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Smith BR, Patch KB, Gupta A, Knoles EM, Unckless RL. The genetic basis of variation in immune defense against Lysinibacillus fusiformis infection in Drosophila melanogaster. PLoS Pathog 2023; 19:e1010934. [PMID: 37549163 PMCID: PMC10434897 DOI: 10.1371/journal.ppat.1010934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 08/17/2023] [Accepted: 06/29/2023] [Indexed: 08/09/2023] Open
Abstract
The genetic causes of phenotypic variation often differ depending on the population examined, particularly if the populations were founded by relatively small numbers of genotypes. Similarly, the genetic causes of phenotypic variation among similar traits (resistance to different xenobiotic compounds or pathogens) may also be completely different or only partially overlapping. Differences in genetic causes for variation in the same trait among populations suggests context dependence for how selection acts on those traits. Similarities in the genetic causes of variation for different traits, on the other hand, suggests pleiotropy which would also influence how natural selection shapes variation in a trait. We characterized immune defense against a natural Drosophila pathogen, the Gram-positive bacterium Lysinibacillus fusiformis, in three different populations and found almost no overlap in the genetic architecture of variation in survival post infection. However, when comparing our results to a similar experiment with the fungal pathogen, B. bassiana, we found a convincing shared QTL peak for both pathogens. This peak contains the Bomanin cluster of Drosophila immune effectors. Loss of function mutants and RNAi knockdown experiments confirms a role of some of these genes in immune defense against both pathogens. This suggests that natural selection may act on the entire cluster of Bomanin genes (and the linked region under the QTL) or specific peptides for specific pathogens.
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Affiliation(s)
- Brittny R. Smith
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Kistie B. Patch
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Anjali Gupta
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Emma M. Knoles
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Robert L. Unckless
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
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Narita H, Shima T, Iizuka R, Uemura S. N-terminal region of Drosophila melanogaster Argonaute2 forms amyloid-like aggregates. BMC Biol 2023; 21:78. [PMID: 37072852 PMCID: PMC10114355 DOI: 10.1186/s12915-023-01569-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 03/17/2023] [Indexed: 04/20/2023] Open
Abstract
BACKGROUND Argonaute proteins play a central role in RNA silencing by forming protein-small RNA complexes responsible for the silencing process. While most Argonaute proteins have a short N-terminal region, Argonaute2 in Drosophila melanogaster (DmAgo2) harbors a long and unique N-terminal region. Previous in vitro biochemical studies have shown that the loss of this region does not impair the RNA silencing activity of the complex. However, an N-terminal mutant of Drosophila melanogaster has demonstrated abnormal RNA silencing activity. To explore the causes of this discrepancy between in vitro and in vivo studies, we investigated the biophysical properties of the region. The N-terminal region is highly rich in glutamine and glycine residues, which is a well-known property for prion-like domains, a subclass of amyloid-forming peptides. Therefore, the possibility of the N-terminal region functioning as an amyloid was tested. RESULTS Our in silico and biochemical assays demonstrated that the N-terminal region exhibits amyloid-specific properties. The region indeed formed aggregates that were not dissociated even in the presence of sodium dodecyl sulfate. Also, the aggregates enhanced the fluorescence intensity of thioflavin-T, an amyloid detection reagent. The kinetics of the aggregation followed that of typical amyloid formation exhibiting self-propagating activity. Furthermore, we directly visualized the aggregation process of the N-terminal region under fluorescence microscopy and found that the aggregations took fractal or fibril shapes. Together, the results indicate that the N-terminal region can form amyloid-like aggregates. CONCLUSIONS Many other amyloid-forming peptides have been reported to modulate the function of proteins through their aggregation. Therefore, our findings raise the possibility that aggregation of the N-terminal region regulates the RNA silencing activity of DmAgo2.
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Affiliation(s)
- Haruka Narita
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Tomohiro Shima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
| | - Ryo Iizuka
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Sotaro Uemura
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
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Reddington CJ, Fellner M, Burgess AE, Mace PD. Molecular Regulation of the Polycomb Repressive-Deubiquitinase. Int J Mol Sci 2020; 21:ijms21217837. [PMID: 33105797 PMCID: PMC7660087 DOI: 10.3390/ijms21217837] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/20/2020] [Accepted: 10/20/2020] [Indexed: 12/16/2022] Open
Abstract
Post-translational modification of histone proteins plays a major role in histone–DNA packaging and ultimately gene expression. Attachment of ubiquitin to the C-terminal tail of histone H2A (H2AK119Ub in mammals) is particularly relevant to the repression of gene transcription, and is removed by the Polycomb Repressive-Deubiquitinase (PR-DUB) complex. Here, we outline recent advances in the understanding of PR-DUB regulation, which have come through structural studies of the Drosophila melanogaster PR-DUB, biochemical investigation of the human PR-DUB, and functional studies of proteins that associate with the PR-DUB. In humans, mutations in components of the PR-DUB frequently give rise to malignant mesothelioma, melanomas, and renal cell carcinoma, and increase disease risk from carcinogens. Diverse mechanisms may underlie disruption of the PR-DUB across this spectrum of disease. Comparing and contrasting the PR-DUB in mammals and Drosophila reiterates the importance of H2AK119Ub through evolution, provides clues as to how the PR-DUB is dysregulated in disease, and may enable new treatment approaches in cancers where the PR-DUB is disrupted.
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Brosseau C, Bolaji A, Roussin-Léveillée C, Zhao Z, Biga S, Moffett P. Natural variation in the Arabidopsis AGO2 gene is associated with susceptibility to potato virus X. THE NEW PHYTOLOGIST 2020; 226:866-878. [PMID: 31880814 DOI: 10.1111/nph.16397] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 12/12/2019] [Indexed: 06/10/2023]
Abstract
RNA silencing functions as an anti-viral defence in plants through the action of DICER-like (DCL) and ARGONAUTE (AGO) proteins. Despite the importance of this mechanism, little is known about the functional consequences of variation in genes encoding RNA silencing components. The AGO2 protein has been shown to be important for defense against multiple viruses, and we investigated how naturally occurring differences in AGO2 between and within species affects its antiviral activities. We find that the AGO2 protein from Arabidopsis thaliana, but not Nicotiana benthamiana, effectively limits potato virus X (PVX). Consistent with this, we find that the A. thaliana AGO2 gene shows a high incidence of polymorphisms between accessions, with evidence of selective pressure. Using functional analyses, we identify polymorphisms that specifically affect AGO2 antiviral activity, without interfering with other AGO2-associated functions such as anti-bacterial resistance or DNA methylation. Our results suggest that viruses adapt to overcome RNA silencing in their hosts. Furthermore, they indicate that plant-virus interactions have influenced natural variation in RNA-silencing components and that the latter may be a source of genetically encoded virus resistance.
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Affiliation(s)
- Chantal Brosseau
- Département de Biologie, Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
| | - Ayooluwa Bolaji
- Département de Biologie, Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
| | | | - Zhenxing Zhao
- Département de Biologie, Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
| | - Sébastien Biga
- Département de Biologie, Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
| | - Peter Moffett
- Département de Biologie, Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
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Balasubramanian V, Srinivasan B. Genetic analyses uncover pleiotropic compensatory roles for Drosophila Nucleobindin-1 in inositol trisphosphate-mediated intracellular calcium homeostasis. Genome 2019; 63:61-90. [PMID: 31557446 DOI: 10.1139/gen-2019-0113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nucleobindin-1 is an EF-hand calcium-binding protein with a distinctive profile, predominantly localized to the Golgi in insect and wide-ranging vertebrate cell types, alike. Its putative involvements in intracellular calcium (Ca2+) homeostasis have never been phenotypically characterized in any model organism. We have analyzed an adult-viable mutant that completely disrupts the G protein α-subunit binding and activating (GBA) motif of Drosophila Nucleobindin-1 (dmNUCB1). Such disruption does not manifest any obvious fitness-related, morphological/developmental, or behavioral abnormalities. A single copy of this mutation or the knockdown of dmnucb1 in restricted sets of cells variously rescues pleiotropic mutant phenotypes arising from impaired inositol 1,4,5-trisphosphate receptor (IP3R) activity (in turn depleting cytoplasmic Ca2+ levels across diverse tissue types). Additionally, altered dmNUCB1 expression or function considerably reverses lifespan and mobility improvements effected by IP3R mutants, in a Drosophila model of amyotrophic lateral sclerosis. Homology modeling-based analyses further predict a high degree of conformational conservation in Drosophila, of biochemically validated structural determinants in the GBA motif that specify in vertebrates, the unconventional Ca2+-regulated interaction of NUCB1 with Gαi subunits. The broad implications of our findings are hypothetically discussed, regarding potential roles for NUCB1 in GBA-mediated, Golgi-associated Ca2+ signaling, in health and disease.
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Affiliation(s)
- Vidhya Balasubramanian
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India.,Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India
| | - Bharath Srinivasan
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India.,Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India
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Davis-Vogel C, Van Allen B, Van Hemert JL, Sethi A, Nelson ME, Sashital DG. Identification and comparison of key RNA interference machinery from western corn rootworm, fall armyworm, and southern green stink bug. PLoS One 2018; 13:e0203160. [PMID: 30183751 PMCID: PMC6124762 DOI: 10.1371/journal.pone.0203160] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 08/15/2018] [Indexed: 12/18/2022] Open
Abstract
RNA interference (RNAi)-based technology shows great potential for use in agriculture, particularly for management of costly insect pests. In the decade since the insecticidal effects of environmentally-introduced RNA were first reported, this treatment has been applied to several types of insect pests. Through the course of those efforts, it has become apparent that different insects exhibit a range of sensitivity to environmentally-introduced RNAs. The variation in responses across insect is not well-understood, with differences in the underlying RNAi mechanisms being one explanation. This study evaluates eight proteins among three agricultural pests whose responses to environmental RNAi are known to differ: western corn rootworm (Diabrotica virgifera virgifera), fall armyworm (Spodoptera frugiperda), and southern green stink bug (Nezara viridula). These proteins have been identified in various organisms as centrally involved in facilitating the microRNA- and small interfering-RNA-mediated interference responses. Various bioinformatics tools, as well as gene expression profiling, were used to identify and evaluate putative homologues for characteristics that may contribute to the differing responses of these insects, such as the absence of critical functional domains within expressed sequences, the absence of entire gene sequences, or unusually low or undetectable expression of critical genes. Though many similarities were observed, the number of isoforms and expression levels of double-stranded RNA-binding and argonaute proteins varied across insect. Differences among key RNAi machinery genes of these three pests may impact the function of their RNAi pathways, and therefore, their respective responses to exogenous RNAs.
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Affiliation(s)
- Courtney Davis-Vogel
- Research and Development, DuPont Pioneer, Johnston, Iowa, United States of America
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa, United States of America
| | - Brandon Van Allen
- Research and Development, DuPont Pioneer, Johnston, Iowa, United States of America
| | - John L. Van Hemert
- Research and Development, DuPont Pioneer, Johnston, Iowa, United States of America
| | - Amit Sethi
- Research and Development, DuPont Pioneer, Johnston, Iowa, United States of America
| | - Mark E. Nelson
- Research and Development, DuPont Pioneer, Johnston, Iowa, United States of America
| | - Dipali G. Sashital
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa, United States of America
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Abstract
This review explores the presence and functions of polyglutamine (polyQ) in viral proteins. In mammals, mutations in polyQ segments (and CAG repeats at the nucleotide level) have been linked to neural disorders and ataxias. PolyQ regions in normal human proteins have documented functional roles, in transcription factors and, more recently, in regulating autophagy. Despite the high frequency of polyQ repeats in eukaryotic genomes, little attention has been given to the presence or possible role of polyQ sequences in virus genomes. A survey described here revealed that polyQ repeats occur rarely in RNA viruses, suggesting that they have detrimental effects on virus replication at the nucleotide or protein level. However, there have been sporadic reports of polyQ segments in potyviruses and in reptilian nidoviruses (among the largest RNA viruses known). Conserved polyQ segments are found in the regulatory control proteins of many DNA viruses. Variable length polyQ tracts are found in proteins that contribute to transmissibility (cowpox A-type inclusion protein (ATI)) and control of latency (herpes viruses). New longer-read sequencing methods, using original biological samples, should reveal more details on the presence and functional role of polyQ in viruses, as well as the nucleotide regions that encode them. Given the known toxic effects of polyQ repeats, the role of these segments in neurovirulent and tumorigenic viruses should be further explored.
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Abstract
The power and ease of Drosophila genetics and the medical relevance of mosquito-transmitted viruses have made dipterans important model organisms in antiviral immunology. Studies of virus-host interactions at the molecular and population levels have illuminated determinants of resistance to virus infection. Here, we review the sources and nature of variation in antiviral immunity and virus susceptibility in model dipteran insects, specifically the fruit fly Drosophila melanogaster and vector mosquitoes of the genera Aedes and Culex. We first discuss antiviral immune mechanisms and describe the virus-specificity of these responses. In the following sections, we review genetic and microbiota-dependent variation in antiviral immunity. In the final sections, we explore less well-studied sources of variation, including abiotic factors, sexual dimorphism, infection history, and endogenous viral elements. We borrow from work on other pathogen types and non-dipteran species when it parallels or complements studies in dipterans. Understanding natural variation in virus-host interactions may lead to the identification of novel restriction factors and immune mechanisms and shed light on the molecular determinants of vector competence.
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Affiliation(s)
- William H Palmer
- Institute of Evolutionary Biology and Centre for Infection, Evolution and Immunity, University of Edinburgh, Edinburgh EH9 3FL UK.
| | - Finny S Varghese
- Department of Medical Microbiology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, P.O. Box 9101, Nijmegen 6500 HB, The Netherlands.
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen 6525 GA, The Netherlands.
| | - Ronald P van Rij
- Department of Medical Microbiology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, P.O. Box 9101, Nijmegen 6500 HB, The Netherlands.
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen 6525 GA, The Netherlands.
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Lewis SH, Webster CL, Salmela H, Obbard DJ. Repeated Duplication of Argonaute2 Is Associated with Strong Selection and Testis Specialization in Drosophila. Genetics 2016; 204:757-769. [PMID: 27535930 PMCID: PMC5068860 DOI: 10.1534/genetics.116.192336] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/12/2016] [Indexed: 11/18/2022] Open
Abstract
Argonaute2 (Ago2) is a rapidly evolving nuclease in the Drosophila melanogaster RNA interference (RNAi) pathway that targets viruses and transposable elements in somatic tissues. Here we reconstruct the history of Ago2 duplications across the D. obscura group and use patterns of gene expression to infer new functional specialization. We show that some duplications are old, shared by the entire species group, and that losses may be common, including previously undetected losses in the lineage leading to D. pseudoobscura We find that while the original (syntenic) gene copy has generally retained the ancestral ubiquitous expression pattern, most of the novel Ago2 paralogs have independently specialized to testis-specific expression. Using population genetic analyses, we show that most testis-specific paralogs have significantly lower genetic diversity than the genome-wide average. This suggests recent positive selection in three different species, and model-based analyses provide strong evidence of recent hard selective sweeps in or near four of the six D. pseudoobscura Ago2 paralogs. We speculate that the repeated evolution of testis specificity in obscura group Ago2 genes, combined with their dynamic turnover and strong signatures of adaptive evolution, may be associated with highly derived roles in the suppression of transposable elements or meiotic drive. Our study highlights the lability of RNAi pathways, even within well-studied groups such as Drosophila, and suggests that strong selection may act quickly after duplication in RNAi pathways, potentially giving rise to new and unknown RNAi functions in nonmodel species.
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Affiliation(s)
- Samuel H Lewis
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, EH9 3FL, United Kingdom
| | - Claire L Webster
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, EH9 3FL, United Kingdom
| | - Heli Salmela
- Department of Biosciences, Centre of Excellence in Biological Interactions, University of Helsinki, Finland
| | - Darren J Obbard
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, EH9 3FL, United Kingdom Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, EH9 3FL, United Kingdom
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