Transcriptomics of host-specific interactions in natural populations of the parasitic plant purple witchweed (Striga hermonthica)

Weed Science ◽  
2019 ◽  
Vol 67 (4) ◽  
pp. 397-411 ◽  
Author(s):  
Lua Lopez ◽  
Emily S. Bellis ◽  
Eric Wafula ◽  
Sarah J. Hearne ◽  
Loren Honaas ◽  
...  
Keyword(s):  
Phenotypic Diversity ◽  
Natural Populations ◽  
Allelic Frequency ◽  
Genomic Diversity ◽  
Sub Saharan Africa ◽  
Striga Hermonthica ◽  
Specific Interactions ◽  
Host Parasite Interactions ◽  
Wide Range ◽  
Host Parasite

AbstractHost-specific interactions can maintain genetic and phenotypic diversity in parasites that attack multiple host species. Host diversity, in turn, may promote parasite diversity by selection for genetic divergence or plastic responses to host type. The parasitic weed purple witchweed [Striga hermonthica (Delile) Benth.] causes devastating crop losses in sub-Saharan Africa and is capable of infesting a wide range of grass hosts. Despite some evidence for host adaptation and host-by-Striga genotype interactions, little is known about intraspecific Striga genomic diversity. Here we present a study of transcriptomic diversity in populations of S. hermonthica growing on different hosts (maize [Zea mays L.] vs. grain sorghum [Sorghum bicolor (L.) Moench]). We examined gene expression variation and differences in allelic frequency in expressed genes of aboveground tissues from populations in western Nigeria parasitizing each host. Despite low levels of host-based genome-wide differentiation, we identified a set of parasite transcripts specifically associated with each host. Parasite genes in several different functional categories implicated as important in host–parasite interactions differed in expression level and allele on different hosts, including genes involved in nutrient transport, defense and pathogenesis, and plant hormone response. Overall, we provide a set of candidate transcripts that demonstrate host-specific interactions in vegetative tissues of the emerged parasite S. hermonthica. Our study shows how signals of host-specific processes can be detected aboveground, expanding the focus of host–parasite interactions beyond the haustorial connection.

scholarly journals Host-pathogen coevolution increases genetic variation in susceptibility to infection

2018 ◽  
Author(s):  
Elizabeth ML Duxbury ◽  
Jonathan P Day ◽  
Davide Maria Vespasiani ◽  
Yannik Thüringer ◽  
Ignacio Tolosana ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Variants ◽  
Genetic Architecture ◽  
Natural Populations ◽  
Major Effect ◽  
Cross Infection ◽  
Host Susceptibility ◽  
Susceptibility To Infection ◽  
Host Parasite Interactions ◽  
Host Parasite

AbstractIt is common to find considerable genetic variation in susceptibility to infection in natural populations. We have investigated whether natural selection increases this variation by testing whether host populations show more genetic variation in susceptibility to pathogens that they naturally encounter than novel pathogens. In a large cross-infection experiment involving four species of Drosophila and four host-specific viruses, we always found greater genetic variation in susceptibility to viruses that had coevolved with their host. We went on to examine the genetic architecture of resistance in one host species, finding that there are more major-effect genetic variants in coevolved host-parasite interactions. We conclude that selection by pathogens increases genetic variation in host susceptibility, and much of this effect is caused by the occurrence of major-effect resistance polymorphisms within populations.

scholarly journals Disentangling unspecific and specific transgenerational immune priming components in host-parasite interactions

2018 ◽  
Author(s):  
Frida Ben-Ami ◽  
Christian Orlic ◽  
Roland R. Regoes
Keyword(s):  
Bacterial Pathogen ◽  
Immune Memory ◽  
High Dose ◽  
Immune Priming ◽  
Host Parasite Interactions ◽  
Pasteuria Ramosa ◽  
Wide Range ◽  
Different Strains ◽  
Host Parasite ◽  
First Time

AbstractExposure to a pathogen primes many organisms to respond faster or more efficiently to subsequent exposures. Such priming can be unspecific or specific, and has been found to extend across generations. Disentangling and quantifying specific and unspecific effects is essential for understanding the genetic epidemiology of a system. By combining a large infection experiment and mathematical modeling, we disentangle different transgenerational effects in the crustacean model Daphnia magna exposed to different strains of the bacterial parasite Pasteuria ramosa. In the experiments, we exposed hosts to a high-dose of one of three parasite strains, and subsequently challenged their offspring with multiple doses of the same or a different strain, i. e. homologously or heterogously. We find that exposure to Pasteuria decreases the susceptibility of a host’s offspring by approximately 50%. This transgenerational protection is not larger for homologous than for heterologous parasite challenges. Our work represents an important contribution not only to the analysis of immune priming in ecological systems, but also to the experimental assessment of vaccines. We present for the first time an inference framework to investigate specific and unspecific effects of immune priming on the susceptibility distribution of hosts — effects that are central to understanding immunity and the effect of vaccines.Author summaryImmune memory is a feature of immune systems that forms the basis of vaccination. In opposition to textbook accounts, the ability to specifically remember previous exposures has been found to extend to invertebrates and shown to be able to be passed on from mother to off-spring, i. e. to be transgenerational. In this paper, we investigate the extent of this specificity in unprecedented detail in water fleas. We exposed water flea mothers to different strains of a bacterial pathogen and challenged their offspring with a wide range of doses of a strain that were either identical to (homologous) or different from (heterologous) the strain, to which the mother had been exposed. We find that, while exposure of the mother reduces the susceptibility of the offspring, this effect is not specific. This work outlines the limits of specific transgenerational immune memory in this invertebrate system.

Do parasites matter? Assessing the fitness consequences of haemogregarine infection in snakes

2006 ◽  
Vol 84 (5) ◽  
pp. 668-676 ◽  
Author(s):  
G.P. Brown ◽  
C.M. Shilton ◽  
R. Shine
Keyword(s):  
Evolutionary Ecology ◽  
Natural Populations ◽  
Blood Parasites ◽  
Antipredator Behaviour ◽  
Host Fitness ◽  
Host Parasite Interactions ◽  
Fitness Consequences ◽  
Tropical Australia ◽  
Host Parasite ◽  
Striking Contrast

Although much research in evolutionary ecology is based upon the premise that high levels of parasitism impair the host's functioning, the assumed link between parasitism and fitness has been assessed for relatively few kinds of animals. At our study site in tropical Australia, keelback snakes ( Tropidonophis mairii (Gray, 1841), Colubridae) are heavily infected with haemogregarine blood parasites: 90% of snakes that we tested carried the parasite, with the proportion of erythrocytes containing haemogregarines averaging 15% and ranging up to a remarkable 64%. Prevalence increased with snake body size, but intensity decreased with age. Unlike lizards studied previously, the snakes did not respond to haemogregarine infection by releasing immature erythrocytes into the circulation. In striking contrast to results from a recent study on a sympatric snake species, we did not find any empirical links between parasite numbers and several measures of host fitness (body condition, growth rate, feeding rate, antipredator behaviour, locomotor performance, reproductive status, reproductive output, and recapture rate). The association between this parasite and its host thus appears to be surprisingly benign, suggesting that host–parasite interactions sometimes may have only trivial consequences for host fitness in natural populations. Plausibly, host–parasite coevolution weakens or eliminates fitness costs of parasitism.

Numerical and functional responses of intestinal helminths in three rajid skates: evidence for competition between parasites?

Parasitology ◽  
2012 ◽  
Vol 139 (13) ◽  
pp. 1784-1793 ◽  
Author(s):  
HASEEB S. RANDHAWA
Keyword(s):  
Linear Models ◽  
Niche Breadth ◽  
Specific Interactions ◽  
Intestinal Helminths ◽  
Functional Responses ◽  
Intensity Of Infection ◽  
Host Parasite Interactions ◽  
Niche Shifts ◽  
Host Parasite ◽  
Number Of Individuals

SUMMARYHost-parasite interactions generally involve communities of parasites. Within these communities, species will co-exist and/or interact with one another in a manner either benefiting the species involved or to the detriment of one or more of the species. At the level of helminth infracommunities, evidence for intra- and inter-specific competition includes numerical responses, i.e. those regulating helminth intensity of infection, and functional responses, i.e. where the presence of competitors modifies the realised niche of infrapopulations. The objectives of this study are to assess the numerical and functional responses of helminths in infracommunities from 3 rajid skates using general linear models. Despite a lack of numerical responses, functional responses to intra- and inter-specific interactions were observed. A positive correlation between the number of individuals in an infrapopulation and its niche breadth (functional response) was observed for the tapewormsPseudanthobothriumspp. andEcheneibothriumspp., in all their respective hosts, and for the nematodePseudanisakissp. in the little skate. Evidence for inter-specific competition includes niche shifts inPseudanthobothrium purtoni(exlittle skate) andPseudanisakissp. (exthorny skate) in the presence ofPseudanisakissp. and the tapewormGrillotiasp., respectively. These results are consistent with other studies in providing evidence for competition between helminths of skates.

scholarly journals Identification of candidate virulence loci in Striga hermonthica, a devastating parasite of African cereal crops

2022 ◽  
Author(s):  
Suo Qiu ◽  
James M. Bradley ◽  
Peijun Zhang ◽  
Roy Chaudhuri ◽  
Mark Blaxter ◽  
...  
Keyword(s):  
Host Resistance ◽  
Allelic Variation ◽  
Balancing Selection ◽  
Durable Resistance ◽  
Parasitic Plant ◽  
Sub Saharan Africa ◽  
Striga Hermonthica ◽  
Cell Wall Modification ◽  
A Genome ◽  
Wide Range

Parasites have evolved suites of proteins, Virulence Factors (VFs), that are delivered into host plants to facilitate colonization. Whilst VFs mediating plant-microbe and plant-nematode interactions have been characterised extensively, less is known about VFs mediating parasitic plant interactions with their hosts. Striga hermonthica is an obligate, root-parasitic plant capable of parasitizing multiple cereal hosts in sub-Saharan Africa, causing devastating losses in yields. An understanding of the molecular nature and allelic variation of VFs in S. hermonthica is essential for breeding durable resistance and delaying the evolution of parasite virulence. To address this issue, we assembled a genome for Striga hermonthica and identified candidate VFs by combining in silico prediction of secreted proteins with pooled sequencing of parasites growing on a susceptible and a strongly resistant rice host. Consistent with predictions for parasites, like S. hermonthica, that can interact with multiple hosts, we identified multiple loci, potentially with a wide range of functions, implicated in overcoming host resistance. Extremely different allele frequencies were observed at 152 non-secreted and 38 putatively secreted VFs between S. hermonthica parasitising the resistant and susceptible rice varieties. Our candidate, secreted VFs encompassed functions such as host cell wall modification, protease inhibitors, oxidoreductase and kinase activities, as well as several with unknown functions. Consistent with maintenance of variation at virulence loci by balancing selection the candidate loci had significantly higher Tajima’s D on average than the genomic background. Our results show that diverse strategies are used by  S. hermonthica  to overcome different layers of host resistance. Understanding the maintenance of variation at virulence loci by balancing selection will be critical to managing the evolution of virulence as a part of a sustainable control strategy.

scholarly journals Genomic evidence for population-specific responses to coevolving parasites in a New Zealand freshwater snail

2016 ◽  
Author(s):  
Laura Bankers ◽  
Peter Fields ◽  
Kyle E. McElroy ◽  
Jeffrey L. Boore ◽  
John M. Logsdon ◽  
...  
Keyword(s):  
Natural Populations ◽  
Primary Source ◽  
Population Level ◽  
Freshwater Snail ◽  
Sequence Evolution ◽  
Specific Host ◽  
Host Parasite Interactions ◽  
Evolutionary Trajectories ◽  
Host Parasite ◽  
Genomic Basis

AbstractReciprocal coevolving interactions between hosts and parasites are a primary source of strong selection that can promote rapid and often population- or genotype-specific evolutionary change. These host-parasite interactions are also a major source of disease. Despite their importance, very little is known about the genomic basis of coevolving host-parasite interactions in natural populations, especially in animals. Here, we use gene expression and sequence evolution approaches to take critical steps towards characterizing the genomic basis of interactions between the freshwater snail Potamopyrgus antipodarum and its coevolving sterilizing trematode parasite, Microphallus sp., a textbook example of natural coevolution. We found that Microphallus-infected P. antipodarum exhibit systematic downregulation of genes relative to uninfected P. antipodarum. The specific genes involved in parasite response differ markedly across lakes, consistent with a scenario where population-level coevolution is leading to population-specific host-parasite interactions and evolutionary trajectories. We also used an FST-based approach to identify a set of loci that represent promising candidates for targets of parasite-mediated selection across lakes as well as within each lake population. These results constitute the first genomic evidence for population-specific responses to coevolving infection in the P. antipodarum-Microphallus interaction and provide new insights into the genomic basis of coevolutionary interactions in nature.

scholarly journals Intra- and intersexual differences in parasite resistance and female fitness tolerance in a polymorphic insect

2017 ◽  
Vol 284 (1847) ◽  
pp. 20162407 ◽  
Author(s):  
Beatriz Willink ◽  
Erik I. Svensson
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Natural Populations ◽  
Parasite Resistance ◽  
Water Mite ◽  
Defence Mechanisms ◽  
Ischnura Elegans ◽  
Host Parasite Interactions ◽  
Colour Morphs ◽  
Host Parasite

To understand host–parasite interactions, it is necessary to quantify variation and covariation in defence traits. We quantified parasite resistance and fitness tolerance of a polymorphic damselfly ( Ischnura elegans ), an insect with three discrete female colour morphs but with monomorphic males. We quantified sex and morph differences in parasite resistance (prevalence and intensity of water mite infections) and morph-specific fitness tolerance in the females in natural populations for over a decade. There was no evidence for higher parasite susceptibility in males as a cost of sexual selection, whereas differences in defence mechanisms between female morphs are consistent with correlational selection operating on combinations of parasite resistance and tolerance. We suggest that tolerance differences between female morphs interact with frequency-dependent sexual conflict, which maintains the polymorphism locally. Host–parasite interactions can therefore shape intra- and intersexual phenotypic divergence and interfere with sexual selection and sexual conflict.

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