its expression levels are maximal in the amastigote stage of the life cycle, when amino acids are preferably consumed, and NH4+ production is predictable. During host-cell invasion, TcGS is required for the parasite to escape from the parasitophorous vacuole, a process sine qua non for the parasite to replicate and establish infection in host cells. These results are the first to establish a link between the activity of a metabolic enzyme and the ability of a parasite to reach its intracellular niche to replicate and establish host-cell infection. [ABSTRACT FROM AUTHOR]

The Zr, Hf, Y and lanthanide (REE) distribution in biological tissues of Sabella spallanzanii and Styela plicata species collected from two harbours from the northern Sicily is studied for providing information regarding the Zr, Hf and REE uptake from the environment. Previous studies determined the fractionation of dissolved REE scavenged on binding sites onto biological surfaces. By comparing the recognised shale-normalised REE patterns of studied samples with evidence from reference data, the observed behaviour of these elements in biological tissues of Sabella spallanzanii and Styela plicata is interpreted to result from the preferential uptake of intermediate REE onto carboxylic sites. Moreover, the relationship observed between the Fe content and Zr/Hf ratio suggests that preferential Hf accumulation occurs via siderophore-like binding sites. Features of the REE bioaccumulation factors (BAF), in addition to the absolute La, Ce and Sm contents and Zr-Hf fractionation, allow definition of the different origins of studied elements in the investigated localities. Higher BAF values for La and Ce associated with larger REE contents and lower Zr/Hf values strongly suggest that the environmental REE distribution in the Termini Imerese harbour is influenced by the delivery of particles from industrial sources and power plants. On the contrary, the REE contents of biological tissues collected in the Cala tourist harbour are affected by the dust dissolution from automotive traffic. These results suggest that the geochemical behaviour of REE and Zr/Hf signature can be used in environmental studies of biological tissues for reconstructing the nature of anthropogenic contaminations. [ABSTRACT FROM AUTHOR]

Target Product Profiles (TPPs) are process tools providing product requirements to guide researchers, developers and manufacturers in their efforts to develop effective and useful products such as biologicals, drugs or diagnostics. During a WHO Stakeholders Meeting on Taenia solium diagnostics, several TPPs were initiated to address diagnostic needs for different stages in the parasite’s transmission (taeniasis, human and porcine cysticercosis). Following the meeting, draft TPPs were completed and distributed for consultation to 100 people/organizations, including experts in parasitology, human and pig cysticercosis, diagnostic researchers and manufacturers, international organizations working with neglected or zoonotic diseases, Ministries of Health and Ministries of Livestock in some of the endemic countries, WHO regional offices and other interested parties. There were 53 respondents. All comments and feedback received were considered and discussions were held with different experts according to their area of expertise. The comments were consolidated and final TPPs are presented here. They are considered to be live documents which are likely to undergo review and updating in the future when new knowledge and technologies become available. [ABSTRACT FROM AUTHOR]

Cuscuta spp. (i.e., dodders) are stem parasites that naturally graft to their host plants to extract water and nutrients; multiple adjacent hosts are often parasitized by one or more Cuscuta plants simultaneously, forming connected plant clusters. Metabolites, proteins, and mRNAs are known to be transferred from hosts to Cuscuta, and Cuscuta bridges even facilitate host-to-host virus movement. Whether Cuscuta bridges transmit ecologically meaningful signals remains unknown. Here we show that, when host plants are connected by Cuscuta bridges, systemic herbivory signals are transmitted from attacked plants to unattacked plants, as revealed by the large transcriptomic changes in the attacked local leaves, undamaged systemic leaves of the attacked plants, and leaves of unattacked but connected hosts. The interplant signaling is largely dependent on the jasmonic acid pathway of the damaged local plants, and can be found among conspecific or heterospecific hosts of different families. Importantly, herbivore attack of one host plant elevates defensive metabolites in the other systemic Cuscuta bridge-connected hosts, resulting in enhanced resistance against insects even in several consecutively Cuscuta-connected host plants over long distances (> 100 cm). By facilitating plant-to-plant signaling, Cuscuta provides an information-based means of countering the resource-based fitness costs to their hosts. [ABSTRACT FROM AUTHOR]

3′-nucleotidase/nuclease (3′NT/NU) is a bi-functional enzyme that is able to hydrolyze 3′-monophosphorylated nucleotides and nucleic acids. This review summarizes the major molecular and biochemical properties of this enzyme in different trypanosomatid species. Sequence analysis of the gene encoding 3′NT/NU in Leishmania and Crithidia species showed that the protein possesses five highly conserved regions that are characteristic of members of the class I nuclease family. 3′NT/NU presents a molecular weight of approximately 40 kDa, which is conserved among the studied species. Throughout the review, we discuss inhibitors and substrate specificity, relating them to the putative structure of the enzyme. Finally, we present the major biological roles performed by 3′NT/NU. The involvement of 3′NT/NU in the purine salvage pathway was confirmed by the increase of activity and expression of the enzyme when the parasites were submitted to purine starvation. The generation of extracellular adenosine is also important to the modulation of the host immune response. Interaction assays involving Leishmania parasites and macrophages indicated that 3′-nucleotidase activity increases the association index between them. Recently, it was shown that 3′NT/NU plays a role in parasite escape from neutrophil extracellular traps, one of the first mechanisms of the host immune system for preventing infection. [ABSTRACT FROM AUTHOR]

Proliferation of Leishmania (L.) parasites depends on polyamine availability, which can be generated by the L-arginine catabolism and the enzymatic activity of arginase (ARG) of the parasites and of the mammalian hosts. In the present study, we characterized and compared the arginase (arg) genes from pathogenic L. major and L. tropica and from non-pathogenic L. tarentolae. We quantified the level of the ARG activity in promastigotes and macrophages infected with pathogenic L. major and L. tropica and non-pathogenic L. tarentolae amastigotes. The ARG's amino acid sequences of the pathogenic and non-pathogenic Leishmania demonstrated virtually 98.6% and 88% identities with the reference L. major Friedlin ARG. Higher ARG activity was observed in all pathogenic promastigotes as compared to non-pathogenic L. tarentolae. In vitro infection of human macrophage cell line (THP1) with pathogenic and non-pathogenic Leishmania spp. resulted in increased ARG activities in the infected macrophages. The ARG activities present in vivo were assessed in susceptible BALB/c and resistant C57BL/6 mice infected with L. major, L. tropica and L. tarentolae. We demonstrated that during the development of the infection, ARG is induced in both strains of mice infected with pathogenic Leishmania. However, in L. major infected BALB/c mice, the induction of ARG and parasite load increased simultaneously according to the time course of infection, whereas in C57BL/6 mice, the enzyme is upregulated solely during the period of footpad swelling. In L. tropica infected mice, the footpads' swellings were slow to develop and demonstrated minimal cutaneous pathology and ARG activity. In contrast, ARG activity was undetectable in mice inoculated with the non-pathogenic L. tarentolae. Our data suggest that infection by Leishmania parasites can increase ARG activity of the host and provides essential polyamines for parasite salvage and its replication. Moreover, the ARG of Leishmania is vital for parasite proliferation and required for infection in mice. ARG activity can be used as one of the main marker of the disease severity. [ABSTRACT FROM AUTHOR]

Hosts can counteract parasites through defences based on resistance and/or tolerance. The mechanistic basis of tolerance, which involve defensive mechanisms minimizing parasite damage after a successful parasitic attack, remains poorly explored in the study of cuckoo-host interactions. Here, we experimentally explore the possibility that the risk of great spotted cuckoo Clamator glandarius parasitism may induce tolerance defences in magpie Pica pica hosts through plasticity in life-history traits. We predict that magpies exposed to auditory cues indicating high parasitism risk will more likely exhibit resistance and/or modify their life-history traits to minimize parasitism costs (i.e. tolerance) compared to magpies under low parasitism risk. We found that manipulating the perceived parasitism risk did not affect host resistance (i.e. rejection of parasitic eggs) nor host life-history traits. Unexpectedly, host’s egg volume increased over the season in nests exposed to auditory cues of control non-harmful hoopoes Upupa epops. Our results do not provide support for inducible defences (either based on resistance or tolerance) in response to risk of parasitism in magpie hosts. Even so, we encourage studying plastic expression of breeding strategies in response to risk of cuckoo parasitism to achieve a better understanding of the mechanistic basis of tolerance defences. [ABSTRACT FROM AUTHOR]

The hydatid fluid (HF) that fills Echinococcus multilocularis metacestode vesicles is a complex mixture of proteins from both parasite and host origin. Here, a LC-MS/MS approach was used to compare the HF composition of E. multilocularis H95 and G8065 isolates (EmH95 and EmG8065, respectively), which present differences in terms of growth and fertility. Overall, 446 unique proteins were identified, 392 of which (88%) were from parasite origin and 54 from culture medium. At least 256 of parasite proteins were sample exclusive, and 82 of the 136 shared proteins presented differential abundance between E. multilocularis isolates. The parasite's protein repertoires in EmH95 and EmG8065 HF samples presented qualitative and quantitative differences involving antigens, signaling proteins, proteolytic enzymes, protease inhibitors and chaperones, highlighting intraspecific singularities that could be correlated to biological features of each isolate. The repertoire of medium proteins found in the HF was also differential between isolates, and the relevance of the HF exogenous protein content for the parasite's biology is discussed. The repertoires of identified proteins also provided potential molecular markers for important biological features, such as parasite growth rate and fertility, as well potential protein targets for the development of novel diagnostic and treatment strategies for alveolar echinococcosis. Biological significance E. multilocularis metacestode infection of mammal hosts involve complex interactions mediated by excretory/secretory (ES) products. The hydatid fluid (HF) that fills the E. multilocularis metacestode vesicles contains complex repertoires of parasite ES products and host proteins that mediate important molecular interactions determinant for parasite survival and development, and, consequently, to the infection outcome. HF has been also extensively reported as the main source of proteins for the immunodiagnosis of echinococcosis. The performed proteomic analysis provided a comprehensive profiling of the HF protein composition of two E. multilocularis isolates. This allowed us to identify proteins of both parasite and exogenous (medium) origin, many of which present significant differential abundances between parasite isolates and may correlate to their differential biological features, including fertility and growth rate. [ABSTRACT FROM AUTHOR]

Parasites are ubiquitous in the wild and by imposing fitness costs on their hosts they constitute an important selection factor. One of the most common parasites of wild birds are Plasmodium and Haemoproteus, protozoans inhabiting the blood, which cause avian malaria and malaria-like disease, respectively. Although they are expected to cause negative effects in infected individuals, in many cases studies in natural populations failed to detect such effect. Using data from seven breeding seasons (2008-2014), we applied a multistate capture-mark-recapture approach to study the effect of infection with malaria and malaria-like parasites, individual age and sex on the probability of survival and recapture rate in a small passerine, the blue tit Cyanistes caeruleus, inhabiting the island of Gotland, Sweden. We found no effect of infection on survival prospects. However, the recapture rate of infected individuals was higher than that of uninfected ones. Thus, while our data do not support the presence of infection costs in terms of host survival, it suggests that parasites from the genera Plasmodium and Haemoproteus may affect some aspects of host behaviour, which translates into biased estimation of infection frequency at the population level. [ABSTRACT FROM AUTHOR]

While parasites serve as prey, it is unclear how the spatial distribution of parasite predators provides transmission control and influences patterns of parasitism. Because many of its organisms are sessile, the rocky intertidal zone is a valuable but little used system to understand spatial patterns of parasitism and elucidate the underlying mechanisms driving these patterns. Sea anemones and barnacles are important space competitors in the rocky intertidal zone along the Pacific coast of North America. Anemones are voracious, indiscriminate predators; thus, they may intercept infectious stages of parasites before they reach a host. We investigate whether a sea anemone protects an associated barnacle from parasitism by Hemioniscus balani, an isopod parasitic castrator. At Coal Oil Point, Santa Barbara, California USA, 29% of barnacles were within 1 cm from an anemone at the surveyed tidal height. Barnacles associated with anemones had reduced parasite prevalence and higher reproductive productivity than those remote from sea anemones. In the laboratory, anemones readily consumed the transmission stage of the parasite. Hence, anemone consumption of parasite transmission stages may provide a mechanism by which community context regulates parasite prevalence at a local scale. Our results suggest predation may be an important process providing parasite transmission control. [ABSTRACT FROM AUTHOR]

The boron element possesses a range of different effects on living beings. It is essential to beneficial at low concentrations, but toxic at excessive concentrations. Recently, some boron-based compounds have been identified as promising molecules against Trypanosoma brucei , the causative agent of sleeping sickness. However, until now, the boron metabolism and its access route into the parasite remained elusive. The present study addressed the permeability of T. brucei aquaglyceroporins (TbAQPs) for boric acid, the main natural boron species. To this end, the three TbAQPs were expressed in Saccharomyces cerevisiae and Xenopus laevis oocytes. Our findings in both expression systems showed that all three TbAQPs are permeable for boric acid. Especially TbAQP2 is highly permeable for this compound, displaying one of the highest conductances reported for a solute in these channels. Additionally, T. brucei aquaglyceroporin activities were sensitive to pH. Taken together, these results establish that TbAQPs are channels for boric acid and are highly efficient entry pathways for boron into the parasite. Our findings stress the importance of studying the physiological functions of boron and their derivatives in T. brucei , as well as the pharmacological implications of their uptake by trypanosome aquaglyceroporins. [ABSTRACT FROM AUTHOR]

Recent years have witnessed a dramatic increase in diseases that are ascribed to alter metabolism eventually resulting in conditions including obesity, type-2 diabetes (T2D), cardiovascular disease and metabolic syndrome (MetS). Of the many factors to which this rise has been attributed, including diet, physical activity and inflammation, several studies have correlated these disease states with alterations in gut microbiota. Simultaneously, studies have demonstrated the ability of parasites to alter microbial communities within their shared niche, leading to alterations in inflammatory processes. However, very few reports have addressed how these changes to the microbiome may be a mechanism by which parasites influence not only inflammation but also metabolic states. In this review, we attempt to draw parallels between the three capacious topics and examine the interrelationship between them. [ABSTRACT FROM AUTHOR]

Scabies, caused by the mite Sarcoptes scabiei , is a highly contagious parasitic disease that affects millions of people and other mammals worldwide. Calmodulin (CaM) is an important calcium sensor that participates in various critical physiological processes. In this study, the CaM of Sarcoptes scabiei (SsCaM) was cloned and expressed, and sequence analyses were performed using bioinformatics tools. Recombinant SsCaM (rSsCaM) was used to detect antigenicity using immunoblotting assays, and the serodiagnostic potential of rSsCaM was assessed by indirect enzyme-linked immuno-sorbent assay (ELISA). The calcium binding properties and 8-anilinonaphthalene-1-sulfonic acid (ANS) fluorescence of rSsCaM were also measured. The results indicated that SsCaM contains a 450-bp open reading frame that encodes for a polypeptide with 149 amino acids, and SsCaM was expressed as a soluble protein. Multiple sequence alignment and phylogenetic analyses indicated similarity and genetic distance between SsCaM and other species. The calcium binding properties and ANS fluorescence of rSsCaM indicated typical calcium binding characteristics. Immunolocalizaton assay showed that SsCaM was widespread in S. scabiei . SsCaM-based ELISA exhibited a sensitivity of 87.5% (28/32) and a specificity of 22.5% (9/40) for detecting anti-CaM antibodies in the sera of naturally infected rabbits. The findings of this study provide a comprehensive molecular characterization of SsCaM and suggest that rSsCaM is inappropriate for detecting S. scabiei . The results may also contribute to future studies on the molecular characteristics of the CaM of parasites. [ABSTRACT FROM AUTHOR]

Plasmodium falciparum parasites, the causative agents of malaria, modify their host erythrocyte to render them permeable to supplementary nutrient uptake from the plasma and for removal of toxic waste. Here we investigate the contribution of the rhoptry protein RhopH2, in the formation of new permeability pathways (NPPs) in Plasmodium-infected erythrocytes. We show RhopH2 interacts with RhopH1, RhopH3, the erythrocyte cytoskeleton and exported proteins involved in host cell remodeling. Knockdown of RhopH2 expression in cycle one leads to a depletion of essential vitamins and cofactors and decreased de novo synthesis of pyrimidines in cycle two. There is also a significant impact on parasite growth, replication and transition into cycle three. The uptake of solutes that use NPPs to enter erythrocytes is also reduced upon RhopH2 knockdown. These findings provide direct genetic support for the contribution of the RhopH complex in NPP activity and highlight the importance of NPPs to parasite survival. [ABSTRACT FROM AUTHOR]

All animals, whether vertebrate or invertebrate, must be capable of reacting to acute stressors, such as escaping from predators, and most do so with a suite of transient physiological changes that temporarily enhance survival. Some of these changes include mobilization of immune cells and increased cardiac output. A small but growing number of studies have begun to show that certain parasites appear capable of modifying such responses. We addressed this topic using a natural host and parasite system, that is, a nematode (Chondronema passali) that parasitizes horned passalus beetles, Odontotaenius disjunctus (family Passalidae), of the eastern United States.With a series of experiments, we sought to determine whether this parasite affects (1) the immune reaction to stress, (2) the output of stress-induced alarm calls, or (3) the increase in heart rate that occurs in response to acute stressors, with the stressors being mechanical or thermal. Results showed that hemocyte density increased after both stressors in nonparasitized beetles but did not increase in parasitized beetles. While mobilization of immune cells would enhance host immunity during stress, this would also be damaging to the nematode, so this scenario appears to benefit the parasite. We found no evidence that the nematode suppresses the overall reaction to stress (or prevents stress from occurring), since parasitized beetles did not differ from nonparasitized ones in alarm call rates or in heart beat frequency after exposure to mechanical stressors. Suppression of the host's normal immune reaction to stressful stimuli could translate to delayed or even reduced wound healing or pathogen resistance during these events. This project is a rare demonstration of parasite manipulation of host immune response to acute stress and should stimulate further investigations into the interactive nature of stress and parasites. [ABSTRACT FROM AUTHOR]

Inorganic phosphate (P i ) is an essential nutrient for all organisms because it is required for a variety of biochemical processes, such as signal transduction and the synthesis of phosphate-containing biomolecules. Assays of 32 P i uptake performed in the absence or in the presence of Na + indicated the existence of a Na + -dependent and a Na + -independent P i transporter in Phytomonas serpens . Phylogenetic analysis of two hypothetical protein sequences of Phytomonas (EM1) showed similarities to the high-affinity P i transporters of Saccharomyces cerevisiae : Pho84, a Na + -independent P i transporter, and Pho89, a Na + -dependent P i transporter. Plasma membrane depolarization by FCCP, an H + ionophore, strongly decreased P i uptake via both Na + -independent and Na + -dependent carriers, indicating that a membrane potential is essential for P i influx. In addition, the furosemide-sensitive Na + -pump activity in the cells grown in low P i conditions was found to be higher than the activity detected in the plasma membrane of cells cultivated at high P i concentration, suggesting that the up-regulation of the Na + -ATPase pump could be related to the increase of P i uptake by the Pho89p Na + :P i symporter. Here we characterize for the first time two inorganic phosphate transporters powered by Na + and H + gradients and activated by low P i availability in the phytopathogen P. serpens . [ABSTRACT FROM AUTHOR]

-2019 PLOS Genetics Research Prize: Fruit fly school - language and dialects for communicating a threat Keywords: Editorial; Biology and life sciences; Neuroscience; Cognitive science; Cognitive psychology; Learning; Human learning; Psychology; Social sciences; Learning and memory; Research and analysis methods; Animal studies; Experimental organism systems; Model organisms; Drosophila melanogaster; Animal models; Organisms; Eukaryota; Animals; Invertebrates; Arthropoda; Insects; Drosophila; Genetics; Sociology; Communications; Social communication; Hymenoptera; Wasps; Parasitology; Parasite physiology; People and places; Population groupings; Professions; Teachers 3 Kacsoh BZ, Bozler J, Bosco G (2018) Drosophila species learn dialects through communal living. Neural circuitry of social learning in Drosophila requires multiple inputs to facilitate inter-species communication. [Extracted from the article]

Investigation of blood parasites from eleven Corythaeola cristata (Vieillot, 1816) imported from Tanzania to the Jurong Bird Park, Singapore reveals a high prevalence of Haematozoa (81.8%) and the presence of a polyparasitism by microfilaria, Plasmodium and a distinctive new species of haemoproteid: Haemoproteus (Parahaemoproteus) minchini new species. The present study provides a description of the parasite based on the morphology and morphometric measurements of its blood stages that highlights a sexual dimorphism as well as its larger size when compared to the other haemoproteid reported from the Musophagiformes (i.e, Haemoproteus montezi Travassos Santos Dias, 1953). The study also provides a molecular characterisation of Haemoproteus (Parahaemoproteus) minchini new species by four different gene fragments (cytochrome b, cytochrome c oxidase 1, caseinolytic protease C and elongation factor Tu) spread across the organellar genomes of the parasite. Phylogenetic analyses were performed for each gene to assess the genetic relationship of this new parasite species with the other available sequences of identified avian haemoproteids, and it is referable to the subgenus Parahaemoproteus. This study also proposes for the first time a sequence of the elongation factor Tu gene for a haemoproteid parasite. The geographic origin and the possible pathogeny and pathology of Haemoproteus (Parahaemoproteus) minchini new species are discussed, as is the importance of using these data in conjunction with morphological and the molecular methods to study avian Haemosporidia. [ABSTRACT FROM AUTHOR]

During parasitoid development, the immature parasitoid is confined to the host species. As a result, any potential to modify the physiology or behaviour of the host could play an important role in parasitoid fitness. The potential for host manipulation by the aphid parasitoid Aphidius avenae to increase cold thermotolerance was investigated using the aphid host species Metopolophium dirhodum and Sitobion avenae. Aphids were parasitized at L3/L4 instar stage (5 d old) and allowed to develop into pre-reproductive adults (10 d old) containing a 5 d old parasitoid larva. A control group was created of non-parasitized pre-reproductive adults (10 d old). The inherent physiological thermotolerance (LT50) and potential behavioural thermoregulation (behaviour in a declining temperature regime) of parasitized and non-parasitized aphids were investigated. Results revealed no effect of parasitism on the physiological thermotolerance of S. avenae and M. dirhodum. Significant differences in the behaviour of parasitized and non-parasitized aphids were observed, in addition to differences between host species, and such behaviours are discussed in view of the potential for host manipulation. [ABSTRACT FROM AUTHOR]

Palmitoylation is the post-translational reversible addition of the acyl moiety, palmitate, to cysteine residues of proteins and is involved in regulating protein trafficking, localization, stability and function. The Aspartate-Histidine-Histidine-Cysteine (DHHC) protein family, named for their highly conserved DHHC signature motif, is thought to be responsible for catalysing protein palmitoylation. Palmitoylation is widespread in all eukaryotes, including the malaria parasite, Plasmodium falciparum, where over 400 palmitoylated proteins are present in the asexual intraerythrocytic schizont stage parasites, including proteins involved in key aspects of parasite maturation and development. The P. falciparum genome includes 12 proteins containing the conserved DHHC motif. In this study, we adapted a palmitoyl-transferase activity assay for use with P. falciparum proteins and demonstrated for the first time that P. falciparum DHHC proteins are responsible for the palmitoylation of P. falciparum substrates. This assay also reveals that multiple DHHCs are capable of palmitoylating the same substrate, indicating functional redundancy at least in vitro. To test whether functional redundancy also exists in vivo, we investigated the endogenous localization and essentiality of a subset of schizont-expressed PfDHHC proteins. Individual PfDHHC proteins localized to distinct organelles, including parasite-specific organelles such as the rhoptries and inner membrane complex. Knock-out studies identified individual DHHCs that may be essential for blood-stage growth and others that were functionally redundant in the blood stages but may have functions in other stages of parasite development. Supporting this hypothesis, disruption of PfDHHC9 had no effect on blood-stage growth but reduced the formation of gametocytes, suggesting that this protein could be exploited as a transmission-blocking target. The localization and stage-specific expression of the DHHC proteins may be important for regulating their substrate specificity and thus may provide a path for inhibitor development. [ABSTRACT FROM AUTHOR]

The Plasmodium translocon for exported proteins (PTEX) has been established as the machinery responsible for the translocation of all classes of exported proteins beyond the parasitophorous vacuolar membrane of the intraerythrocytic malaria parasite. Protein export, particularly in the asexual blood stage, is crucial for parasite survival as exported proteins are involved in remodelling the host cell, an essential process for nutrient uptake, waste removal and immune evasion. Here, we have truncated the conserved C-terminus of one of the essential PTEX components, PTEX150, in Plasmodium falciparum in an attempt to create mutants of reduced functionality. Parasites tolerated C-terminal truncations of up to 125 amino acids with no reduction in growth, protein export or the establishment of new permeability pathways. Quantitative proteomic approaches however revealed a decrease in other PTEX subunits associating with PTEX150 in truncation mutants, suggesting a role for the C-terminus of PTEX150 in regulating PTEX stability. Our analyses also reveal three previously unreported PTEX-associated proteins, namely PV1, Pf113 and Hsp70-x (respective PlasmoDB numbers; PF3D7_1129100, PF3D7_1420700 and PF3D7_0831700) and demonstrate that core PTEX proteins exist in various distinct multimeric forms outside the major complex. [ABSTRACT FROM AUTHOR]