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1.
Nat Commun ; 12(1): 1019, 2021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-33589637

RESUMO

Genome-wide variation in introgression rates across hybrid zones offers a powerful opportunity for studying population differentiation. One poorly understood pattern of introgression is the geographic displacement of a trait implicated in lineage divergence from genome-wide population boundaries. While difficult to interpret, this pattern can facilitate the dissection of trait genetic architecture because traits become uncoupled from their ancestral genomic background. We studied an example of trait displacement generated by the introgression of head plumage coloration from personata to alba subspecies of the white wagtail. A previous study of their hybrid zone in Siberia revealed that the geographic transition in this sexual signal that mediates assortative mating was offset from other traits and genetic markers. Here we show that head plumage is associated with two small genetic regions. Despite having a simple genetic architecture, head plumage inheritance is consistent with partial dominance and epistasis, which could contribute to its asymmetric introgression.


Assuntos
Introgressão Genética , Genoma , Passeriformes/genética , Pigmentação/genética , Característica Quantitativa Herdável , Animais , Quimera , Cor , Epistasia Genética , Plumas/anatomia & histologia , Plumas/metabolismo , Feminino , Masculino , Passeriformes/anatomia & histologia , Passeriformes/classificação , Sibéria , Uzbequistão
2.
Nat Commun ; 12(1): 803, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547285

RESUMO

Meiotic recombination is a critical process for plant breeding, as it creates novel allele combinations that can be exploited for crop improvement. In wheat, a complex allohexaploid that has a diploid-like behaviour, meiotic recombination between homoeologous or alien chromosomes is suppressed through the action of several loci. Here, we report positional cloning of Pairing homoeologous 2 (Ph2) and functional validation of the wheat DNA mismatch repair protein MSH7-3D as a key inhibitor of homoeologous recombination, thus solving a half-century-old question. Similar to ph2 mutant phenotype, we show that mutating MSH7-3D induces a substantial increase in homoeologous recombination (up to 5.5 fold) in wheat-wild relative hybrids, which is also associated with a reduction in homologous recombination. These data reveal a role for MSH7-3D in meiotic stabilisation of allopolyploidy and provides an opportunity to improve wheat's genetic diversity through alien gene introgression, a major bottleneck facing crop improvement.


Assuntos
DNA de Plantas/genética , Regulação da Expressão Gênica de Plantas , Recombinação Homóloga , Melhoramento Vegetal/métodos , Proteínas de Plantas/genética , Triticum/genética , Alelos , Quimera , Cromossomos de Plantas/química , Reparo de Erro de Pareamento de DNA , DNA de Plantas/metabolismo , Meiose , Mutação , Mapeamento Físico do Cromossomo , Proteínas de Plantas/metabolismo , Ploidias , Secale/genética , Secale/metabolismo , Triticum/metabolismo
3.
Sci Rep ; 11(1): 2636, 2021 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-33514761

RESUMO

DNA synthesis in vitro has enabled the rapid production of reference standards. These are used as controls, and allow measurement and improvement of the accuracy and quality of diagnostic tests. Current reference standards typically represent target genetic material, and act only as positive controls to assess test sensitivity. However, negative controls are also required to evaluate test specificity. Using a pair of chimeric A/B RNA standards, this allowed incorporation of positive and negative controls into diagnostic testing for the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). The chimeric standards constituted target regions for RT-PCR primer/probe sets that are joined in tandem across two separate synthetic molecules. Accordingly, a target region that is present in standard A provides a positive control, whilst being absent in standard B, thereby providing a negative control. This design enables cross-validation of positive and negative controls between the paired standards in the same reaction, with identical conditions. This enables control and test failures to be distinguished, increasing confidence in the accuracy of results. The chimeric A/B standards were assessed using the US Centres for Disease Control real-time RT-PCR protocol, and showed results congruent with other commercial controls in detecting SARS-CoV-2 in patient samples. This chimeric reference standard design approach offers extensive flexibility, allowing representation of diverse genetic features and distantly related sequences, even from different organisms.


Assuntos
Quimera , Sequência de Aminoácidos , /virologia , Humanos , RNA Viral/normas , Padrões de Referência , Reprodutibilidade dos Testes , /genética , Sensibilidade e Especificidade
4.
Gene ; 767: 145186, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32998045

RESUMO

In ciliates, with every sexual event the transcriptionally active genes of the sub-chromosomic somatic genome that resides in the cell macronucleus are lost. They are de novo assembled starting from 'Macronuclear Destined Sequences' that arise from the fragmentation of transcriptionally silent DNA sequences of the germline chromosomic genome enclosed in the cell micronucleus. The RNA-mediated epigenetic mechanism that drives the assembly of these sequences is subject to errors which result in the formation of chimeric genes. Studying a gene family that in Euplotes raikovi controls the synthesis of protein signal pheromones responsible for a self/not-self recognition mechanism, we identified the chimeric structure of an 851-bp macronuclear gene previously known to specify soluble and membrane-bound pheromone molecules through an intron-splicing mechanism. This chimeric gene, designated mac-er-1*, conserved the native pheromone-gene structure throughout its coding and 3' regions. Instead, its 5' region is completely unrelated to the pheromone gene structure at the level of a 360-bp sequence, which derives from the assembly with a MDS destined to compound a 2417-bp gene encoding a 696-amino acid protein with unknown function. This mac-er-1* gene characterization provides further evidence that ciliates rely on functional chimeric genes that originate in non-programmed phenomena of somatic MDS recombination to increase the species genetic variability independently of gene reshuffling phenomena of the germline genome.


Assuntos
Quimera/genética , Euplotes/genética , Feromônios/genética , Sequência de Aminoácidos/genética , Sequência de Bases/genética , Cilióforos/genética , DNA/genética , Rearranjo Gênico/genética , Íntrons/genética , RNA/genética , Processamento de RNA/genética
5.
Xenobiotica ; 51(1): 51-60, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32779988

RESUMO

The unbound fractions in plasma (f up) in two mouse models of humanized liver mice, PXB and humanized TK-NOG mice, were compared with human f up values using equilibrium dialysis method. A good relationship between f up values obtained from PXB mice and humans was observed; the f up of 34/39 compounds (87.2%) in PXB mice were within 3-fold of human f up. In contrast, a weak correlation was observed between human and humanized TK-NOG mouse f up values; the f up of 15/24 compounds (62.5%) in humanized TK-NOG mice were within 3-fold of human f up. As different profiles of plasma protein binding (PPB) profiles were observed between PXB and humanized TK-NOG mice, f up evaluation is necessary in each mouse model to utilize these humanized liver mice for pharmacological, drug-drug interaction (DDI), and toxicity studies. The unbound fraction in the mixed plasma of human and SCID mouse plasma (85:15) was well correlated with f up in PXB mice (38/39 compounds within a 3-fold). Thus, this artificial PXB mouse plasma could be used to evaluate PPB.


Assuntos
Preparações Farmacêuticas/metabolismo , Animais , Quimera , Modelos Animais de Doenças , Hepatócitos/metabolismo , Humanos , Fígado/metabolismo , Camundongos , Camundongos SCID , Ligação Proteica/fisiologia
7.
J Surg Res ; 257: 462-467, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32896814

RESUMO

BACKGROUND: In utero hematopoietic cell transplantation (IUHCT) has been demonstrated to reliably generate chimeric offspring. This technique introduces transplanted cells into a fetus while the immune system is still developing, allowing for engraftment without the need for myeloablation. However, little is known about the effect of engraftment on the gonadal tissue or within the germ line of the resultant chimeras. MATERIALS AND METHODS: BALB/cJ mice pups were injected with B6-green fluorescent protein mononuclear bone marrow (BM) cells at gestational ages E13 or E14. Two female and two male chimeras were then crossbred with untreated mice. The gonadal tissue of the chimeras was evaluated with fluorescent stereomicroscopy and green fluorescent protein histologic staining. The progeny of the cross-bred mice was analyzed using flow cytometric evaluation of both the peripheral blood and BM. RESULTS: Although transplanted cells engrafted within the gonads, no evidence of chimerism was found in oocytes or spermatogonia of female and male mice treated with IUHCT, respectively. Crossbreeding chimeric mice with untreated mice generated progeny without evidence of chimerism in peripheral blood and BM. CONCLUSIONS: IUHCT yields chimeric mice that have engrafted cells within the gonads but not within the germ line itself. Correspondingly, progeny from the unaltered germ line has no detectable chimerism. This has clinical implications as the offspring of future patients treated with IUHCT would carry the disease for which their parents were treated with IUHCT.


Assuntos
Quimera , Terapias Fetais , Células Germinativas , Transplante de Células-Tronco Hematopoéticas , Animais , Feminino , Masculino , Camundongos Endogâmicos BALB C
8.
PLoS One ; 15(12): e0243580, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33332448

RESUMO

Continued drought during the late growth stage of super hybrid rice (SHR) markedly reduces yield, and management practices that use water more efficiently can contribute greatly to high and stable yields from SHR. The absolute temperature differences (ATDs) between the rice plant and the atmosphere and between the soil and the atmosphere are believed to be important determinants of grain yield. However, it has not previously been determined whether these ATDs have any effect on SHR yields under water-saving cultivation. A two-year field experiment involving two SHR varieties, Liangyoupeijiu (LYPJ) and Y-Liangyou 9000 (YLY900), evaluated the effects of reducing water supply from mid-booting to maturity on grain yield, canopy relative humidity (CRH), leaf area index (LAI), and ATDs between the ambient temperature and the leaf surface, panicles, canopy, and soil. Grain yield increased significantly under shallow water irrigation (SW), by 8.84% (YLY900) and 12.26% (LYPJ), but decreased significantly under mild water stress (MS, -20 to -30 kPa), by 14.36% (YLY900) and 9.47% (LYPJ), as well as severe water stress (SS, -40 to -50 kPa), by 35.06% (YLY900) and 28.74% (LYPJ). As water supply decreased, so did the CRH and the ATDs, with significant decreases under MS and SS. The temperature differences were significantly and positively correlated with grain yield (P < 0.01) in both cultivars. LAI was increased under SW conditions, but was significantly decreased under MS and SS. Our study suggests that the dual goal of saving water while maintaining high yield can be achieved by applying SW irrigation from mid-booting to maturity and by adopting cultivation measures that maintain high CRH and high plant-atmosphere and soil-atmosphere ATDs in order to alleviate water stress. YLY900 has a higher yield potential than LYPJ under SW conditions, suggesting that its wide cultivation may help achieve this dual goal.


Assuntos
Irrigação Agrícola , Oryza/crescimento & desenvolvimento , Irrigação Agrícola/métodos , Atmosfera , Quimera/crescimento & desenvolvimento , Grão Comestível/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Solo/química , Temperatura
9.
PLoS One ; 15(10): e0232071, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33052925

RESUMO

A PVL-positive, methicillin-susceptible Staphylococcus aureus was cultured from pus from cervical lymphadenitis of a patient of East-African origin. Microarray hybridisation assigned the isolate to clonal complex (CC) 80 but revealed unusual features, including the presence of the ORF-CM14 enterotoxin homologue and of an ACME-III element as well as the absence of etD and edinB. The isolate was subjected to both, Illumina and Nanopore sequencing allowing characterisation of deviating regions within the strain´s genome. Atypical features of this strain were attributable to the presence of two genomic regions that originated from other S. aureus lineages and that comprised, respectively, 3% and 1.4% of the genome. One deviating region extended from walJ to sirB. It comprised ORF-CM14 and the ACME-III element. A homologous but larger fragment was also found in an atypical S. aureus CC1/ST567 strain whose lineage might have served as donor of this genomic region. This region itself is a chimera comprising fragments from CC1 as well as fragments of unknown origin. The other deviating region comprised the region from htsB to ecfA2, i.e., another 3% of the genome. It was very similar to CC1 sequences. Either this suggests an incorporation of CC1 DNA into the study strain, or alternatively a recombination event affecting "canonical" CC80. Thus, the study strain bears witness of several recombination events affecting supposedly core genomic genes. Although the exact mechanism is not yet clear, such chimerism seems to be an additional pathway in the evolution of S. aureus. This could facilitate also a transmission of virulence and resistance factors and therefore offer an additional evolutionary advantage.


Assuntos
Proteínas de Bactérias/genética , Linfadenite/microbiologia , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Infecções Estafilocócicas/diagnóstico , Staphylococcus aureus/crescimento & desenvolvimento , Quimera/genética , Quimera/crescimento & desenvolvimento , Evolução Molecular , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Pessoa de Meia-Idade , Mutagênese Insercional , Recombinação Genética , Análise de Sequência de DNA , Staphylococcus aureus/genética , Staphylococcus aureus/isolamento & purificação , Supuração
10.
Trends Pharmacol Sci ; 41(10): 684-686, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32893006

RESUMO

In a recent study, Saraswat and colleagues identified a novel proteolysis targeting chimera (PROTAC), ARV-825 (ARV), that efficiently degrades bromodomain-containing protein 4 (BRD4) to drug the 'undruggable' MYC in pancreatic cancer. ARV-loaded polyethylene glycol-poly lactic acid-co-glycolic acid (PLGA-PEG) polymeric nanoparticles (ARV-NPs) showed promising anticancer activity in both 2D cell culture and 3D multicellular tumor spheroid models of pancreatic cancer. This study demonstrates a unique therapeutic strategy in which targeting BRD4 for degradation via the E3 ubiquitin ligase cereblon (CRBN) pathway leads to sustained inhibition of oncogenic MYC expression for effective treatment of pancreatic cancer.


Assuntos
Proteínas Nucleares , Neoplasias Pancreáticas , Proteínas Adaptadoras de Transdução de Sinal , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Quimera/metabolismo , Humanos , Proteínas Nucleares/metabolismo , Neoplasias Pancreáticas/tratamento farmacológico , Peptídeo Hidrolases , Proteólise , Fatores de Transcrição/metabolismo , Ubiquitina-Proteína Ligases
11.
Nat Protoc ; 15(10): 3154-3181, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778838

RESUMO

We provide a protocol for generating forebrain structures in vivo from mouse embryonic stem cells (ESCs) via neural blastocyst complementation (NBC). We developed this protocol for studies of development and function of specific forebrain regions, including the cerebral cortex and hippocampus. We describe a complete workflow, from methods for modifying a given genomic locus in ESCs via CRISPR-Cas9-mediated editing to the generation of mouse chimeras with ESC-reconstituted forebrain regions that can be directly analyzed. The procedure begins with genetic editing of mouse ESCs via CRISPR-Cas9, which can be accomplished in ~4-8 weeks. We provide protocols to achieve fluorescent labeling of ESCs in ~2-3 weeks, which allows tracing of the injected, ESC-derived donor cells in chimeras generated via NBC. Once modified ESCs are ready, NBC chimeras are generated in ~3 weeks via injection of ESCs into genetically programmed blastocysts that are subsequently transferred into pseudo-pregnant fosters. Our in vivo brain organogenesis platform is efficient, allowing functional and systematic analysis of genes and other genomic factors in as little as 3 months, in the context of a whole organism.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/embriologia , Células-Tronco Embrionárias Murinas/fisiologia , Animais , Blastocisto , Diferenciação Celular , Quimera , Feminino , Masculino , Camundongos , Organogênese , Fenótipo
12.
Science ; 369(6504): 618-619, 2020 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-32764051
14.
J Exp Med ; 217(11)2020 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-32692348

RESUMO

The emergence of SARS-CoV-2 and the ensuing explosive epidemic of COVID-19 disease has generated a need for assays to rapidly and conveniently measure the antiviral activity of SARS-CoV-2-specific antibodies. Here, we describe a collection of approaches based on SARS-CoV-2 spike-pseudotyped, single-cycle, replication-defective human immunodeficiency virus type-1 (HIV-1), and vesicular stomatitis virus (VSV), as well as a replication-competent VSV/SARS-CoV-2 chimeric virus. While each surrogate virus exhibited subtle differences in the sensitivity with which neutralizing activity was detected, the neutralizing activity of both convalescent plasma and human monoclonal antibodies measured using each virus correlated quantitatively with neutralizing activity measured using an authentic SARS-CoV-2 neutralization assay. The assays described herein are adaptable to high throughput and are useful tools in the evaluation of serologic immunity conferred by vaccination or prior SARS-CoV-2 infection, as well as the potency of convalescent plasma or human monoclonal antibodies.


Assuntos
Anticorpos Neutralizantes/análise , Anticorpos Antivirais/análise , Betacoronavirus/imunologia , Infecções por Coronavirus/imunologia , Imunoensaio/métodos , Pneumonia Viral/imunologia , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Betacoronavirus/genética , Linhagem Celular , Quimera/genética , Quimera/imunologia , Chlorocebus aethiops , Infecções por Coronavirus/virologia , Células HEK293 , HIV-1/genética , HIV-1/imunologia , Humanos , Testes de Neutralização/métodos , Pandemias , Pneumonia Viral/virologia , Recombinação Genética , Glicoproteína da Espícula de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/imunologia , Células Vero , Vírus da Estomatite Vesicular Indiana/genética , Vírus da Estomatite Vesicular Indiana/imunologia
16.
Nat Commun ; 11(1): 3154, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32572025

RESUMO

An orthogonal aminoacyl-tRNA synthetase/tRNA pair is a crucial prerequisite for site-specific incorporation of unnatural amino acids. Due to its high codon suppression efficiency and full orthogonality, the pyrrolysyl-tRNA synthetase/pyrrolysyl-tRNA pair is currently the ideal system for genetic code expansion in both eukaryotes and prokaryotes. There is a pressing need to discover or engineer other fully orthogonal translation systems. Here, through rational chimera design by transplanting the key orthogonal components from the pyrrolysine system, we create multiple chimeric tRNA synthetase/chimeric tRNA pairs, including chimera histidine, phenylalanine, and alanine systems. We further show that these engineered chimeric systems are orthogonal and highly efficient with comparable flexibility to the pyrrolysine system. Besides, the chimera phenylalanine system can incorporate a group of phenylalanine, tyrosine, and tryptophan analogues efficiently in both E. coli and mammalian cells. These aromatic amino acids analogous exhibit unique properties and characteristics, including fluorescence, post-translation modification.


Assuntos
Aminoácidos/biossíntese , Código Genético , RNA de Transferência , Biologia Sintética/métodos , Alanina/análogos & derivados , Quimera/genética , Quimera/metabolismo , Escherichia coli , Células HEK293 , Histidina/análogos & derivados , Humanos , Lisina/análogos & derivados , Fenilalanina/análogos & derivados , RNA de Transferência/genética , RNA de Transferência/metabolismo , Triptofano/análogos & derivados , Tirosina/análogos & derivados
17.
J Virol ; 94(17)2020 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-32581110

RESUMO

The classical swine fever virus (CSFV) live attenuated vaccine C-strain is adaptive to rabbits and attenuated in pigs, in contrast with the highly virulent CSFV Shimen strain. Previously, we demonstrated that P108 and T109 on the E2 glycoprotein (E2P108-T109) in domain I (E2DomainI) rather than R132, S133, and D191 in domain II (E2DomainII) determine C-strain's adaptation to rabbits (ATR) (Y. Li, L. Xie, L. Zhang, X. Wang, C. Li, et al., Virology 519:197-206, 2018). However, it remains elusive whether these critical amino acids affect the ATR of the Shimen strain and virulence in pigs. In this study, three chimeric viruses harboring E2P108-T109, E2DomainI, or E2DomainII of C-strain based on the non-rabbit-adaptive Shimen mutant vSM-HCLVErns carrying the Erns glycoprotein of C-strain were generated and evaluated. We found that E2P108-T109 or E2DomainI but not E2DomainII of C-strain renders vSM-HCLVErns adaptive to rabbits, suggesting that E2P108-T109 in combination with the Erns glycoprotein (E2P108-T109-Erns) confers ATR on the Shimen strain, creating new rabbit-adaptive CSFVs. Mechanistically, E2P108-T109-Erns of C-strain mediates viral entry during infection in rabbit spleen lymphocytes, which are target cells of C-strain. Notably, pig experiments showed that E2P108-T109-Erns of C-strain does not affect virulence compared with the Shimen strain. Conversely, the substitution of E2DomainII and Erns of C-strain attenuates the Shimen strain in pigs, indicating that the molecular basis of the CSFV ATR and that of virulence in pigs do not overlap. Our findings provide new insights into the mechanism of adaptation of CSFV to rabbits and the molecular basis of CSFV adaptation and attenuation.IMPORTANCE Historically, live attenuated vaccines produced by blind passage usually undergo adaptation in cell cultures or nonsusceptible hosts and attenuation in natural hosts, with a classical example being the classical swine fever virus (CSFV) lapinized vaccine C-strain, which was developed by hundreds of passages in rabbits. However, the mechanism of viral adaptation to nonsusceptible hosts and the molecular basis for viral adaptation and attenuation remain largely unknown. In this study, we demonstrated that P108 and T109 on the E2 glycoprotein together with the Erns glycoprotein of the rabbit-adaptive C-strain confer adaptation to rabbits on the highly virulent CSFV Shimen strain by affecting viral entry during infection but do not attenuate the Shimen strain in pigs. Our results provide vital information on the different molecular bases of CSFV adaptation to rabbits and attenuation in pigs.


Assuntos
Adaptação Fisiológica/fisiologia , Vírus da Febre Suína Clássica/fisiologia , Peste Suína Clássica/imunologia , Glicoproteínas/química , Proteínas do Envelope Viral/química , Animais , Linhagem Celular , Quimera , Peste Suína Clássica/prevenção & controle , Peste Suína Clássica/virologia , Modelos Animais de Doenças , Genoma Viral , Glicoproteínas/genética , Coelhos , Receptor EphB2 , Baço/virologia , Suínos , Vacinas Atenuadas , Proteínas do Envelope Viral/genética , Vacinas Virais/imunologia , Viremia , Virulência , Internalização do Vírus , Replicação Viral
18.
Science ; 368(6492): 731-736, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32409469

RESUMO

The establishment of reproductive barriers between populations can fuel the evolution of new species. A genetic framework for this process posits that "incompatible" interactions between genes can evolve that result in reduced survival or reproduction in hybrids. However, progress has been slow in identifying individual genes that underlie hybrid incompatibilities. We used a combination of approaches to map the genes that drive the development of an incompatibility that causes melanoma in swordtail fish hybrids. One of the genes involved in this incompatibility also causes melanoma in hybrids between distantly related species. Moreover, this melanoma reduces survival in the wild, likely because of progressive degradation of the fin. This work identifies genes underlying a vertebrate hybrid incompatibility and provides a glimpse into the action of these genes in natural hybrid populations.


Assuntos
Ciprinodontiformes/genética , Doenças dos Peixes/genética , Proteínas de Peixes/genética , Hibridização Genética , Melanoma/genética , Melanoma/virologia , Receptores Proteína Tirosina Quinases/genética , Alelos , Nadadeiras de Animais/patologia , Animais , Quimera , Loci Gênicos , Estudo de Associação Genômica Ampla
20.
Am Nat ; 195(6): E150-E167, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32469663

RESUMO

Partial prezygotic isolation is often viewed as more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. I simulate secondary contact between two populations (species) to examine effects of assortative mating and low hybrid fitness in preventing blending. A small reduction in hybrid fitness (e.g., by 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10 times stronger preference for conspecific over heterospecific mates). In the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the buildup of a continuum of intermediates. The weakness of assortative mating compared with reduced fitness of hybrids in preventing blending is robust to varying genetic bases of these traits. Assortative mating is most powerful in limiting blending when it is encoded by a single locus or is essentially complete, or when there is a large mate search cost. In these cases assortative mating is likely to cause hybrids to have low fitness, due to frequency-dependent mating disadvantage of individuals of rare mating types. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.


Assuntos
Quimera/genética , Especiação Genética , Preferência de Acasalamento Animal , Animais , Simulação por Computador , Feminino , Fluxo Gênico , Aptidão Genética , Masculino , Isolamento Reprodutivo
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