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Vedanayagam J, Lin CJ, Papareddy R, Nodine M, Flynt AS, Wen J, Lai EC. Regulatory logic of endogenous RNAi in silencing de novo genomic conflicts. PLoS Genet 2023; 19:e1010787. [PMID: 37343034 DOI: 10.1371/journal.pgen.1010787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 05/17/2023] [Indexed: 06/23/2023] Open
Abstract
Although the biological utilities of endogenous RNAi (endo-RNAi) have been largely elusive, recent studies reveal its critical role in the non-model fruitfly Drosophila simulans to suppress selfish genes, whose unchecked activities can severely impair spermatogenesis. In particular, hairpin RNA (hpRNA) loci generate endo-siRNAs that suppress evolutionary novel, X-linked, meiotic drive loci. The consequences of deleting even a single hpRNA (Nmy) in males are profound, as such individuals are nearly incapable of siring male progeny. Here, comparative genomic analyses of D. simulans and D. melanogaster mutants of the core RNAi factor dcr-2 reveal a substantially expanded network of recently-emerged hpRNA-target interactions in the former species. The de novo hpRNA regulatory network in D. simulans provides insight into molecular strategies that underlie hpRNA emergence and their potential roles in sex chromosome conflict. In particular, our data support the existence of ongoing rapid evolution of Nmy/Dox-related networks, and recurrent targeting of testis HMG Box loci by hpRNAs. Importantly, the impact of the endo-RNAi network on gene expression flips the convention for regulatory networks, since we observe strong derepression of targets of the youngest hpRNAs, but only mild effects on the targets of the oldest hpRNAs. These data suggest that endo-RNAi are especially critical during incipient stages of intrinsic sex chromosome conflicts, and that continual cycles of distortion and resolution may contribute to speciation.
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Affiliation(s)
- Jeffrey Vedanayagam
- Developmental Biology Program, Sloan Kettering Institute, New York, New York, United States of America
| | - Ching-Jung Lin
- Developmental Biology Program, Sloan Kettering Institute, New York, New York, United States of America
- Weill Graduate School of Medical Sciences, Weill Cornell Medical College, New York, New York, United States of America
| | - Ranjith Papareddy
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Austria
| | - Michael Nodine
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Austria
| | - Alex S Flynt
- Cellular and Molecular Biology, University of Southern Mississippi, Hattiesburg, Mississippi, United States of America
| | - Jiayu Wen
- Division of Genome Sciences and Cancer, The John Curtin School of Medical Research The Australian National University, Canberra, Australia
| | - Eric C Lai
- Developmental Biology Program, Sloan Kettering Institute, New York, New York, United States of America
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Hearn J, Little TJ. Daphnia magna egg piRNA cluster expression profiles change as mothers age. BMC Genomics 2022; 23:429. [PMID: 35672706 PMCID: PMC9175491 DOI: 10.1186/s12864-022-08660-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 05/30/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND PiRNAs prevent transposable elements wreaking havoc on the germline genome. Changes in piRNA expression over the lifetime of an individual may impact on ageing through continued suppression, or release, of transposable element expression. We identified piRNA producing clusters in the genome of Daphnia magna by a combination of bioinformatic methods, and then contrasted their expression between parthenogenetically produced eggs representing maternally-deposited germline piRNAs of young (having their 1st clutch) and old (having their 5th clutch) mothers. Results from eggs were compared to cluster expression in three generations of adults. RESULTS As for other arthropods, D. magna encodes long uni-directionally transcribed non-coding RNAs consisting of fragmented transposable elements which account for most piRNAs expressed. Egg tissues showed extensive differences between clutches from young mothers and those from old mothers, with 578 and 686 piRNA clusters upregulated, respectively. Most log fold-change differences for significant clusters were modest, however. When considering only highly expressed clusters, there was a bias towards 1st clutch eggs at 41 upregulated versus eight clusters in the eggs from older mothers. F0 generation differences between young and old mothers were fewer than eggs, as 179 clusters were up-regulated in young versus 170 old mothers. This dropped to 31 versus 22 piRNA clusters when comparing adults in the F1 generation, and no differences were detected in the F3 generation. Inter-generational losses of differential piRNA cluster were similar to that observed for D. magna micro-RNA expression. CONCLUSIONS Little overlap in differentially expressed clusters was found between adults containing mixed somatic and germline (ovary) tissues and germ-line representing eggs. A cluster encompassing a Tudor domain containing gene important in the piRNA pathway was upregulated in the eggs from old mothers. We hypothesise that regulation of this gene could form part of a feedback loop that reduces piRNA pathway activity explaining the reduced number of highly-expressed clusters in eggs from old mothers.
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Affiliation(s)
- Jack Hearn
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Tom J. Little
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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Almeida MV, Vernaz G, Putman AL, Miska EA. Taming transposable elements in vertebrates: from epigenetic silencing to domestication. Trends Genet 2022; 38:529-553. [DOI: 10.1016/j.tig.2022.02.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 02/14/2022] [Accepted: 02/15/2022] [Indexed: 12/20/2022]
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Lawlor MA, Cao W, Ellison CE. A transposon expression burst accompanies the activation of Y-chromosome fertility genes during Drosophila spermatogenesis. Nat Commun 2021; 12:6854. [PMID: 34824217 PMCID: PMC8617248 DOI: 10.1038/s41467-021-27136-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 11/04/2021] [Indexed: 11/09/2022] Open
Abstract
Transposable elements (TEs) must replicate in germline cells to pass novel insertions to offspring. In Drosophila melanogaster ovaries, TEs can exploit specific developmental windows of opportunity to evade host silencing and increase their copy numbers. However, TE activity and host silencing in the distinct cell types of Drosophila testis are not well understood. Here, we reanalyze publicly available single-cell RNA-seq datasets to quantify TE expression in the distinct cell types of the Drosophila testis. We develop a method for identification of TE and host gene expression modules and find that a distinct population of early spermatocytes expresses a large number of TEs at much higher levels than other germline and somatic components of the testes. This burst of TE expression coincides with the activation of Y chromosome fertility factors and spermatocyte-specific transcriptional regulators, as well as downregulation of many components of the piRNA pathway. The TEs expressed by this cell population are specifically enriched on the Y chromosome and depleted on the X chromosome, relative to other active TEs. These data suggest that some TEs may achieve high insertional activity in males by exploiting a window of opportunity for mobilization created by the activation of spermatocyte-specific and Y chromosome-specific transcriptional programs.
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Affiliation(s)
- Matthew A Lawlor
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ, USA
| | - Weihuan Cao
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ, USA
| | - Christopher E Ellison
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ, USA.
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Kelleher ES. Protein-Protein Interactions Shape Genomic Autoimmunity in the Adaptively Evolving Rhino-Deadlock-Cutoff Complex. Genome Biol Evol 2021; 13:6296839. [PMID: 34115120 PMCID: PMC8290110 DOI: 10.1093/gbe/evab132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2021] [Indexed: 12/23/2022] Open
Abstract
The Piwi-interacting RNA (piRNA) pathway is a genomic defense system that controls the movement of transposable elements (TEs) through transcriptional and post-transcriptional silencing. Although TE defense is critical to ensuring germline genome integrity, it is equally critical that the piRNA pathway avoids autoimmunity in the form of silencing host genes. Ongoing cycles of selection for expanded control of invading TEs, followed by selection for increased specificity to reduce impacts on host genes, are proposed to explain the frequent signatures of adaptive evolution among piRNA pathway proteins. However, empirical tests of this model remain limited, particularly with regards to selection against genomic autoimmunity. I examined three adaptively evolving piRNA proteins, Rhino, Deadlock, and Cutoff, for evidence of interspecific divergence in autoimmunity between Drosophila melanogaster and Drosophila simulans. I tested a key prediction of the autoimmunity hypothesis that foreign heterospecific piRNA proteins will exhibit enhanced autoimmunity, due to the absence of historical selection against off-target effects. Consistent with this prediction, full-length D. simulans Cutoff, as well as the D. simulans hinge and chromo domains of Rhino, exhibit expanded regulation of D. melanogaster genes. I further demonstrate that this autoimmunity is dependent on known incompatibilities between D. simulans proteins or domains and their interacting partners in D. melanogaster. My observations reveal that the same protein–protein interaction domains that are interfaces of adaptive evolution in Rhino and Cutoff also determine their potential for autoimmunity.
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Ellison CE, Kagda MS, Cao W. Telomeric TART elements target the piRNA machinery in Drosophila. PLoS Biol 2020; 18:e3000689. [PMID: 33347429 PMCID: PMC7785250 DOI: 10.1371/journal.pbio.3000689] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 01/05/2021] [Accepted: 12/10/2020] [Indexed: 11/23/2022] Open
Abstract
Coevolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by reestablishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. The TART-A TE functions as an important component of Drosophila telomeres but has also reportedly inserted into the Drosophila melanogaster nuclear export factor gene nxf2. We find that, rather than inserting into nxf2, TART-A has actually captured a portion of nxf2 sequence. We show that TART-A produces abundant Piwi-interacting small RNAs (piRNAs), some of which are antisense to the nxf2 transcript, and that the TART-like region of nxf2 is evolving rapidly. Furthermore, in D. melanogaster, TART-A is present at higher copy numbers, and nxf2 shows reduced expression, compared to the closely related species Drosophila simulans. We propose that capturing nxf2 sequence allowed TART-A to target the nxf2 gene for piRNA-mediated repression and that these 2 elements are engaged in antagonistic coevolution despite the fact that TART-A is serving a critical role for its host genome. Co-evolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by re-establishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. This study shows that a specialized Drosophila retrotransposon that functions as a telomere has captured a portion of a host piRNA gene which may allow it to evade silencing.
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Affiliation(s)
- Christopher E. Ellison
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- * E-mail:
| | - Meenakshi S. Kagda
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Weihuan Cao
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
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Keesey IW, Grabe V, Knaden M, Hansson BS. Divergent sensory investment mirrors potential speciation via niche partitioning across Drosophila. eLife 2020; 9:e57008. [PMID: 32602834 PMCID: PMC7402680 DOI: 10.7554/elife.57008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 06/30/2020] [Indexed: 12/19/2022] Open
Abstract
The examination of phylogenetic and phenotypic characteristics of the nervous system, such as behavior and neuroanatomy, can be utilized as a means to assess speciation. Recent studies have proposed a fundamental tradeoff between two sensory organs, the eye and the antenna. However, the identification of ecological mechanisms for this observed tradeoff have not been firmly established. Our current study examines several monophyletic species within the obscura group, and asserts that despite their close relatedness and overlapping ecology, they deviate strongly in both visual and olfactory investment. We contend that both courtship and microhabitat preferences support the observed inverse variation in these sensory traits. Here, this variation in visual and olfactory investment seems to provide relaxed competition, a process by which similar species can use a shared environment differently and in ways that help them coexist. Moreover, that behavioral separation according to light gradients occurs first, and subsequently, courtship deviations arise.
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Affiliation(s)
- Ian W Keesey
- Max Planck Institute for Chemical Ecology (MPICE), Department of Evolutionary NeuroethologyJenaGermany
| | - Veit Grabe
- Max Planck Institute for Chemical Ecology (MPICE), Department of Evolutionary NeuroethologyJenaGermany
| | - Markus Knaden
- Max Planck Institute for Chemical Ecology (MPICE), Department of Evolutionary NeuroethologyJenaGermany
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology (MPICE), Department of Evolutionary NeuroethologyJenaGermany
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Bachtrog D. The Y Chromosome as a Battleground for Intragenomic Conflict. Trends Genet 2020; 36:510-522. [PMID: 32448494 DOI: 10.1016/j.tig.2020.04.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/17/2020] [Accepted: 04/21/2020] [Indexed: 12/12/2022]
Abstract
Y chromosomes are typically viewed as genetic wastelands with few intact genes. Recent genomic analyses in Drosophila, however, show that gene gain is prominent on young Y chromosomes. Meiosis- and RNAi-related genes often coamplify on recently formed X and Y chromosomes, are testis-expressed, and produce antisense transcripts and short RNAs. RNAi pathways are also involved in suppressing sex ratio drive in Drosophila. These observations paint a dynamic picture of sex chromosome differentiation, suggesting that rapidly evolving genomic battles over segregation are rampant on young sex chromosomes and utilize RNAi to defend the genome against selfish elements that manipulate fair meiosis. Recurrent sex chromosome drive can have profound ecological, evolutionary, and cellular impacts and account for unique features of sex chromosomes.
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Affiliation(s)
- Doris Bachtrog
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA.
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Ellison C, Bachtrog D. Recurrent gene co-amplification on Drosophila X and Y chromosomes. PLoS Genet 2019; 15:e1008251. [PMID: 31329593 PMCID: PMC6690552 DOI: 10.1371/journal.pgen.1008251] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 08/12/2019] [Accepted: 06/18/2019] [Indexed: 12/19/2022] Open
Abstract
Y chromosomes often contain amplified genes which can increase dosage of male fertility genes and counteract degeneration via gene conversion. Here we identify genes with increased copy number on both X and Y chromosomes in various species of Drosophila, a pattern that has previously been associated with sex chromosome drive involving the Slx and Sly gene families in mice. We show that recurrent X/Y co-amplification appears to be an important evolutionary force that has shaped gene content evolution of sex chromosomes in Drosophila. We demonstrate that convergent acquisition and amplification of testis expressed gene families are common on Drosophila sex chromosomes, and especially on recently formed ones, and we carefully characterize one putative novel X/Y co-amplification system. We find that co-amplification of the S-Lap1/GAPsec gene pair on both the X and the Y chromosome occurred independently several times in members of the D. obscura group, where this normally autosomal gene pair is sex-linked due to a sex chromosome-autosome fusion. We explore several evolutionary scenarios that would explain this pattern of co-amplification. Investigation of gene expression and short RNA profiles at the S-Lap1/GAPsec system suggest that, like Slx/Sly in mice, these genes may be remnants of a cryptic sex chromosome drive system, however additional transgenic experiments will be necessary to validate this model. Regardless of whether sex chromosome drive is responsible for this co-amplification, our findings suggest that recurrent gene duplications between X and Y sex chromosomes could have a widespread effect on genomic and evolutionary patterns, including the epigenetic regulation of sex chromosomes, the distribution of sex-biased genes, and the evolution of hybrid sterility.
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Affiliation(s)
- Christopher Ellison
- Department of Integrative Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Doris Bachtrog
- Department of Integrative Biology, University of California Berkeley, Berkeley, California, United States of America
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