RESUMEN
BACKGROUND: Despite the growing interest in the female side of copulatory interactions, the roles played by differential expression and alternative splicing mechanisms of pre-RNA on tissues outside of the reproductive tract have remained largely unknown. Here we addressed these questions in the context of con- vs heterospecific matings between Drosophila mojavensis and its sister species, D. arizonae. We analyzed transcriptional responses in female heads using an integrated investigation of genome-wide patterns of gene expression, including differential expression (DE), alternative splicing (AS) and intron retention (IR). RESULTS: Our results indicated that early transcriptional responses were largely congruent between con- and heterospecific matings but are substantially perturbed over time. Conspecific matings induced functional pathways related to amino acid balance previously associated with the brain's physiology and female postmating behavior. Heterospecific matings often failed to activate regulation of some of these genes and induced expression of additional genes when compared with those of conspecifically-mated females. These mechanisms showed functional specializations with DE genes mostly linked to pathways of proteolysis and nutrient homeostasis, while AS genes were more related to photoreception and muscle assembly pathways. IR seems to play a more general role in DE regulation during the female postmating response. CONCLUSIONS: We provide evidence showing that AS genes substantially perturbed by heterospecific matings in female heads evolve at slower evolutionary rates than the genome background. However, DE genes evolve at evolutionary rates similar, or even higher, than those of male reproductive genes, which highlights their potential role in sexual selection and the evolution of reproductive barriers.
Asunto(s)
Copulación , Transcriptoma , Empalme Alternativo , Animales , Drosophila/genética , Femenino , Masculino , Reproducción , Conducta Sexual AnimalRESUMEN
Even in well-characterized genomes, many transcripts are considered noncoding RNAs (ncRNAs) simply due to the absence of large open reading frames (ORFs). However, it is now becoming clear that many small ORFs (smORFs) produce peptides with important biological functions. In the process of characterizing the ribosome-bound transcriptome of an important cell type of the seminal fluid-producing accessory gland of Drosophila melanogaster, we detected an RNA, previously thought to be noncoding, called male-specific abdominal (msa). Notably, msa is nested in the HOX gene cluster of the Bithorax complex and is known to contain a micro-RNA within one of its introns. We find that this RNA encodes a "micropeptide" (9 or 20 amino acids, MSAmiP) that is expressed exclusively in the secondary cells of the male accessory gland, where it seems to accumulate in nuclei. Importantly, loss of function of this micropeptide causes defects in sperm competition. In addition to bringing insights into the biology of a rare cell type, this work underlines the importance of small peptides, a class of molecules that is now emerging as important actors in complex biological processes.
Asunto(s)
Infertilidad Masculina/genética , Mutación con Pérdida de Función , Espermatozoides/metabolismo , Animales , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Masculino , Péptidos/genética , Péptidos/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
In many animal species, females undergo physiological and behavioral changes after mating. Some of these changes are driven by male-derived seminal fluid proteins and are critical for fertilization success. Unfortunately, our understanding of the molecular interplay between female and male reproductive proteins remains inadequate. Here, we analyze the postmating response in a Drosophila species that has evolved strong gametic incompatibility with its sister species; Drosophila novamexicana females produce only â¼1% fertilized eggs in crosses with Drosophila americana males, compared to â¼98% produced in within-species crosses. This incompatibility is likely caused by mismatched male and female reproductive molecules. In this study, we use short-read RNA sequencing to examine the evolutionary dynamics of female reproductive genes and the postmating transcriptome response in crosses within and between species. First, we found that most female reproductive tract genes are slow-evolving compared to the genome average. Second, postmating responses in con- and heterospecific matings are largely congruent, but heterospecific matings induce expression of additional stress-response genes. Some of those are immunity genes that are activated by the Imd pathway. We also identify several genes in the JAK/STAT signaling pathway that are induced in heterospecific, but not conspecific mating. While this immune response was most pronounced in the female reproductive tract, we also detect it in the female head and ovaries. These results show that the female's postmating transcriptome-level response is determined in part by the genotype of the male, and that divergence in male reproductive genes and/or traits can have immunogenic effects on females.
Asunto(s)
Drosophila/genética , Evolución Molecular , Aislamiento Reproductivo , Animales , Copulación , Drosophila/metabolismo , Femenino , Genitales Femeninos/metabolismo , Masculino , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Proteínas de Plasma Seminal , Transcripción Genética , TranscriptomaRESUMEN
The male seminal fluid contains factors that affect female post-mating behavior and physiology. In Drosophila, most of these factors are secreted by the two epithelial cell types that make up the male accessory gland: the main and secondary cells. Although secondary cells represent only ~4% of the cells of the accessory gland, their contribution to the male seminal fluid is essential for sustaining the female post-mating response. To better understand the function of the secondary cells, we investigated their molecular organization, particularly with respect to the intracellular membrane transport machinery. We determined that large vacuole-like structures found in the secondary cells are trafficking hubs labeled by Rab6, 7, 11 and 19. Furthermore, these organelles require Rab6 for their formation and many are essential in the process of creating the long-term postmating behavior of females. In order to better serve the intracellular membrane and protein trafficking communities, we have created a searchable, online, open-access imaging resource to display our complete findings regarding Rab localization in the accessory gland.
Asunto(s)
Proteínas de Drosophila/metabolismo , Células Endocrinas/citología , Fertilidad , Proteínas de Unión al GTP rab/metabolismo , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Células Endocrinas/metabolismo , Genitales Masculinos/citología , Genitales Masculinos/metabolismo , Masculino , Transporte de Proteínas , Vacuolas/metabolismo , Vacuolas/ultraestructura , Proteínas de Unión al GTP rab/genéticaRESUMEN
The Drosophila melanogaster sex-peptide (melSP) is a seminal fluid component that induces postmating responses (PMR) of females via the sex-peptide receptor (SPR) . Although SP orthologs are found in many Drosophila species, their functions remain poorly characterized. It is unknown whether SP functions are conserved across species or rather specific to each species. Here, we developed a GFP-tagged melSP (G-SP) and used it to visualize cross-species binding activity to the female reproductive system of various species. First we demonstrated that ectopically expressed G-SP induced PMR in D. melanogaster females and bound to the female reproductive system, most notably to the common oviduct. No binding occurred in the females lacking SPR, indicating that G-SP binding was dependent on SPR. Next we tested whether G-SP binds to the common oviducts from 11 Drosophila species using dissected reproductive tracts. The binding was observed in six species belonging to the D. melanogaster species group, but not to those outside the group. Injection of melSP reduced the receptivity of females belonging to the D. melanogaster species group, but not of those outside the group, being consistent with the ability to bind G-SP. Thus the SP-mediated PMR appears to be limited to this species group. SPR was expressed in the oviducts at high levels in this group; therefore, we speculate that an enhanced expression of SPR in the oviduct was critical to establish the SP-mediated PMR during evolution.