ABSTRACT: Honey bee queens undergo dramatic behavioral (e.g., reduced sexual receptivity), physiological (e.g., ovary activation, ovulation, and modulation of pheromone production) and molecular changes after they complete mating. To elucidate how queen post-mating changes are influenced by seminal fluid, a non-spermatozoa-containing component of semen, we injected queens with semen or seminal fluid alone. We assessed queen sexual receptivity, ovary development, worker retinue response (which is influenced by queen pheromone production), and transcriptional changes in queen abdominal fat body and brain tissues. Injection with either seminal fluid or semen resulted in decreased sexual receptivity, increased attractiveness of queens to workers, and altered expression of several genes that are also regulated in naturally mated queens. The post-mating and transcriptional changes of queens receiving seminal fluid were not significantly different from queens treated with seminal fluid, suggesting that components in seminal fluid, such as seminal fluid proteins, are largely responsible for stimulating post-mating changes in queens.
Project description:Queens of social insects make all mate-choice decisions on a single day, except in honeybees whose queens can conduct mating flights for several days even when already inseminated by a number of drones. Honeybees therefore appear to have a unique, evolutionarily derived form of sexual conflict: a queen’s decision to pursue risky additional mating flights is driven by later-life fitness gains from genetically more diverse worker-offspring but reduces paternity shares of the drones she already mated with. We used artificial insemination, RNA-sequencing and electroretinography to show that seminal fluid induces a decline in queen vision by perturbing the phototransduction pathway within 24-48 hours. Follow up field trials revealed that queens receiving seminal fluid flew two days earlier than sister queens inseminated with saline, and failed more often to return. These findings are consistent with seminal fluid components manipulating queen eyesight to reduce queen promiscuity across mating flights.
Project description:Mating causes dramatic changes in female insects at the behavioral, physiological, and molecular levels. The factors driving these changes (e.g., seminal proteins, seminal volume) and the molecular pathways by which these factors are operating have been characterized only in a handful of insect species. Here we use instrumental insemination of honey bee queens to examine the role of the insemination substance (saline vs. semen) and volume (1 vs. 8 uL) in triggering post-mating changes. We also examine differences in gene expression patterns in the fat bodies of queens that have high ovary activation to determine if events during copulation can cause long-term changes in gene expression. We found that the instrumental insemination procedure alone caused cessation of mating flights and triggered ovary activation, with insemination volume contributing to increased ovary activation. Hierarchical clustering grouped queens primarily by insemination substance and then insemination volume, suggesting that while volume may trigger short-term physiological changes, substance plays a greater role in regulating long-term transcriptional changes. There was considerable but not a complete overlap in the gene pathways regulated by these two factors. Comparisons with gene lists from previous studies on queen mating revealed that several of the same biological processes and pathways were regulated, but only one gene (defensin) was found to be regulated in all studies. Our results suggest that both insemination substance and volume trigger molecular post-mating changes by altering overlapping gene pathways involved in honey bee reproduction.
Project description:Mating is fundamental to the success and reproduction of most organisms, although the physiological and transcriptional changes associated with this process have been largely characterized only in Drosophila. In this study, we use honey bees as a model system since their queens undergo massive and permanent physiological and behavioral changes following mating. Previous studies have identified changes associated with the transition from a virgin queen to a fully-mated, egg-laying queen. Here, we further uncouple the mating process to examine the effects of natural mating vs. instrumental insemination and saline vs. semen insemination. We observed significant overlap between our study and analogous studies in Drosophila, suggesting that some post-mating mechanisms are conserved across insect orders.
Project description:In species with social hierarchies, the death of dominant individuals typically upheaves the social hierarchy and provides an opportunity for subordinate individuals to become reproductives. Such a phenomenon occurs in the monogyne form of the fire ant, Solenopsis invicta, where colonies typically contain a single wingless reproductive queen, thousands of workers and hundreds of winged non-reproductive virgin queens. Upon the death of the mother queen, many virgin queens shed their wings and initiate reproductive development instead of departing on a mating flight. Workers progressively execute almost all of them over the following weeks. To identify the molecular changes that occur in virgin queens as they perceive the loss of their mother queen and begin to compete for reproductive dominance, we collected virgin queens before the loss of their mother queen, six hours after orphaning and 24 hours after orphaning. Their RNA was extracted and hybridized against microarrays to examine the expression levels of approximately 10,000 genes. We identified 297 genes that were consistently differentially expressed after orphaning. These include genes that are putatively involved in the signaling and onset of reproductive development, as well as genes underlying major physiological changes in the young queens.
Project description:Polyandrous ant queens are inseminated early in their life and store sperm mixtures for a potential reproductive life of decades. However, they cannot re-mate later in life and are thus expected to control the loss of viable sperm because their life-time reproductive success is ultimately limited by the viability of sperm obtained in their single reproductive event. In the leaf-cutting ant Atta colombica, we have previously shown that sperm survival is lowered when getting in contact with seminal fluid of other males, and remains stable when in contact with secretions of the queen sperm storage organ (spermatheca). Here we aim to resolve the main protein-level interactions that mediate sperm competition dynamics and sperm preservation. We used artificial insemination and DIGE-based proteomics to identify proteomic changes when seminal fluid is exposed to spermathecal fluid. Seminal fluid was collected from mature males during field season experiments in Panama, by gently squeezing males’ abdomen until the ejaculate came out. Ejaculates from several males were kept together in ice and then centrifuged for 10 minutes at 13,500 g, the supernatant collected in a separate tube and then centrifuged again. The resulting supernatant was then transferred to another tube and stored at -20° C until further use. Four biological replicates of SF were collected from 4 colonies, each consisting of 400 µl SF from approximately 350 males. From each biological replicate three 100 µl aliquots were retrieved, and assigned to one of the following treatments: (1) un-inseminated controls, (2) inseminated SF retrieved after 30 min, and (3) inseminated SF retrieved after 12 h (Fig 1). Next, each of those aliquots was used to artificially inseminate 10 virgin queens (10 µl of aliquot per queen), for a total of 80 queens inseminated. Queens were allowed to recover for 30 min or 12 h before dissecting them to obtain the spermathecal content. All these spermathecal contents were then pooled per treatment and replicate, resulting in a total of 12 samples (3 treatments – un-inseminated SF, inseminated SF retrieved after 30 min inside the queen, and inseminated SF retrieved after 12 hours inside the queen - with 4 biological replicates). Proteins were precipitated in each sample by adding 4 volumes of ice-cold acetone for 4 hours at -20°C and centrifuged at 14,000 g for 10 minutes, after which supernatants were discarded and the protein pellets were stored at -80°C until further use. All of those 12 samples entered the DIGE analysis.
Project description:To examine the effect of seminal fluid on the whole genome expression profile of endometrial tissue following mating, RNA was extracted from endometrial tissue collected 8 h after CBAF1 females were mated with intact Balb/c males and compared to RNA from endometrial tissue of females mated with seminal fluid deficient SVX/VAS Balb/c males. This comparison controlled for ovarian hormone status, exposure to the male and mating activity, and the neuroendocrine response to cervical and vaginal stimulus at mating, so that changes in endometrial gene expression could be attributed specifically to contact with seminal fluid. The endometrial RNA from n=16 individual females was pooled into four independent biological replicates per treatment group (n=4 endometrial samples per replicate) and expression profiles were analyzed by Affymetrix microarray. Seminal fluid exposure induced a clear difference in the profile of genes expressed in the endometrium with a total of 335 genes were differentially regulated with a fold-change greater than 1.5 and p<0.05. Of these, 190 genes were upregulated and 145 genes were downregulated following contact with seminal fluid. Bioinformatics analysis revealed TLR4 signaling as a strongly predicted upstream regulator activated by the differentially expressed genes.Additional experiments confirmed the role of TLR4 with the absence of TLR4 in TLR4 null mice resulting in a failure for seminal fluid to induce endometrial Csf3, Cxcl2, Il6 and Tnf expression. This study provides evidence that TLR4 contributes to seminal fluid modulation of the periconception immune environment. Activation of TLR4 signaling by microbial or endogenous components of seminal fluid is thus implicated as a key element of the female tract response to seminal fluid at the outset of pregnancy in mice.
Project description:Mating is a complex process, which is frequently associated with behavioural and physiological changes. However, understanding of the genetic underpinnings of these changes is limited. Honey bees are both a model system in behavioural genomics, and the dominant managed pollinator of human crops; consequently understanding the mating process has both pure and applied value. We used next-generation transcriptomics to probe changes in gene expression in the brains of honey bee queens, as they transition from virgin to mated reproductive status. In addition, we used CO2-narcosis, which induces oviposition without mating, as an experimental control for the mating process. Mating produced significant changes in the expression of vision, chemo-reception, metabolic, and immune-related genes. Differential expression of these genes maps clearly onto known behavioural and physiological changes that occur during the transition from being a virgin queen to a newly-mated queen. A subset of these changes in gene expression were also detected in CO2-treated queens, as predicted from previous physiological studies. In addition, we compared our results to previous studies that used microarray techniques across a range of experimental time-points. Changes in expression of immune- and vision-related genes were common to all studies, supporting an involvement of these groups of genes in the mating process. However, these comparisons also indicate the need to understand the temporal dynamics of gene expression across the entire mating and reproductive process.
Project description:Modes of sexual reproduction in eukaryotic organisms are highly diversified. The human fungal pathogen Candida albicans undergoes a phenotypic switch from the white to the opaque phase in order to become mating-competent. In this study, we report that functionally and morphologically differentiated white and opaque cells show a coordinating behavior in the process of mating. Although white cells are mating-incompetent, they are induced to produce sexual pheromones when treated with opposite pheromones or interacted with opaque cells of an opposite mating type. In a co-culture system, pheromones released by white cells induce opaque cells to form mating projections and thus facilitate both opposite- and same-sex mating of opaque cells. Deletion of genes encoding the pheromone precursor proteins and inactivation of the pheromone response signaling pathway (Ste2-MAPK-Cph1) impair the promoting role of white cells (MTLa) in sexual mating of opaque cells. White and opaque cells communicate via a paracrine pheromone signaling and thus create an environment conducive to sexual mating. This coordination behavior of the two different cell types may be a trade-off strategy between sexual and asexual lifestyles in C. albicans. total RNA profiles of white cell treated with pheromone
Project description:Modes of sexual reproduction in eukaryotic organisms are highly diversified. The human fungal pathogen Candida albicans undergoes a phenotypic switch from the white to the opaque phase in order to become mating-competent. In this study, we report that functionally and morphologically differentiated white and opaque cells show a coordinating behavior in the process of mating. Although white cells are mating-incompetent, they are induced to produce sexual pheromones when treated with opposite pheromones or interacted with opaque cells of an opposite mating type. In a co-culture system, pheromones released by white cells induce opaque cells to form mating projections and thus facilitate both opposite- and same-sex mating of opaque cells. Deletion of genes encoding the pheromone precursor proteins and inactivation of the pheromone response signaling pathway (Ste2-MAPK-Cph1) impair the promoting role of white cells (MTLa) in sexual mating of opaque cells. White and opaque cells communicate via a paracrine pheromone signaling and thus create an environment conducive to sexual mating. This coordination behavior of the two different cell types may be a trade-off strategy between sexual and asexual lifestyles in C. albicans.