RESUMEN
The germline mobilization of transposable elements (TEs) by small RNA mediated silencing pathways is conserved across eukaryotes and critical for ensuring the integrity of gamete genomes. However, genomes are recurrently invaded by novel TEs through horizontal transfer. These invading TEs are not targeted by host small RNAs, and their unregulated activity can cause DNA damage in germline cells and ultimately lead to sterility. Here we use hybrid dysgenesis-a sterility syndrome of Drosophila caused by transposition of invading P-element DNA transposons-to uncover host genetic variants that modulate dysgenic sterility. Using a panel of highly recombinant inbred lines of Drosophila melanogaster, we identified two linked quantitative trait loci (QTL) that determine the severity of dysgenic sterility in young and old females, respectively. We show that ovaries of fertile genotypes exhibit increased expression of splicing factors that suppress the production of transposase encoding transcripts, which likely reduces the transposition rate and associated DNA damage. We also show that fertile alleles are associated with decreased sensitivity to double-stranded breaks and enhanced DNA repair, explaining their ability to withstand high germline transposition rates. Together, our work reveals a diversity of mechanisms whereby host genotype modulates the cost of an invading TE, and points to genetic variants that were likely beneficial during the P-element invasion.
Asunto(s)
Drosophila melanogaster , Infertilidad , Animales , Femenino , Drosophila melanogaster/genética , Empalme Alternativo , Drosophila/genética , Elementos Transponibles de ADN , Reparación del ADN , Variación Genética , Infertilidad/genéticaRESUMEN
Transposable elements (TEs) are mobile genetic parasites that can exponentially increase their genomic abundance through self-propagation. Classic theoretical papers highlighted the importance of two potentially escalating forces that oppose TE spread: regulated transposition and purifying selection. Here, we review new insights into mechanisms of TE regulation and purifying selection, which reveal the remarkable foresight of these theoretical models. We further highlight emergent connections between transcriptional control enacted by small RNAs and the contribution of TE insertions to structural mutation and host-gene regulation. Finally, we call for increased comparative analysis of TE dynamics and fitness effects, as well as host control mechanisms, to reveal how interconnected forces shape the differential prevalence and distribution of TEs across the tree of life.
Asunto(s)
Elementos Transponibles de ADN/genética , Evolución Molecular , Modelos Genéticos , Selección Genética , Animales , Humanos , Interferencia de ARNRESUMEN
The regulation of transposable element (TE) activity by small RNAs is a ubiquitous feature of germlines. However, despite the obvious benefits to the host in terms of ensuring the production of viable gametes and maintaining the integrity of the genomes they carry, it remains controversial whether TE regulation evolves adaptively. We examined the emergence and evolutionary dynamics of repressor alleles after P-elements invaded the Drosophila melanogaster genome in the mid-twentieth century. In many animals including Drosophila, repressor alleles are produced by transpositional insertions into piRNA clusters, genomic regions encoding the Piwi-interacting RNAs (piRNAs) that regulate TEs. We discovered that â¼94% of recently collected isofemale lines in the Drosophila melanogaster Genetic Reference Panel (DGRP) contain at least one P-element insertion in a piRNA cluster, indicating that repressor alleles are produced by de novo insertion at an exceptional rate. Furthermore, in our sample of approximately 200 genomes, we uncovered no fewer than 80 unique P-element insertion alleles in at least 15 different piRNA clusters. Finally, we observe no footprint of positive selection on P-element insertions in piRNA clusters, suggesting that the rapid evolution of piRNA-mediated repression in D. melanogaster was driven primarily by mutation. Our results reveal for the first time how the unique genetic architecture of piRNA production, in which numerous piRNA clusters can encode regulatory small RNAs upon transpositional insertion, facilitates the nonadaptive rapid evolution of repression.
Asunto(s)
Elementos Transponibles de ADN , Silenciador del Gen , Mutación , Interferencia de ARN , ARN Interferente Pequeño/genética , Alelos , Animales , Drosophila melanogaster/genética , Evolución Molecular , Frecuencia de los Genes , Genoma de los Insectos , Genómica/métodos , Familia de Multigenes , Selección GenéticaRESUMEN
In metazoan germlines, the piRNA pathway acts as a genomic immune system, employing small RNA-mediated silencing to defend host DNA from the harmful effects of transposable elements (TEs). Expression of genomic TEs is proposed to initiate self regulation by increasing the production of repressive piRNAs, thereby "adapting" piRNA-mediated control to the most active TE families. Surprisingly, however, piRNA pathway proteins, which execute piRNA biogenesis and enforce silencing of targeted sequences, evolve rapidly and adaptively in animals. If TE silencing is ensured through piRNA biogenesis, what necessitates changes in piRNA pathway proteins? Here we used interspecific complementation to test for functional differences between Drosophila melanogaster and D. simulans alleles of three adaptively evolving piRNA pathway proteins: Armitage, Aubergine and Spindle-E. In contrast to piRNA-mediated transcriptional regulators examined in previous studies, these three proteins have cytoplasmic functions in piRNA maturation and post-transcriptional silencing. Across all three proteins we observed interspecific divergence in the regulation of only a handful of TE families, which were more robustly silenced by the heterospecific piRNA pathway protein. This unexpected result suggests that unlike transcriptional regulators, positive selection has not acted on cytoplasmic piRNA effector proteins to enhance their function in TE repression. Rather, TEs may evolve to "escape" silencing by host proteins. We further discovered that D. simulans alleles of aub and armi exhibit enhanced off-target effects on host transcripts in a D. melanogaster background, as well as modest reductions in the efficiency of piRNA biogenesis, suggesting that promiscuous binding of D. simulans Aub and Armi proteins to host transcripts reduces their participation in piRNA production. Avoidance of genomic auto-immunity may therefore be a critical target of selection. Our observations suggest that piRNA effector proteins are subject to an evolutionary trade-off between defending the host genome from the harmful effect of TEs while also minimizing collateral damage to host genes.
Asunto(s)
Autoinmunidad/genética , Elementos Transponibles de ADN/inmunología , Drosophila simulans/genética , Evolución Molecular , Genoma de los Insectos/inmunología , ARN Interferente Pequeño/biosíntesis , Alelos , Animales , Animales Modificados Genéticamente , Citoplasma/genética , Citoplasma/metabolismo , Elementos Transponibles de ADN/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/inmunología , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/inmunología , Drosophila melanogaster/metabolismo , Drosophila simulans/metabolismo , Femenino , Regulación de la Expresión Génica/inmunología , Genoma de los Insectos/genética , Masculino , Mutación , Interferencia de ARN/inmunologíaRESUMEN
Transposable elements (TEs) are obligate genetic parasites that propagate in host genomes by replicating in germline nuclei, thereby ensuring transmission to offspring. This selfish replication not only produces deleterious mutations-in extreme cases, TE mobilization induces genotoxic stress that prohibits the production of viable gametes. Host genomes could reduce these fitness effects in two ways: resistance and tolerance. Resistance to TE propagation is enacted by germline-specific small-RNA-mediated silencing pathways, such as the Piwi-interacting RNA (piRNA) pathway, and is studied extensively. However, it remains entirely unknown whether host genomes may also evolve tolerance by desensitizing gametogenesis to the harmful effects of TEs. In part, the absence of research on tolerance reflects a lack of opportunity, as small-RNA-mediated silencing evolves rapidly after a new TE invades, thereby masking existing variation in tolerance. We have exploited the recent historical invasion of the Drosophila melanogaster genome by P-element DNA transposons in order to study tolerance of TE activity. In the absence of piRNA-mediated silencing, the genotoxic stress imposed by P-elements disrupts oogenesis and, in extreme cases, leads to atrophied ovaries that completely lack germline cells. By performing quantitative trait locus (QTL) mapping on a panel of recombinant inbred lines (RILs) that lack piRNA-mediated silencing of P-elements, we uncovered multiple QTL that are associated with differences in tolerance of oogenesis to P-element transposition. We localized the most significant QTL to a small 230-kb euchromatic region, with the logarithm of the odds (LOD) peak occurring in the bruno locus, which codes for a critical and well-studied developmental regulator of oogenesis. Genetic, cytological, and expression analyses suggest that bruno dosage modulates germline stem cell (GSC) loss in the presence of P-element activity. Our observations reveal segregating variation in TE tolerance for the first time, and implicate gametogenic regulators as a source of tolerant variants in natural populations.
Asunto(s)
Adaptación Biológica/genética , Elementos Transponibles de ADN/genética , Proteínas de Drosophila/fisiología , Proteínas de Unión al ARN/fisiología , Animales , Evolución Biológica , Mapeo Cromosómico , Elementos Transponibles de ADN/fisiología , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Evolución Molecular , Femenino , Silenciador del Gen/fisiología , Variación Genética/genética , Genoma de los Insectos , Células Germinativas , Oogénesis/genética , Ovario/fisiología , Sitios de Carácter Cuantitativo/genética , Interferencia de ARN , ARN Interferente Pequeño/genéticaRESUMEN
Hybrid dysgenesis is a sterility syndrome resulting from the mobilization of certain transposable elements in the Drosophila germline. Particularly extreme is the hybrid dysgenesis syndrome caused by P-element DNA transposons, in which dysgenic female ovaries often contain few or no germline cells. Those offspring that are produced from dysgenic germlines exhibit high rates of de novo mutation and recombination, implicating transposition-associated DNA damage as the cause of germline loss. However, how this loss occurs, in terms of the particular cellular response that is triggered (cell cycle arrest, senescence, or cell death) remains poorly understood. We demonstrate that two components of the DNA damage response, Checkpoint kinase 2 and its downstream target p53, determine the frequency of ovarian atrophy that is associated with P-element hybrid dysgenesis. We further show that p53 is strongly induced in the germline stem cells (GSCs) of dysgenic females, and is required for their maintenance. Our observations support the critical role for p53 in conferring tolerance of transposable element activity in stem cells.
Asunto(s)
Puntos de Control del Ciclo Celular , Senescencia Celular , Daño del ADN , Elementos Transponibles de ADN , Proteínas de Drosophila/metabolismo , Células Germinativas/metabolismo , Mutación , Proteína p53 Supresora de Tumor/metabolismo , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Femenino , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Marfan syndrome (MS) is a connective tissue disorder that affects thousands of adolescents [Population Reference Bureau, 2013]. Some adolescent patients with MS may use social media to express their experiences and emotions, but little is known about what patients choose to share online. To investigate social media content related to Marfan syndrome we used search terms "Marfan syndrome" and "Marfans" on six different social media sites. The top five recent and popular posts for each site were collected and coded weekly for five weeks. Posts were excluded if they were reshared content or not in English. A codebook was developed using an iterative process to categorize posts and comments. Out of 300 posts collected 147 posts (49.0%) were included for evaluation. Categories of displayed content included personal pictures, memes and pictures featuring symptoms of MS (41.5%) and personal MS experiences (27.1% of posts). One quarter of the posts specifically mentioned a positive experience or how thankful the profile owner was for their life. A unique category of posts (13.7%) referenced Austin Carlile, a celebrity singer with MS, as a role model. Physicians and healthcare providers may consider using social media to understand common MS concerns and to place future health education materials.
Asunto(s)
Síndrome de Marfan/psicología , Medios de Comunicación Sociales , HumanosRESUMEN
The Piwi-interacting RNA (piRNA) pathway defends the germline of animals from the deleterious activity of selfish transposable elements (TEs) through small-RNA mediated silencing. Adaptation to novel invasive TEs is proposed to occur by incorporating their sequences into the piRNA pool that females produce and deposit into their eggs, which then propagates immunity against specific TEs to future generations. In support of this model, the F1 offspring of crosses between strains of the same Drosophila species sometimes suffer from germline derepression of paternally inherited TE families, caused by a failure of the maternal strain to produce the piRNAs necessary for their regulation. However, many protein components of the Drosophila piRNA pathway exhibit signatures of positive selection, suggesting that they also contribute to the evolution of host genome defense. Here we investigate piRNA pathway function and TE regulation in the F1 hybrids of interspecific crosses between D. melanogaster and D. simulans and compare them with intraspecific control crosses of D. melanogaster. We confirm previous reports showing that intraspecific crosses are characterized by derepression of paternally inherited TE families that are rare or absent from the maternal genome and piRNA pool, consistent with the role of maternally deposited piRNAs in shaping TE silencing. In contrast to the intraspecific cross, we discover that interspecific hybrids are characterized by widespread derepression of both maternally and paternally inherited TE families. Furthermore, the pattern of derepression of TE families in interspecific hybrids cannot be attributed to their paucity or absence from the piRNA pool of the maternal species. Rather, we demonstrate that interspecific hybrids closely resemble piRNA effector-protein mutants in both TE misregulation and aberrant piRNA production. We suggest that TE derepression in interspecific hybrids largely reflects adaptive divergence of piRNA pathway genes rather than species-specific differences in TE-derived piRNAs.
Asunto(s)
Drosophila/genética , Hibridación Genética , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Adaptación Biológica , Animales , Animales Modificados Genéticamente/genética , Animales Modificados Genéticamente/metabolismo , Proteínas Argonautas/genética , Proteínas Argonautas/metabolismo , Cruzamientos Genéticos , Elementos Transponibles de ADN , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Evolución Molecular , Femenino , Prueba de Complementación Genética , Genoma de los Insectos , Inmunohistoquímica , Patrón de Herencia , Masculino , Mutación , Ovario/citología , Ovario/metabolismo , Factores de Iniciación de Péptidos/genética , Factores de Iniciación de Péptidos/metabolismo , Fenotipo , ARN Interferente Pequeño/genética , Selección Genética , Especificidad de la EspecieRESUMEN
The Piwi-interacting RNA (piRNA) pathway defends animal genomes against the harmful consequences of transposable element (TE) infection by imposing small-RNA-mediated silencing. Because silencing is targeted by TE-derived piRNAs, piRNA production is posited to be central to the evolution of genome defense. We harnessed genomic data sets from Drosophila melanogaster, including genome-wide measures of piRNA, mRNA, and genomic abundance, along with estimates of age structure and risk of ectopic recombination, to address fundamental questions about the functional and evolutionary relationships between TE families and their regulatory piRNAs. We demonstrate that mRNA transcript abundance, robustness of "ping-pong" amplification, and representation in piRNA clusters together explain the majority of variation in piRNA abundance between TE families, providing the first robust statistical support for the prevailing model of piRNA biogenesis. Intriguingly, we also discover that the most transpositionally active TE families, with the greatest capacity to induce harmful mutations or disrupt gametogenesis, are not necessarily the most abundant among piRNAs. Rather, the level of piRNA targeting is largely independent of recent transposition rate for active TE families, but is rapidly lost for inactive TEs. These observations are consistent with population genetic theory that suggests a limited selective advantage for host repression of transposition. Additionally, we find no evidence that piRNA targeting responds to selection against a second major cost of TE infection: ectopic recombination between TE insertions. Our observations confirm the pivotal role of piRNA-mediated silencing in defending the genome against selfish transposition, yet also suggest limits to the optimization of host genome defense.
Asunto(s)
Elementos Transponibles de ADN/genética , Drosophila melanogaster/genética , Evolución Molecular , Silenciador del Gen , Genoma de los Insectos , ARN Interferente Pequeño/genética , Animales , Amplificación de Genes , Dosificación de Gen , Familia de Multigenes , Recombinación Genética , Selección Genética , Transcripción GenéticaRESUMEN
In internally fertilizing organisms, mating involves a series of highly coordinated molecular interactions between the sexes that occur within the female reproductive tract. In species where females mate multiply, traits involved in postcopulatory interactions are expected to evolve rapidly, potentially leading to postmating-prezygotic (PMPZ) reproductive isolation between diverging populations. Here, we investigate the postmating transcriptional response of the lower reproductive tract of Drosophila mojavensis females following copulation with either conspecific or heterospecific (Drosophila arizonae) males at three time points postmating. Relatively few genes (15 total) were differentially regulated in the female lower reproductive tract in response to conspecific mating. Heterospecifically mated females exhibited significant perturbations in the expression of the majority of these genes, and also down-regulated transcription of a number of others, including several involved in mitochondrial function. These striking regulatory differences indicate failed postcopulatory molecular interactions between the sexes consistent with the strong PMPZ isolation observed for this cross. We also report the transfer of male accessory-gland protein (Acp) transcripts from males to females during copulation, a finding with potentially broad implications for understanding postcopulatory molecular interactions between the sexes.
Asunto(s)
Drosophila/genética , Drosophila/fisiología , Animales , Secuencia de Bases , Copulación/fisiología , Cartilla de ADN/genética , Proteínas de Drosophila/genética , Evolución Molecular , Femenino , Perfilación de la Expresión Génica , Genitales Femeninos/fisiología , Genitales Masculinos/fisiología , Masculino , Preferencia en el Apareamiento Animal/fisiología , Datos de Secuencia Molecular , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Especificidad de la Especie , Transcripción GenéticaRESUMEN
To understand the T cell response to prostate cancer, we created transgenic mice that express a model antigen in a prostate-restricted pattern and crossed these animals to TRAMP mice that develop spontaneous prostate cancer. Adoptive transfer of prostate-specific CD4 T cells shows that, in the absence of prostate cancer, the prostate gland is mostly ignored. Tumorigenesis allows T cell recognition of the prostate gland--but this recognition is tolerogenic, resulting in abortive proliferation and ultimately in hyporesponsiveness at the systemic level. Androgen ablation (the most common treatment for metastatic prostate cancer) was able to mitigate this tolerance--allowing prostate-specific T cells to expand and develop effector function after vaccination. These results suggest that immunotherapy for prostate cancer may be most efficacious when administered after androgen ablation.
Asunto(s)
Andrógenos/metabolismo , Antígenos Virales de Tumores/inmunología , Próstata/metabolismo , Neoplasias de la Próstata/inmunología , Traslado Adoptivo , Animales , Linfocitos T CD4-Positivos/inmunología , Humanos , Masculino , Ratones , Ratones Endogámicos , Ratones Transgénicos , Orquiectomía , Próstata/citología , Próstata/patología , Neoplasias de la Próstata/patologíaRESUMEN
Transposable elements (TEs) are obligate genomic parasites, relying on host germline cells to ensure their replication and passage to future generations. While some TEs exhibit high fidelity to their host genome, being passed from parent to offspring through vertical transmission for millions of years, others frequently invade new and distantly related hosts through horizontal transfer. In this review, I highlight how the complexity of interactions between TE and host required for transposition may be an important determinant of horizontal transfer: with TEs with more complex regulatory requirements being less able to invade new host genomes.
Asunto(s)
Elementos Transponibles de ADN , Evolución Molecular , Elementos Transponibles de ADN/genética , Transferencia de Gen Horizontal/genética , GenómicaRESUMEN
Transposable elements (TEs) are mobile genetic parasites that frequently invade new host genomes through horizontal transfer. Invading TEs often exhibit a burst of transposition, followed by reduced transposition rates as repression evolves in the host. We recreated the horizontal transfer of P-element DNA transposons into a Drosophila melanogaster host and followed the expansion of TE copies and evolution of host repression in replicate laboratory populations reared at different temperatures. We observed that while populations maintained at high temperatures rapidly go extinct after TE invasion, those maintained at lower temperatures persist, allowing for TE spread and the evolution of host repression. We also surprisingly discovered that invaded populations experienced recurrent insertion of P-elements into a specific long non-coding RNA, lncRNA:CR43651, and that these insertion alleles are segregating at unusually high frequency in experimental populations, indicative of positive selection. We propose that, in addition to driving the evolution of repression, transpositional bursts of invading TEs can drive molecular adaptation.
Asunto(s)
Drosophila melanogaster , Evolución Molecular , Animales , Drosophila melanogaster/genética , ARN Interferente Pequeño/genética , Elementos Transponibles de ADN , AclimataciónRESUMEN
A major focus of cancer immunotherapy is to develop strategies to induce T-cell responses through presentation of tumor antigens by dendritic cells (DCs). Current vaccines are limited in their ability to efficiently transfer antigens to DCs in vivo. Ex vivo-generated DCs can be efficiently loaded with antigen but after reinjection, few DCs traffic to secondary lymphoid organs, the critical sites for antigen presentation. To enhance efficiency and durability of antigen presentation by DCs, we transduced hematopoietic stem-progenitor cells (HSCs) with a model tumor antigen and then transplanted the gene-modified cells into irradiated recipient mice, which resulted in efficient expression of the transgene in a large proportion of donor derived DCs in lymphoid organs. The combination of bone marrow transplantation (BMT) using transduced HSCs, systemic agents that generate and activate DCs, and mature T-cell infusion resulted in substantial expansion and activation of antigen-specific T cells. This tripartite strategy provided potent antigen-specific immunotherapy for an aggressive established tumor.
Asunto(s)
Trasplante de Médula Ósea/métodos , Trasplante de Células Madre Hematopoyéticas/métodos , Inmunoterapia Adoptiva/métodos , Linfoma de Células B/inmunología , Linfoma de Células B/terapia , Neoplasias Experimentales/inmunología , Neoplasias Experimentales/terapia , Animales , Antígenos/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Antígenos CD40/genética , Antígenos CD40/inmunología , Antígenos CD40/metabolismo , Linfocitos T CD8-positivos/fisiología , Células Cultivadas , Células Dendríticas/fisiología , Hemaglutinación/genética , Células Madre Hematopoyéticas/fisiología , Interferón gamma/metabolismo , Lentivirus/genética , Linfoma de Células B/genética , Ratones , Ratones Endogámicos BALB C , Neoplasias Experimentales/genética , Bazo/citología , Tasa de Supervivencia , Linfocitos T/inmunología , Linfocitos T/fisiología , Transducción Genética , Trasplante AutólogoRESUMEN
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.
Asunto(s)
Proteínas de Drosophila , Drosophila melanogaster , Animales , Autoinmunidad/genética , Elementos Transponibles de ADN/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Drosophila simulans/genética , Genómica , ARN Interferente Pequeño/genéticaRESUMEN
Long-term photophobia in children that has no obvious cause is uncommon and presents a diagnostic dilemma. It may produce significant discomfort and result in social isolation and school absence. We present the case of a 5-year-old boy who presented with chronic photophobia due to interstitial keratitis that was the result of Lyme disease.
Asunto(s)
Queratitis , Enfermedad de Lyme , Niño , Preescolar , Humanos , Queratitis/diagnóstico , Enfermedad de Lyme/complicaciones , Enfermedad de Lyme/diagnóstico , Enfermedad de Lyme/tratamiento farmacológico , Masculino , Fotofobia/diagnóstico , Fotofobia/etiologíaRESUMEN
Secreted proteases play integral roles in sexual reproduction in a broad range of taxa. In the genetic model Drosophila melanogaster, these molecules are thought to process peptides and activate enzymes inside female reproductive tracts, mediating critical postmating responses. A recent study of female reproductive tract proteins in the cactophilic fruit fly Drosophila arizonae, identified pervasive, lineage-specific gene duplication amongst secreted proteases. Here, we compare the evolutionary dynamics, biochemical nature, and physiological significance of secreted female reproductive serine endoproteases between D. arizonae and its congener D. melanogaster. We show that D. arizonae lower female reproductive tract (LFRT) proteins are significantly enriched for recently duplicated secreted proteases, particularly serine endoproteases, relative to D. melanogaster. Isolated lumen from D. arizonae LFRTs, furthermore, exhibits significant trypsin-like and elastase-like serine endoprotease activity, whereas no such activity is seen in D. melanogaster. Finally, trypsin- and elastase-like activity in D. arizonae female reproductive tracts is negatively regulated by mating. We propose that the intense proteolytic environment of the D. arizonae female reproductive tract relates to the extraordinary reproductive physiology of this species and that ongoing gene duplication amongst these proteases is an evolutionary consequence of sexual conflict.
Asunto(s)
Drosophila/enzimología , Drosophila/genética , Duplicación de Gen , Genitales Femeninos/enzimología , Procesamiento Proteico-Postraduccional/genética , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Animales , Sistema Digestivo/enzimología , Drosophila melanogaster/enzimología , Drosophila melanogaster/genética , Evolución Molecular , Femenino , Elastasa Pancreática/genética , Elastasa Pancreática/metabolismo , Reproducción , Tripsina/genética , Tripsina/metabolismoRESUMEN
Protein components of the Drosophila male ejaculate, several of which evolve rapidly, are critical modulators of reproductive success. Recent studies of female reproductive tract proteins indicate they also are extremely divergent between species, suggesting that reproductive molecules may coevolve between the sexes. Our current understanding of intersexual coevolution, however, is severely limited by the paucity of genetic and evolutionary studies on the female molecules involved. Physiological evidence of ejaculate-female coadaptation, paired with a promiscuous mating system, makes Drosophila mojavensis an exciting model system in which to study the evolution of reproductive proteins. Here we explore the evolutionary dynamics of a five-paralog gene family of female reproductive proteases within populations of D. mojavensis and throughout the repleta species group. We show that the proteins have experienced ongoing gene duplication and adaptive evolution and further exhibit dynamic patterns of pseudogenation, copy number variation, gene conversion, and selection within geographically isolated populations of D. mojavensis. The integration of these patterns in a single gene family has never before been documented in a reproductive protein.
Asunto(s)
Drosophila/genética , Conversión Génica , Duplicación de Gen , Reproducción/genética , Selección Genética , Animales , Arizona , California , Clima Desértico , Proteínas de Drosophila/genética , Femenino , Genes de Insecto , Masculino , Modelos Moleculares , Filogenia , Recombinación GenéticaRESUMEN
It frequently has been postulated that intersexual coevolution between the male ejaculate and the female reproductive tract is a driving force in the rapid evolution of reproductive proteins. The dearth of research on female tracts, however, presents a major obstacle to empirical tests of this hypothesis. Here, we employ a comparative EST approach to identify 241 candidate female reproductive proteins in Drosophila arizonae, a repleta group species in which physiological ejaculate-female coevolution has been documented. Thirty-one of these proteins exhibit elevated amino acid substitution rates, making them candidates for molecular coevolution with the male ejaculate. Strikingly, we also discovered 12 unique digestive proteases whose expression is specific to the D. arizonae lower female reproductive tract. These enzymes belong to classes most commonly found in the gastrointestinal tracts of a diverse array of organisms. We show that these proteases are associated with recent, lineage-specific gene duplications in the Drosophila repleta species group, and exhibit strong signatures of positive selection. Observation of adaptive evolution in several female reproductive tract proteins indicates they are active players in the evolution of reproductive tract interactions. Additionally, pervasive gene duplication, adaptive evolution, and rapid acquisition of a novel digestive function by the female reproductive tract points to a novel coevolutionary mechanism of ejaculate-female interaction.