Male^male competition and female mate choice act contemporaneously in the cockroach Nauphoeta cinerea and the social pheromone of males in£uences the outcome of both forms of sexual selection. We therefore examined the joint and separate e¡ects of male^male competition and female mate choice to determine if the selective optima for the pheromone were the same or di¡erent. Dominant males in a newly established hierarchy mated more frequently, but not exclusively. Manipulations of the multi-component social pheromone produced by males of N. cinerea showed that both long-and closerange attraction of females by males were in£uenced by the quantity and composition of the pheromone. The most attractive composition, however, di¡ered from that which was most likely to confer high status to males. Since the outcome of male^male competition can con£ict with mating preferences exhibited by females, there is balancing sexual selection on the social pheromone of N. cinerea. Such balancing selection might act to maintain genetic variation in sexually selected traits. We suggest that the di¡erent forms of sexual selection con£ict in N. cinerea because females prefer a blend di¡erent to that which is most e¡ective in male^male competition in order to avoid mating with overly aggressive males.
BackgroundThe function of cytosine (DNA) methylation in insects remains inconclusive due to a lack of mutant and/or genetic studies.ResultsHere, we provide evidence for the functional role of the maintenance DNA methyltransferase 1 (Dnmt1) in an insect using experimental manipulation. Through RNA interference (RNAi), we successfully posttranscriptionally knocked down Dnmt1 in ovarian tissue of the hemipteran Oncopeltus fasciatus (the large milkweed bug). Individuals depleted for Dnmt1, and subsequently DNA methylation, failed to reproduce. Eggs were inviable and declined in number, and nuclei structure of follicular epithelium was aberrant. Erasure of DNA methylation from gene or transposon element bodies did not reveal a direct causal link to steady-state mRNA levels in somatic cells. These results reveal an important function of Dnmt1 seemingly not contingent on directly controlling gene expression.ConclusionsThis study provides direct experimental evidence for a functional role of Dnmt1 in egg production and embryo viability and uncovers a trivial role, if any, for DNA methylation in control of gene expression in O. fasciatus.Electronic supplementary materialThe online version of this article (10.1186/s13072-018-0246-5) contains supplementary material, which is available to authorized users.
Females are expected to have different mating preferences because of the variation in costs and benefits of mate choice both between females and within individual females over a lifetime. Workers have begun to look for, and find, the expected variation among females in expressed mating preferences. However, variation within females caused by changes in intrinsic influences has not been examined in detail. Here we show that reproductive aging caused by delayed mating resulted in reduced choosiness by female Nauphoeta cinerea, a cockroach that has reproductive cycles and gives live birth. Male willingness to mate was unaffected by variation in female age. Females who were beyond the optimal mating age, 6 days postadult molt, required considerably less courtship than their younger counterparts. Females who were older when they mated had fewer offspring per clutch and fewer clutches than females who mated young. Thus, reduced choosiness was correlated with a permanent reduction in fertility. There was no difference in overall senescence among females, and thus the reduction in clutch size did not result in the expected increased lifespan. We suggest that reproductive aging in N. cinerea, similar to aging in general, occurs because the maintenance of oocytes is costly, and selection is relaxed after the optimal mating period. Our results further suggest that selection for continued choosiness is also relaxed and supports direct selection on female choosiness and a cost to choosiness.aging ͉ female mate choice ͉ fitness ͉ mate quality ͉ sexual selection S exual selection theory predicts that mate choice, usually by females, evolves because of variation in benefits provided by mating with particular mates. Much of the recent research on sexual selection therefore has been directed at detecting the benefit provided by males to females (reviewed in refs. 1 and 2). Considerably less research effort has addressed variation in female preferences (3-7). During female mate choice, however, females must tradeoff the benefits gained by being choosy against the costs of stronger preferences (2). This cost͞benefit tradeoff should result in variation in the expression of female mate preferences both between females and by an individual female over her lifetime.Variation in female mate preferences can result from extrinsic or intrinsic factors. Examples of external conditions that may cause females to be less choosy when making mating decisions include environmental conditions that increase the energy output required to search for and compare different males (8) or high predation risk (9-11). Seasonal constraints on reproduction can also influence female choosiness (12).Intrinsic factors should also inf luence the expression of female mate choice (13, 14). Parker's ESS model of mate choice (13) suggests that the level of choosiness is a function of female reproductive quality. Females with a reproductive quality above a certain threshold should only accept mates of similarly high quality. However, females with a reproductive qualit...
Background The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus , a seed feeder of the family Lygaeidae. Results The 926-Mb Oncopeltus genome is well represented by the current assembly and official gene set. We use our genomic and RNA-seq data not only to characterize the protein-coding gene repertoire and perform isoform-specific RNAi, but also to elucidate patterns of molecular evolution and physiology. We find ongoing, lineage-specific expansion and diversification of repressive C2H2 zinc finger proteins. The discovery of intron gain and turnover specific to the Hemiptera also prompted the evaluation of lineage and genome size as predictors of gene structure evolution. Furthermore, we identify enzymatic gains and losses that correlate with feeding biology, particularly for reductions associated with derived, fluid nutrition feeding. Conclusions With the milkweed bug, we now have a critical mass of sequenced species for a hemimetabolous insect order and close outgroup to the Holometabola, substantially improving the diversity of insect genomics. We thereby define commonalities among the Hemiptera and delve into how hemipteran genomes reflect distinct feeding ecologies. Given Oncopeltus ’s strength as an experimental model, these new sequence resources bolster the foundation for molecular research and highlight technical considerations for the analysis of medium-sized invertebrate genomes. Electronic supplementary material The online version of this article (10.1186/s13059-019-1660-0) contains supplementary material, which is available to authorized users.
Abstract. The Golgi apparatus of plant cells is the site of assembly of glycoproteins, proteoglycans, and complex polysaccharides, but little is known about how the different assembly pathways are organized within the Golgi stacks. To study these questions we have employed immunocytochemical techniques and antibodies raised against the hydroxyproline-rich cell wall glycoprotein, extensin, and two types of complex polysaccharides, an acidic pectic polysaccharide known as rhamnogalacturonan I (RG-I), and the neutral hemicellulose, xyloglucan (XG). Our micrographs demonstrate that individual Golgi stacks can process simultaneously glycoproteins and complex polysacchatides. O-linked arabinosylation of the hydroxyproline residues of extensin occurs in cis-cisternae, and glycosylated molecules pass through all cisternae before they are packaged into secretory vesicles in the monensin-sensitive, trans-Golgi network. In contrast, in root tip cortical parenchyma cells, the anti-RG-I and the anti-XG antibodies are shown to bind to complementary subsets of Golgi cisternae, and several lines of indirect evidence suggest that these complex polysaccharides may also exit from different cisternae. Thus, RG-I type polysaccharides appear to be synthesized in cis-and medial cisternae, and have the potential to leave from a monensin-insensitive, medial cisternal compartment. The labeling pattern for XG suggests that it is assembled in trans-Golgi cisternae and departs from the monensin-sensitive trans-Golgi network. This physical separation of the synthesis/secretion pathways of major categories of complex polysaccharides may prevent the synthesis of mixed polysaccharides, and provides a means for producing secretory vesicles that can be targeted to different cell wall domains.
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