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Potential for Acanthoscelides obtectus to Adapt to New Hosts Seen in Laboratory Selection Experiments.

ABSTRACT: Effective pest management strategies for a targeted pest species must rely on accurate, reliable and reproducible estimates of population dynamics. Importance of such approaches is even more conspicuous when assessing pest's potential to utilize other stored products. Using an experimental evolution approach, we have focused our attention on a common bean pest, the seed beetle (Acanthoscelides obtectus). We looked into the potential to invade and sustain population growth on two suboptimal host plants (chickpeas and mung beans). Such an approach simulates steps of the host-shift process in storages. By analyzing population dynamics during initial encountering with a new host plant, we detected a population drop for both novel hosts. However, transgenerational development in a novel environment resulted in a constant population growth in chickpeas, but not in mung bean populations. Reversal of chickpea selected populations to original host plant has led to a severe decrease in population parameters due to low viability of immatures, while the opposite trend was detected in mung bean populations. This paper highlights the importance of good practice in estimating population dynamics for economically important species. With special emphasis on storage pest species, we discuss how this approach can be useful for estimating invading potential of pest insects.

SUBMITTER: Savkovic U

PROVIDER: S-EPMC6627625 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Potential for <i>Acanthoscelides obtectus</i> to Adapt to New Hosts Seen in Laboratory Selection Experiments.

Savković Uroš U Đorđević Mirko M Stojković Biljana B

Insects 20190529 6

Effective pest management strategies for a targeted pest species must rely on accurate, reliable and reproducible estimates of population dynamics. Importance of such approaches is even more conspicuous when assessing pest's potential to utilize other stored products. Using an experimental evolution approach, we have focused our attention on a common bean pest, the seed beetle (<i>Acanthoscelides obtectus</i>). We looked into the potential to invade and sustain population growth on two suboptima ...[more]

PMID: 31146407

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Project description:Bacterial pathogens commonly carry prophages that express virulence factors, and human strains of Staphylococcus aureus carry Sa3int phages, which promote immune evasion. Recently, however, these phages have been found in livestock-associated, methicillin-resistant S. aureus (LA-MRSA). This is surprising, as LA-MRSA strains contain a mutated primary bacterial integration site, which likely explains why the rare integration events that do occur mostly happen at alternative locations. Using deep sequencing, we show that after initial integration at secondary sites, Sa3int phages adapt through nucleotide changes in their attachment sequences to increase homology with alternative bacterial attachment sites. Importantly, this homology significantly enhances integrations in new rounds of infections. We propose that promiscuity of the phage-encoded tyrosine recombinase is responsible for establishment of Sa3int phages in LA-MRSA. Our results demonstrate that phages can adopt extensive population heterogeneity, leading to establishment in strains lacking bona fide integration sites. Ultimately, their presence may increase virulence and zoonotic potential of pathogens with major implications for human health. IMPORTANCE A growing number of humans are being infected by antibiotic resistant Staphylococcus aureus originating from livestock. The preference of S. aureus for humans or animals is in part determined by factors encoded by viruses (phages) that reside in the bacterial genome. Here, we reveal a process by which phages adapt to and become integrated in new strains of S. aureus lacking the preferred phage integration site. We propose that this is due to the relaxed specificity of a phage-encoded enzyme called recombinase. As this recombinase is used by many other phages, our results might have implications for a broader range of phages. Importantly, the adaptation described here enables S. aureus to jump between host organisms and increases its zoonotic threat.

Project description:BackgroundThe host specificity and host range of the dry bean beetle, Acanthoscelides obtectus (Coleoptera: Chrysomelidae, Bruchinae), a seed predator of beans, is poorly known. In addition, the female oviposition preference and larval performance relationship is complicated by the respective importance of seed coat and cotyledon, because, paradoxically, females lay eggs on the basis of stimuli of the seed coat alone, without directly being able to assess the quality of the cotyledon's suitability for larval development. Conversely, the thickness of seed coat may prevent first instar larvae from entering the seeds, even if cotyledons are suitable for development.MethodsThe seeds of 62 leguminous species and 75 cultivars and accessions occurring in Hungary were evaluated for preference-performance relations. The preference of female bean beetles for seeds was measured in no-choice egg-laying tests. The ability of first instar larvae to overcome the seed coat as a physical barrier was tested with intact seed coat, while pre-drilled seed coats allowed the larvae to assess the suitability of cotyledon for development. The number of emerging adults was recorded. The thickness of seed coats and the weight of seeds were measured. Nonparametric tests and logistic regression were used for the statistical analyses of data and effect sizes were also calculated.ResultsSeeds of 18 leguminous species (35% of them Lathyrus) supported larval development to adults if the seed coat was pre-drilled; however, only nine leguminous species supported development to adults if the seed coat was intact. Seed coat thickness beyond a critical threshold of 0.1 mm strongly influenced survival of first instar larvae. There was no overall positive correlation between oviposition preference and larval performance, except for 16 so-called acceptable non-hosts (Kendall's τ = 0.3088). A. obtectus females also showed an ovipositional hierarchy of legume species even in no-choice tests.ConclusionsThe results suggest that whereas the use of some acceptable non-host species by the A. obtectus is possible in seed stores, the same is unlikely under outdoor conditions, where the recognition of a diverse set of seed pod-related compounds would be necessary to induce egg-laying.

Project description:BackgroundCommon bean (Phaseolus vulgaris L.) is an important agricultural product with large nutritional value, and the insect pest Acanthoscelides obtectus (Say) seriously affects its product quality and commodity quality during storage. Few researches on genes of bruchid resistance have investigated in common bean cultivars.ResultsIn this study, a bruchid-resistant cultivar black kidney bean and a highly susceptible accession Longyundou3 from different gene banks were crossed to construct a recombinant inbred line population. The genetic analysis indicated a quantitative inheritance of the bruchid resistance trait controlled by polygenes. A high-density genetic map of a total map distance of 1283.68 cM with an average interval of 0.61 cM between each marker was constructed using an F6 population of 157 recombinant inbred lines. The map has 3106 bin markers, containing 2,234,769 SNPs. Using the high-density genetic map, a new quantitative trait locus for the resistance to Acanthoscelides obtectus was identified on chromosome 6. New molecular markers based on the candidate region were developed, and this locus was further delimited to an interval of 122.3 kb between SSR markers I6-4 and I6-16 using an F2 population. This region comprised five genes. Phvul.006G003700, which encodes a bifunctional inhibitor, may be a potential candidate gene for bruchid resistance. Sequencing analysis of candidate gene identified a 5 bp insertion-deletion in promoter of gene Phvul.006G003700 between two parents. Expression analysis of candidate gene revealed that the expression level of Phvul.006G003700 in bruchid-resistant parent was markedly higher than that in bruchid-susceptible parent both in dry seeds and leaves.ConclusionsA high-density genetic linkage map was constructed utilizing whole-genome resequencing and one new QTL for bruchid resistance was identified on chromosome 6 in common bean cultivar. Phvul.006G003700 (encoding a bifunctional inhibitor) may be a potential candidate gene. These results may form the basis for further research to reveal the bruchid resistance molecular mechanism of common bean.

Project description:Many fungal pathogens have short generation times, large population sizes, and mixed reproductive systems, providing high potential to adapt to heterogeneous environments of agroecosystems. Such adaptation complicates disease management and threatens food production. A better understanding of pathogen population biology in such environments is important to reveal key aspects of adaptive divergence processes to allow improved disease management. Here, we studied how evolutionary forces shape population structure of Botrytis cinerea, the causal agent of gray mold, in the Pacific Northwest agroecosystems. Populations of B. cinerea from adjacent fields of small fruit hosts were characterized by combining neutral markers (microsatellites) with markers that directly respond to human-induced selection pressures (fungicide resistance). Populations were diverse, without evidence for recombination and association of pathogen genotype with host. Populations were highly localized with limited migration even among adjacent fields within a farm. A fungicide resistance marker revealed strong selection on population structure due to fungicide use. We found no association of resistance allele with genetic background, suggesting de novo development of fungicide resistance and frequent extinction/recolonization events by different genotypes rather than the spread of resistance alleles among fields via migration of a dominant genotype. Overall our results showed that in agroecosystems, B. cinerea populations respond strongly to selection by fungicide use with greater effect on population structure compared to adaptation to host plant species. This knowledge will be used to improve disease management by developing strategies that limit pathogen local adaptation to fungicides and other human-induced selection pressures present in Pacific Northwest agroecosystems and elsewhere.IMPORTANCE Agroecosystems represent an efficient model for studying fungal adaptation and evolution in anthropogenic environments. In this work, we studied what evolutionary forces shape populations of one of the most important fungal plant pathogens, B. cinerea, in small fruit agroecosystems of the Pacific Northwest. We hypothesized that host, geographic, and anthropogenic factors of agroecosystems structure B. cinerea populations. By combining neutral markers with markers that directly respond to human-induced selection pressures, we show that pathogen populations are highly localized and that selection pressure caused by fungicide use can have a greater effect on population structure than adaptation to host. Our results give a better understanding of population biology and evolution of this important plant pathogen in heterogeneous environments but also provide a practical framework for the development of efficient management strategies by limiting pathogen adaptation to fungicides and other human-induced selection pressures present in agroecosystems of the Pacific Northwest and elsewhere.

Dataset Information

Potential for Acanthoscelides obtectus to Adapt to New Hosts Seen in Laboratory Selection Experiments.

Publications

Potential for <i>Acanthoscelides obtectus</i> to Adapt to New Hosts Seen in Laboratory Selection Experiments.

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