Heterodera ustinovi (grass cyst nematode).

There is limited evidence available to suggest that H. ustinovi is invasive. The identical COI halpotypes shared between the USA and Europe most likely represent recent introductions. The small amount of genetic information from North America suggests that H. ustinovi is widespread in the south west (Arizona), midwest (Ohio) and New England states, with little genetic differentiation. H. ustinovi has not been found on any plant species in the USA other than introduced Agrostis species and in turf/golf course settings. A lot of nematodes are transported in turf from turf farms. The initial discovery on native Agrostis in the Ukraine would suggest a potential native parasite existing on a native plant species, but, there are very few of samples on which to base these comparisons.

Heterodera ustinovi (grass cyst nematode).

There is limited evidence available to suggest that H. ustinovi is invasive. The identical COI halpotypes shared between the USA and Europe most likely represent recent introductions. The small amount of genetic information from North America suggests that H. ustinovi is widespread in the south west (Arizona), midwest (Ohio) and New England states, with little genetic differentiation. H. ustinovi has not been found on any plant species in the USA other than introduced Agrostis species and in turf/golf course settings. A lot of nematodes are transported in turf from turf farms. The initial discovery on native Agrostis in the Ukraine would suggest a potential native parasite existing on a native plant species, but, there are very few of samples on which to base these comparisons.

β-Hexosaminidases Along the Secretory Pathway of Nicotiana benthamiana Have Distinct Specificities Toward Engineered Helminth N-Glycans on Recombinant Glycoproteins

Secretions of parasitic worms (helminths) contain a wide collection of immunomodulatory glycoproteins with the potential to treat inflammatory disorders, like autoimmune diseases. Yet, the identification of single molecules that can be developed into novel biopharmaceuticals is hampered by the limited availability of native parasite-derived proteins. Recently, pioneering work has shown that helminth glycoproteins can be produced transiently in Nicotiana benthamiana plants while simultaneously mimicking their native helminth N-glycan composition by co-expression of desired glycosyltransferases. However, efficient “helminthization” of N-glycans in plants by glyco-engineering seems to be hampered by the undesired truncation of complex N-glycans by β-N-acetyl-hexosaminidases, in particular when aiming for the synthesis of N-glycans with antennary GalNAcβ1-4GlcNAc (LacdiNAc or LDN). In this study, we cloned novel β-hexosaminidase open reading frames from N. benthamiana and characterized the biochemical activity of these enzymes. We identified HEXO2 and HEXO3 as enzymes responsible for the cleavage of antennary GalNAc residues of N-glycans on the model helminth glycoprotein kappa-5. Furthermore, we reveal that each member of the HEXO family has a distinct specificity for N-glycan substrates, where HEXO2 has strict β-galactosaminidase activity, whereas HEXO3 cleaves both GlcNAc and GalNAc. The identification of HEXO2 and HEXO3 as major targets for LDN cleavage will enable a targeted genome editing approach to reduce undesired processing of these N-glycans. Effective knockout of these enzymes could allow the production of therapeutically relevant glycoproteins with tailor-made helminth N-glycans in plants.

Defence responses of native and invasive plants to the native generalist vine parasite Cassytha pubescens – anatomical and functional studies

We investigated the responses of two invasive and two native host species to the parasitic vine Cassytha pubescens R.Br. using glasshouse experiments. We assessed growth of the parasite and its hosts, and anatomy and functionality of haustoria. Target hosts were infected using C. pubescens already established on a donor host. This enabled measurement of growth in target hosts that were detached (parasite connection severed) or not from the donor host. Haustorial connections to hosts were investigated using histological methods. We tested the functionality of haustoria in one invasive and one native host using radiolabelled phosphorus (32P). After it was severed from the donor host, C. pubescens grew poorly on the native host, Acacia myrtifolia (Sm.)Willd. This was likely due to a lack of effective functional haustorial development because although haustoria were firmly attached and morphologically alike those formed on the other hosts, their anatomy was different: their connections with the vascular system were not developed and there was no transfer of 32P from A. myrtifolia to the parasite. In contrast, the other three host species supported the growth of the parasite and had fully developed haustoria. Effective transfer of 32P from the invasive host to the parasite confirmed this. Our results suggest a range of defence mechanisms in C. pubescens hosts and are consistent with reports of strong detrimental effects on invasive hosts. Further, they amount to evidence for the potential use of a native parasite as biological control for invasive species.

X-ray and cryo-EM structures of inhibitor-bound cytochromebc1complexes for structure-based drug discovery

Cytochromebc1, a dimeric multi-subunit electron-transport protein embedded in the inner mitochondrial membrane, is a major drug target for the treatment and prevention of malaria and toxoplasmosis. Structural studies of cytochromebc1from mammalian homologues co-crystallized with lead compounds have underpinned structure-based drug design to develop compounds with higher potency and selectivity. However, owing to the limited amount of cytochromebc1that may be available from parasites, all efforts have been focused on homologous cytochromebc1complexes from mammalian species, which has resulted in the failure of some drug candidates owing to toxicity in the host. Crystallographic studies of the native parasite proteins are not feasible owing to limited availability of the proteins. Here, it is demonstrated that cytochromebc1is highly amenable to single-particle cryo-EM (which uses significantly less protein) by solving the apo and two inhibitor-bound structures to ∼4.1 Å resolution, revealing clear inhibitor density at the binding site. Therefore, cryo-EM is proposed as a viable alternative method for structure-based drug discovery using both host and parasite enzymes.

A native parasitic plant affects the performance of an introduced host regardless of environmental variation across field sites

Increasing evidence from glasshouse studies shows that native hemiparasitic plants can significantly impact the performance and growth of introduced host plants. We investigated the effect of the native Australian hemiparasite Cassytha pubescens R.Br. on the introduced shrub Ulex europaeus L. at three field sites in South Australia. Parasite infection significantly decreased midday PSII efficiency (ΦPSII) and the maximum electron transport rates (ETRmax) of U. europaeus across sites. The impact of C. pubescens on the photosynthetic performance of U. europaeus may have been caused by infected plants having significantly lower N and K, but higher Fe and Al than uninfected plants at all sites. Significant Al and Fe enrichment in infected plants may be possibly due to the parasite indirectly inducing rhizosphere acidification. At two sites, C. pubescens significantly affected host Fv/Fm, indicating chronic photoinhibition in response to infection. The impact of infection on Fv/Fm was greatest at the wettest site, in line with an experiment where C. pubescens had more impact under high water availability. At this site, infected plants also had the highest foliar Fe and Al. The C isotope (δ13C) of infected plants was significantly lower than that of uninfected plants at only one site. Unusually, the δ13C of the parasite was the same as or significantly higher than that of the hosts. There were no site effects on parasite Fv/Fm or ΦPSII; however, ETRmax and δ13C varied across sites. The results suggest that this native parasite has negative effects on U. europaeus in the field, as was found for glasshouse studies. The abundance of this introduced weed in Australia could be negatively affected by C. pubescens infection.

Consistent patterns of trophic niche specialization in host populations infected with a non-native copepod parasite

SUMMARYPopulations of generalist species often comprise of smaller sub-sets of relatively specialized individuals whose niches comprise small sub-sets of the overall population niche. Here, the role of parasite infections in trophic niche specialization was tested using five wild fish populations infected with the non-native parasite Ergasilus briani, a copepod parasite with a direct lifecycle that infects the gill tissues of fish hosts. Infected and uninfected fishes were sampled from the same habitats during sampling events. Prevalence in the host populations ranged between 16 and 67%, with parasite abundances of up to 66 parasites per fish. Although pathological impacts included hyperplasia and localized haemorrhaging of gill tissues, there were no significant differences in the length, weight and condition of infected and uninfected fishes. Stable isotope analyses (δ13C, δ15N) revealed that the trophic niche of infected fishes, measured as standard ellipse area (i.e. the isotopic niche), was consistently and significantly smaller compared with uninfected conspecifics. These niches of infected fishes always sat within that of uninfected fish, suggesting trophic specialization in hosts. These results suggested trophic specialization is a potentially important non-lethal consequence of parasite infection that results from impaired functional traits of the host.

The high resolution melting analysis (HRM) as a molecular tool for monitoring parasites of the wildlife

SUMMARYIn an interconnected world, the international pet trade on wild animals is becoming increasingly important. As a consequence, non-native parasite species are introduced, which affect the health of wildlife and contribute to the loss of biodiversity. Because the investigation of parasite diversity within vulnerable host species implies the molecular identification of large samples of parasite eggs, the sequencing of DNA barcodes is time-consuming and costly. Thereby, the objectives of our study were to apply the high resolution melting (HRM) approach for species determination from pools of parasite eggs. Molecular assays were validated on flatworm parasites (polystomes) infecting the Mediterranean pond turtleMauremys leprosaand the invasive red-eared sliderTrachemys scripta elegansin French natural environments. HRM analysis results indicated that double or multiple parasitic infections could be detected from wild animal populations. They also showed that the cycle of parasite eggs production was not regular over time and may depend on several factors, among which the ecological niche and the target species. Thereby, monitoring parasites from wild endangered animals implies periodic parasitological surveys to avoid false negative diagnostics, based solely on eggs production.