Sexual dimorphisms in trait expression are widespread among animals and are especially pronounced in ornaments and weapons of sexual selection, which can attain exaggerated sizes. Expression of ...exaggerated traits is usually male-specific and nutrition sensitive. Consequently, the developmental mechanisms generating sexually dimorphic growth and nutrition-dependent phenotypic plasticity are each likely to regulate the expression of extreme structures. Yet we know little about how either of these mechanisms work, much less how they might interact with each other. We investigated the developmental mechanisms of sex-specific mandible growth in the stag beetle Cyclommatus metallifer, focusing on doublesex gene function and its interaction with juvenile hormone (JH) signaling. doublesex genes encode transcription factors that orchestrate male and female specific trait development, and JH acts as a mediator between nutrition and mandible growth. We found that the Cmdsx gene regulates sex differentiation in the stag beetle. Knockdown of Cmdsx by RNA-interference in both males and females produced intersex phenotypes, indicating a role for Cmdsx in sex-specific trait growth. By combining knockdown of Cmdsx with JH treatment, we showed that female-specific splice variants of Cmdsx contribute to the insensitivity of female mandibles to JH: knockdown of Cmdsx reversed this pattern, so that mandibles in knockdown females were stimulated to grow by JH treatment. In contrast, mandibles in knockdown males retained some sensitivity to JH, though mandibles in these individuals did not attain the full sizes of wild type males. We suggest that moderate JH sensitivity of mandibular cells may be the default developmental state for both sexes, with sex-specific Dsx protein decreasing sensitivity in females, and increasing it in males. This study is the first to demonstrate a causal link between the sex determination and JH signaling pathways, which clearly interact to determine the developmental fates and final sizes of nutrition-dependent secondary-sexual characters.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Many male animals wield ornaments or weapons of exaggerated proportions. We propose that increased cellular sensitivity to signaling through the insulin/insulin-like growth factor (IGF) pathway may ...be responsible for the extreme growth of these structures. We document how rhinoceros beetle horns, a sexually selected weapon, are more sensitive to nutrition and more responsive to perturbation of the insulin/IGF pathway than other body structures. We then illustrate how enhanced sensitivity to insulin/IGF signaling in a growing ornament or weapon would cause heightened condition sensitivity and increased variability in expression among individuals—critical properties of reliable signals of male quality. The possibility that reliable signaling arises as a by-product of the growth mechanism may explain why trait exaggeration has evolved so many different times in the context of sexual selection.
The elaborate ornaments and weapons of sexual selection, such as the vast array of horns observed in scarab beetles, are some of the most striking outcomes of evolution. How these novel traits have ...arisen, develop, and respond to condition is governed by a complex suite of interactions that require coordination between the environment, whole-animal signals, cell–cell signals, and within-cell signals. Endocrine factors, developmental patterning genes, and sex-specific gene expression have been shown to regulate beetle horn size, shape, and location, yet no overarching mechanism of horn shape has been described.
Recent advances in microscopy and computational analyses combined with a functional genetic approach have revealed that patterning genes combined with intricate epithelial folding and movement are responsible for the final shape of a beetle head horn.
The two-spotted spider mite,
Tetranychus urticae
Koch, is a constant threat to sustainable production of numerous economically important crops globally. Management of
T. urticae
is heavily reliant on ...the application of synthetic acaricides. However,
T. urticae
has rapidly developed resistance to most of the acaricides available for its control due to its very broad host plant range, extremely short lifecycle, high fecundity, arrhenotokous parthenogenesis, and overwintering strategy. Despite the recent progress in identifying genetic changes/markers associated with resistance toward some commonly used acaricides for
T. urticae
, there is still limited studies that select and apply these markers in field populations to guide sustainable pest management strategy design. Temporal and spatial characterization of acaricide-resistant phenotypes and their underlying mechanisms are crucial for the design and implementation of successful and sustainable integrated mite management programs. This review highlights the current acaricide resistance status of field-collected
T. urticae
populations and the underlying molecular mechanisms of resistance. Our review found that some genetic mutations in target sites and/or overexpression of metabolic genes confer resistance in geographically exclusive populations, while some resistance markers appear to be specific to populations at biogeographical areas. Thus, there is a need for locally based coordinated efforts to understand the mechanisms of resistance present in endemic
T. urticae
populations. Moreover, we discuss a prospective template for designing an effective acaricide resistance management program within various agroecosystems.
The increased urbanization of a growing global population makes imperative the development of sustainable integrated pest management (IPM) strategies for urban pest control. This emphasizes pests ...that are closely associated with the health and wellbeing of humans and domesticated animals. Concurrently there are regulatory requirements enforced to minimize inadvertent exposures to insecticides in the urban environment. Development of insecticide resistance management (IRM) strategies in urban ecosystems involves understanding the status and mechanisms of insecticide resistance and reducing insecticide selection pressure by combining multiple chemical and non-chemical approaches. In this review, we will focus on the commonly used insecticides and molecular and physiological mechanisms underlying insecticide resistance in six major urban insect pests: house fly, German cockroach, mosquitoes, red flour beetle, bed bugs and head louse. We will also discuss several strategies that may prove promising for future urban IPM programs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Among the most dramatic examples of sexual selection are the weapons used in battles between rival males over access to females. As with ornaments of female choice, the most “exaggerated” sexually ...selected weapons vary from male to male more widely than other body parts (hypervariability), and their growth tends to be more sensitive to nutritional state or physiological condition compared with growth of other body parts (“heightened” conditional expression). Here, we use RNAseq analysis to build on recent work exploring these mechanisms in the exaggerated weapons of beetles, by examining patterns of differential gene expression in exaggerated (head and thorax horns) and non‐exaggerated (wings, genitalia) traits in the Asian rhinoceros beetle, Trypoxylus dichotomus. Our results suggest that sexually dimorphic expression of weaponry involves large‐scale changes in gene expression, relative to other traits, while nutrition‐driven changes in gene expression in these same weapons are less pronounced. However, although fewer genes overall were differentially expressed in high‐ vs. low‐nutrition individuals, the number of differentially expressed genes varied predictably according to a trait's degree of condition dependence (head horn > thorax horn > wings > genitalia). Finally, we observed a high degree of similarity in direction of effects (vectors) for subsets of differentially expressed genes across both sexually dimorphic and nutritionally responsive growth. Our results are consistent with a common set of mechanisms governing sexual size dimorphism and condition dependence.
Abstract
Males of the Asian rhinoceros beetle, Trypoxylus dichotomus, possess exaggerated head and thoracic horns that scale dramatically out of proportion to body size. While RNAi-mediated ...knockdowns of the insulin receptor suggest that the insulin signaling pathway regulates nutrition-dependent growth including exaggerated horns, the genes that regulate disproportionate growth have yet to be identified. We used RNAi-mediated knockdown of several genes to investigate their potential role in growth and scaling of the sexually dimorphic, exaggerated head horns of T. dichotomus. Knockdown of the insulin signaling substrate chico and the ecdysone response element broad caused significant decreases in head horn length, while having no or minimal effects on other structures such as elytra and tibiae. However, scaling of horns to body size was not affected by either knockdown. In addition, knockdown of phosphatase and tensin homolog, a negative regulator of the insulin signaling pathway, had no significant effects on any trait. Our results do not identify any candidate genes that may specifically mediate the allometric aspect of horn growth, but they do confirm the insulin signaling pathway as a mediator of conditional trait expression, and importantly implicate the ecdysone signaling pathway, possibly in conjunction with insulin signaling, as an additional mediator of horn growth.
The two-spotted spider mite, Tetranychus urticae, is a polyphagous pest feeding on over 1100 plant species, including numerous highly valued economic crops. The control of T. urticae largely depends ...on the use of acaricides, which leads to pervasive development of acaricide resistance. Cytochrome P450-mediated metabolic detoxification is one of the major mechanisms of acaricide resistance in T. urticae. NADPH-cytochrome P450 reductase (CPR) plays as a crucial co-factor protein that donates electron(s) to microsomal cytochrome P450s to complete their catalytic cycle. This study seeks to understand the involvement of CPR/P450 in acaricide resistance in T. urticae. The full-length cDNA sequence of T. urticae's CPR (TuCPR) was cloned and characterized. TuCPR was ubiquitously transcribed in different life stages of T. urticae and the highest transcription was observed in the nymph and adult stages. TuCPR was constitutively over-expressed in six acaricide resistant populations compared to a susceptible one. TuCPR transcriptional expression was also induced by multiple acaricides in a time-dependent manner. Down-regulation of TuCPR via RNA interference (RNAi) in T. urticae led to reduced enzymatic activities of TuCPR and cytochrome P450s, as well as a reduction of resistance to multiple acaricides, abamectin, bifenthrin, and fenpyroximate. The outcome of this study highlights CPR as a potential novel target for eco-friendly control of T. urticae and other related plant-feeding pests.
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•Piperonyl butoxide (PBO) reduced abamectin, bifenthrin, and fenpyroximate resistance in T. urticae populations.•T. urticae's cytochrome P450 reductase (TuCPR) was cloned, sequenced and analyzed.•Abamectin, bifenthrin and fenpyroximate treatment induced TuCPR gene expression.•Silencing of TuCPR in T. urticae caused a reduction in acaricide resistance.
Many male animals have evolved exaggerated traits that they use in combat with rival males to gain access to females and secure their reproductive success. But some male animals invest in nuptial ...gifts that gains them access to females. Both these reproductive strategies are costly in that resources are needed to produce the weapon or nuptial gift. In closely related species where both weapons and nuptial gifts are present, little is known about the potential evolutionary trade-off faced by males that have these traits. In this study, we use dobsonflies (order Megaloptera, family Corydalidae, subfamily Corydalinae) to examine the presence and absence of enlarged male weapons versus nuptial gifts within and among species. Many dobsonfly species are sexually dimorphic, and males possess extremely enlarged mandibles that they use in battles, whereas in other species, males produce large nuptial gifts that increase female fecundity. In our study, we show that male accessory gland size strongly correlates with nuptial gift size and that when male weapons are large, nuptial gifts are small and vice versa. We mapped weapons and nuptial gifts onto a phylogeny we constructed of 57 species of dobsonflies. Our among-species comparison shows that large nuptial gift production evolved in many species of dobsonfly but is absent from those with exaggerated weapons. This pattern supports the potential explanation that the trade-off in resource allocation between weapons and nuptial gifts is important in driving the diversity of male mating strategies seen in the dobsonflies, whereas reduced male–male competition in the species producing large spermatophores could be an alternative explanation on their loss of male weapons. Our results shed new light on the evolutionary interplay of multiple sexually selected traits in animals.
Food quality is a critical environmental condition that impacts an animal’s growth and development. Many insects facing this challenge have evolved a phenotypically plastic, adaptive response. For ...example, many species of insect exhibit facultative wing growth, which reflects a physiological and evolutionary trade-off between dispersal and reproduction, triggered by environmental conditions. What the environmental cues are and how they are transduced to produce these alternative forms, and their associated ecological shift from dispersal to reproduction, remains an important unsolved problem in evolutionary ecology. In this study, we investigated the role that host quality has on the induction of wing development in a wing polyphenic insect exhibiting strong tradeoffs in investment between dispersal and reproduction, the brown planthopper, a serious rice pest in Asia. As rice plants grow, the short-winged brown planthopper dominates the population, but a shift occurs as the plants mature and senesce in the field such that long-winged brown planthoppers emerge and migrate. It remains unknown how changes in the rice plant induce development of the long-winged morph, despite recent discoveries on the role of the insulin and JNK signaling pathways in wing development. We found that by mimicking the glucose concentration of senescing rice plants, we significantly increased the proportion of long-winged female planthoppers. The effects of glucose on wing morph are additive with previously described effects of density. Our results show that host quality both directly regulates phenotypic plasticity and interacts with other factors such as density to produce the appropriate phenotype for specific environmental conditions.
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