The evolution of seminal fluid gene expression and postmating reproductive isolation in Drosophila.

Seminal fluid protein (Sfp) genes show, in general, a higher rate of sequence divergence than genes from other categories, which is often attributed to forms of postcopulatory sexual selection or sexual conflict. Recently, the relaxation of selective constraints has been proposed as an alternative explanation for the rapid sequence evolution of Sfps and other genes with sex-limited expression. The expression of Sfp genes is a likely target of selection, but the evolution of differences in their expression levels is less understood.

A predominant role of genotypic variation in both expression of sperm competition genes and paternity success in .

Sperm competition is a crucial aspect of male reproductive success in many species, including and seminal fluid proteins (Sfps) can influence sperm competitiveness. However, the combined effect of environmental and genotypic variation on sperm competition gene expression remains poorly understood. Here, we used Genetic Reference Panel (DGRP) inbred lines and manipulated developmental population density (i.

Indel driven rapid evolution of core nuclear pore protein gene promoters.

Nuclear pore proteins (Nups) prominently are among the few genes linked to speciation from hybrid incompatibility in Drosophila. These studies have focused on coding sequence evolution of Nup96 and Nup160 and shown evidence of positive selection driving nucleoporin evolution. Intriguingly, channel Nup54 functionality is required for neuronal wiring underlying the female post-mating response induced by male-derived sex-peptide.

Gene expression differentiation in the reproductive tissues of Drosophila willistoni subspecies and their hybrids.

Early lineage diversification is central to understand what mutational events drive species divergence. Particularly, gene misregulation in interspecific hybrids can inform about what genes and pathways underlie hybrid dysfunction. In Drosophila hybrids, how regulatory evolution impacts different reproductive tissues remains understudied.

Drosophila as a Model for Human Viral Neuroinfections.

The study of human neurological infection faces many technical and ethical challenges. While not as common as mammalian models, the use of (fruit fly) in the investigation of virus-host dynamics is a powerful research tool. In this review, we focus on the benefits and caveats of using as a model for neurological infections and neuroimmunity.

Seminal fluid gene expression and reproductive fitness in Drosophila melanogaster.

Background: The rapid evolution of seminal fluid proteins (SFPs) has been suggested to be driven by adaptations to postcopulatory sexual selection (e.g. sperm competition).

Divergence of X-linked trans regulatory proteins and the misexpression of gene targets in sterile Drosophila pseudoobscura hybrids.

Background: The genetic basis of hybrid incompatibilities is characterized by pervasive cases of gene interactions. Sex chromosomes play a major role in speciation and X-linked hybrid male sterility (HMS) genes have been identified. Interestingly, some of these genes code for proteins with DNA binding domains, suggesting a capability to act as trans-regulatory elements and disturb the expression of a large number of gene targets.

Channel nuclear pore protein 54 directs sexual differentiation and neuronal wiring of female reproductive behaviors in Drosophila.

Background: Female reproductive behaviors and physiology change profoundly after mating. The control of pregnancy-associated changes in physiology and behaviors are largely hard-wired into the brain to guarantee reproductive success, yet the gene expression programs that direct neuronal differentiation and circuit wiring at the end of the sex determination pathway in response to mating are largely unknown. In Drosophila, the post-mating response induced by male-derived sex-peptide in females is a well-established model to elucidate how complex innate behaviors are hard-wired into the brain.

Nonadaptive molecular evolution of seminal fluid proteins in Drosophila.

Seminal fluid proteins (SFPs) are a group of reproductive proteins that are among the most evolutionarily divergent known. As SFPs can impact male and female fitness, these proteins have been proposed to evolve under postcopulatory sexual selection (PCSS). However, the fast change of the SFPs can also result from nonadaptive evolution, and the extent to which selective constraints prevent SFPs rapid evolution remains unknown.

Expression of and is Needed for Effective Sperm Storage and Egg Fertilization in .

In , male reproductive fitness can be affected by any number of processes, ranging from development of gametes, transfer to and storage of mature sperm within the female sperm storage organs, and utilization of sperm for fertilization. We have previously identified the 89B cytogenetic map position of as a hub for genes that effect male paternity success when disturbed. Here, we used RNA interference to test 11 genes that are highly expressed in the testes and located within the 89B region for their role in sperm competition and male fecundity when their expression is perturbed.

Hybrid Incompatibilities and Transgressive Gene Expression Between Two Closely Related Subspecies of .

Genome-wide assays of expression between species and their hybrids have identified genes that become either over- or underexpressed relative to the parental species (i.e., transgressive).

Speciation and changes in male gene expression in .

It has long been acknowledged that changes in the regulation of gene expression may account for major organismal differences. However, we still do not fully understand how changes in gene expression evolve and how do such changes influence organisms' differences. We are even less aware of the impact such changes might have in restricting gene flow between species.

Reproductive isolation caused by azoospermia in sterile male hybrids of .

Recently diverged populations in the early stages of speciation offer an opportunity to understand mechanisms of isolation and their relative contributions. is a tropical species with broad distribution from Argentina to the southern United States, including the Caribbean islands. A postzygotic barrier between northern populations (North America, Central America, and the northern Caribbean islands) and southern populations (South American and the southern Caribbean islands) has been recently documented and used to propose the existence of two different subspecies.

Genetic Factors Influencing Sperm Competition.

Females of many different species often mate with multiple males, creating opportunities for competition among their sperm. Although originally unappreciated, sperm competition is now considered a central form of post-copulatory male-male competition that biases fertilization. Assays of differences in sperm competitive ability between males, and interactions between females and males, have made it possible to infer some of the main mechanisms of sperm competition.

Altered expression of cell adhesion genes and hybrid male sterility between subspecies of .

and are two closely related subspecies with incomplete reproductive isolation. A genome-wide comparison of expression in hybrids relative to parental subspecies has been previously used to identify genes with significant changes in expression uniquely associated with the sterile condition. The misexpression (i.

Testes Proteases Expression and Hybrid Male Sterility Between Subspecies of .

Hybrid male sterility (HMS) is a form of postmating postzygotic isolation among closely related species that can act as an effective barrier to gene flow. The Dobzhansky-Muller model provides a framework to explain how gene interactions can cause HMS between species. Genomics highlights the preponderance of non-coding DNA targets that could be involved in gene interactions resulting in gene expression changes and the establishment of isolating barriers.

Postmating Reproductive isolation between strains of Drosophila willistoni.

Speciation can occur through the presence of reproductive isolation barriers that impede mating, restrict cross-fertilization, or render inviable/sterile hybrid progeny. The D. willistoni subgroup is ideally suited for studies of speciation, with examples of both allopatry and sympatry, a range of isolation barriers, and the availability of one species complete genome sequence to facilitate genetic studies of divergence.

Misregulation of Gene Expression and Sterility in Interspecies Hybrids: Causal Links and Alternative Hypotheses.

Understanding the origin of species is of interest to biologist in general and evolutionary biologist in particular. Hybrid male sterility (HMS) has been a focus in studies of speciation because sterility imposes a barrier to free gene flow between organisms, thus effectively isolating them as distinct species. In this review, I focus on the role of differential gene expression in HMS and speciation.

Genome Hotspots for Nucleotide Substitutions and the Evolution of Influenza A (H1N1) Human Strains.

In recent years a number of studies have brought attention to the role of positive selection during the evolution of antigenic escape by influenza strains. Particularly, the identification of positively selected sites within antigenic domains of viral surface proteins has been used to suggest that the evolution of viral-host receptor binding specificity is driven by selection. Here we show that, following the 1918 outbreak, the antigenic sites of the hemagglutinin (HA) viral surface protein and the stalk region of neuraminidase became substitution hotspots.

Hybrid male sterility and genome-wide misexpression of male reproductive proteases.

Hybrid male sterility is a common barrier to gene flow between species. Previous studies have posited a link between misregulation of spermatogenesis genes in interspecies hybrids and sterility. However, in the absence of fully fertile control hybrids, it is impossible to differentiate between misregulation associated with sterility vs.

Hybrid male sterility between Drosophila willistoni species is caused by male failure to transfer sperm during copulation.

Background: The biological concept of species stresses the importance of understanding what mechanisms maintain species reproductively isolated from each other. Often such mechanisms are divided into premating and postmating, with the latest being the result of either prezygotic or postzygotic isolation barriers. Drosophila willistoni quechua and Drosophila willistoni willistoni are two subspecies that experience reproductive isolation.

Adaptive evolution at immune system genes and deep pregnancy implantation in primates.

A major evolutionary change in the lineage ancestral to humans, chimpanzee and gorilla (HCG) has been the embedding of the embryo into maternal tissue. Thus, the first layer of cells (trophoblast) to differentiate after fertilization must adapt to invade the uterus. Such event would likely leave signatures of positive selection at genes with roles in embryo implantation.

Positive selection at a seminal fluid gene within a QTL for conspecific sperm precedence.

The role of sexual selection in driving the rapid evolution of male reproductive proteins has been tested in a wide variety of organisms. Sperm competition is a form of postmating sexual selection that can contribute to reproductive isolation between species by biasing the proportion of progeny fathered by conspecific over heterospecific males. This phenomenon is known as conspecific sperm precedence (CSP).

Do candidate genes mediating conspecific sperm precedence affect sperm competitive ability within species? A test case in Drosophila.

When females mate to multiple males, the last male to mate fathers the majority of progeny. When males of different species inseminate a female, the sperm of the male conspecific to the female is favored in fertilization in a process known as conspecific sperm precedence (CSP). A large number of studies in Drosophila have assayed the genetic basis of sperm competition, with a main focus on D.

Positive selection in the adhesion domain of Mus sperm Adam genes through gene duplications and function-driven gene complex formations.

Background: Sperm and testes-expressed Adam genes have been shown to undergo bouts of positive selection in mammals. Despite the pervasiveness of positive selection signals, it is unclear what has driven such selective bouts. The fact that only sperm surface Adam genes show signals of positive selection within their adhesion domain has led to speculation that selection might be driven by species-specific adaptations to fertilization or sperm competition.