Effects of dopamine on juvenile hormone metabolism and fitness in Drosophila virilis

Drosophila melanogaster Transcriptome Response to Different Wolbachia Strains

Wolbachia is a maternally inherited, intercellular bacterial symbiont of insects and some other invertebrates. Here, we investigated the effect of two different Wolbachia strains, differing in a large chromosomal inversion, on the differential expression of genes in D. melanogaster females. We revealed significant changes in the transcriptome of the infected flies compared to the uninfected ones, as well as in the transcriptome of flies infected with the Wolbachia strain, wMelPlus, compared to flies infected with the wMelCS112 strain. We linked differentially expressed genes (DEGs) from two pairwise comparisons, "uninfected-wMelPlus-infected" and "uninfected-wMelCS112-infected", into two gene networks, in which the following functional groups were designated: "Proteolysis", "Carbohydrate transport and metabolism", "Oxidation-reduction process", "Embryogenesis", "Transmembrane transport", "Response to stress" and "Alkaline phosphatases". Our data emphasized similarities and differences between infections by different strains under study: a wMelPlus infection results in more than double the number of upregulated DEGs and half the number of downregulated DEGs compared to a wMelCS112 infection. Thus, we demonstrated that Wolbachia made a significant contribution to differential expression of host genes and that the bacterial genotype plays a vital role in establishing the character of this contribution.

Prodigiosin from Serratia rubidaea MJ 24 impedes Helicoverpa armigera development by the dysregulation of Juvenile hormone-dopamine system

Prodigiosin pigment is a secondary metabolite produced by many bacterial species and is known for its medicinal properties. A few of these prodigiosin-producing bacteria are also reported to be entomopathogenic. It is intriguing to unravel the role of prodigiosin in insecticidal activities and its mode of action. In this study, we have shown the production and characterization of prodigiosin from the Serratia rubidaea MJ 24 isolated from the soil of the Western Ghats, India. Further, we assessed the effect of this pigment on the lepidopteran agricultural pest, Helicoverpa armigera. Prodigiosin-fed H. armigera indicated defective development of insect growth upon treatment. Due to defective early development, about 50% mortality and 40% reduction in body weight were observed in insects fed on a 500 ppm prodigiosin-containing diet. The transcriptomic analysis of these insects indicated significant dysregulation of Juvenile hormone synthesis and response related genes. In addition, dopamine related processes and their resultant melanization and sclerotization processes were also found to be affected. The changes in the expression levels of the key transcripts were further validated using real-time quantitative PCR. The metabolome data confirmed the developmental dysregulation of precursors and products of differentially regulated genes due to prodigiosin. Therefore, the corroborated data suggests that prodigiosin majorly affects H. armigera development through dysregulation of the Juvenile hormone-dopamine system and can be considered as a bioactive scaffold to design insect-pest management compounds. This study provides the first report of in-depth analysis of insecticidal system dynamics in H. armigera insects upon prodigiosin feeding via gene expression and metabolic change via omics approach.

Population density modulates insect progenitive plasticity through the regulation of dopamine biosynthesis

Insect fecundity is a quantitative phenotype strongly affected by genotypes and the environment. However, interactions between genotypes and environmental factors in modulating insect fecundity remain largely unknown. This study investigated the impact of population density on the fecundity of Nilaparvata lugens (brown planthopper; BPH) carrying homozygous high- (HFG) or low- (LFG) fecundity homozygous genotypes. Under low population densities, the fecundity and population growth rate of both genotypes showed similar increasing trends across generations, while the trends between HFG and LFG under high population densities were opposite. Through a combination of temporal analysis and weighted gene co-expression network analyses on RNA-seq data of HFG and LFG under low and high population densities in the 1st, 3rd, and 5th generations, we identified 2 gene modules that were associated with these density-dependent progenitive phenotypes. Four pathways related to the neural system were simultaneously enriched by the 2 gene modules. Furthermore, Nlpale, which encodes a tyrosine hydroxylase, was identified as a key gene. The RNA interference of this gene and manipulation of its downstream product dopamine significantly affected the basic and density-dependent progenitive phenotypes of BPH. These findings indicated that dopamine biosynthesis is the key regulatory factor that determines fecundity in response to density changes in different BPH genotypes. Thus, this study provides insights into the interaction of a typical environmental factor and insect genotype during the process of population regulation.

Environmentally responsive reproduction: neuroendocrine signalling and the evolution of eusociality

Eusociality is a rare but successful life-history strategy that is defined by the reproductive division of labour. In eusocial species, most females forgo their own reproduction to support that of a dominant female or queen. In many eusocial insects, worker reproduction is inhibited via dominance hierarchies or by pheromones produced by the queen and her brood. Here, we consider whether these cues may act as generic 'environmental signals', similar to temperature or nutrition stress, which induce a state of reproductive dormancy in some solitary insects. We review the recent findings regarding the mechanisms of reproductive dormancy in insects and highlight key gaps in our understanding of how environmental cues inhibit reproduction.

Juvenile Hormone Studies in Drosophila melanogaster

In the field of insect endocrinology, juvenile hormone (JH) is one of the most wondrous entomological terms. As a unique sesquiterpenoid hormone produced and released by the endocrine gland, corpus allatum (CA), JH is a critical regulator in multiple developmental and physiological processes, such as metamorphosis, reproduction, and behavior. Benefited from the precise genetic interventions and simplicity, the fruit fly, Drosophila melanogaster, is an indispensable model in JH studies. This review is aimed to present the regulatory factors on JH biosynthesis and an overview of the regulatory roles of JH in Drosophila. The future directions of JH studies are also discussed, and a few hot spots are highlighted.

Antidepressant sertraline impairs the induced morphological defense of Ceriodaphnia cornuta in response to Chaoborus larvae kairomone

Antidepressants discharged into natural waters are likely to become a new type of endocrine pollutant, which may impact the interspecific relationship in aquatic ecosystem. Induced defense of cladocerans plays an important role in maintaining the balance of interspecific relationships between cladocerans and higher trophic levels. Here we studied the effects of antidepressant sertraline, a selective serotonin reuptake inhibitor, on the induced defensive traits of Ceriodaphnia cornuta in response to invertebrate predator Chaoborus larvae kairomone, including morphological defense and life history traits. We also conducted the predation experiments to check the selection rate of Chaoborus larvae during directly ingesting C. cornuta that were exposed to Chaoborus larvae kairomone at high concentration of sertraline. Results showed sertraline had an interference effect on the induced morphological defense of C. cornuta in response to Chaoborus larvae kairomone, i.e. the high concentration of sertraline (20 and 100 μg L^-1) significantly reduced the horns induction. However, the different concentrations of sertraline generally did not affect the life history traits of C. cornuta, regardless of presence or absence of Chaoborus larvae kairomone. The predation experiment demonstrated that the inhibition of sertraline on the induced morphological defense of C. cornuta can promote the feeding selective efficiency of Chaoborus larvae, and thus cause C. cornuta easily to be predated by Chaoborus larvae. Our results suggested that sertraline at the concentrations that are not direct harmful to life history traits of C. cornuta can seriously affect the predator-prey relationship, indicating that effects of pollutants on interspecific relationships should be considered comprehensively to avoid underestimating the potential risk of pollutants to ecosystems.

The effect of mild heat stress of different frequencies on the adaptability of Drosophila melanogaster females

In natural populations, insects regularly face an adverse impact of different natures: harsh weather swings, lack of food resources, the insecticidal treatment. We studied the effect of repeated episodes of mild heat stress of different frequencies on stress resistance of Drosophila melanogaster females. We found out that the mild heat stress (38°С, 1 hr) repeated daily within 2 weeks resulted in (a) an increased activity of the dopamine (DA) metabolism enzymes, DA-dependent arylalkylamine N-acetyltransferase and alkaline phosphatase, which suggested a decrease in DA level, and (b) an increased survival rate under acute heat stress (38°С, 4 hr). The same mild heat stress repeated weekly had no effect on these parameters.

Transcriptome analysis of hemocytes from the white shrimp Litopenaeus vannamei with the injection of dopamine

As a crucial neuroendocrine-immune factor, dopamine (DA) could regulate the immune system of Litopenaeus vannamei. To understand the immune mechanisms and regulatory pathways of DA in L. vannamei, the transcriptome analysis of hemocytes of L. vannamei with injection of DA (10^-6 mol/shrimp) at 3 and 12 h were performed in this study. Moreover, quantitative real-time PCR (qPCR) method was applied to validate the accuracy of transcriptome sequencing and analyze the expression pattern of candidate differentially expressed genes (DEGs) at different time points (0, 3, 6, 12, and 24 h) after DA injection. The results showed that a total of 51382 unigenes with a N50 length of 2341 bp were generated. And 1397 and 457 DEGs were obtained by comparative transcriptome at 3 and 12h respectively. Moreover, the results of functional annotation and enriched pathway showed that the DEGs were involved in phagosome (ko04145), lysosome (ko04142), Endocytosis (ko04144), and NOD-like receptor signaling pathway (ko04621). Besides, the Pearson's correlation coefficient (R) between transcriptome sequencing and qPCR was 0.845, which confirmed the reliability of the transcriptome sequencing results and the accuracy of assembly. Furthermore, the expression pattern of 15 candidate DEGs, containing 9 up-regulated and 6 down-regulated DEGs at 3 h, indicated the regulation of DA in physiological functions especially in the immune system. Therefore, these results revealed that DA induced the expressions of membrane receptors or proteins, activated intracellular signaling pathways, regulated cellular and humoral immune systems, controlled antioxidation and apoptosis, and was involved in the regulation of neuroendocrine system. These findings are helpful to promote the understanding on the effects of biogenic amines on physiological functions and regulatory networks of crustacean, and offer a substantial material and foundation for researching the immune response of crustacean.

Chlorpyrifos Exposure Induces Parkinsonian Symptoms and Associated Bone Loss in Adult Swiss Albino Mice

Prenatal and early life exposure of chlorpyrifos (CPF), a widely used pesticide, is known to cause neuronal deficits and Parkinson's disease (PD). However, data about the effect of its exposure at adult stages on PD-like symptoms and associated bone loss is scanty. In the present study, we investigated the impact of CPF on the behavioral alterations seen in PD using adult Swiss albino mice. PD is often associated with bone loss. Hence, skeletal changes were also evaluated using micro-computed tomography and histology. MPTP was used as a positive control. Cell culture studies using MC3T3E-1, SHSY5Y, and primary osteoclast cultures were done to understand the cellular mechanism for the behavioral and skeletal changes. Our results showed that CPF treatment leads to PD-like symptoms due to the loss of dopaminergic neurons. Moreover, CPF has a deleterious effect on the trabecular bone through both indirect changes in circulating factors and direct stimulation of multinucleate osteoclast cell formation. The impact on the bone mass was even stronger than MPTP. In conclusion, this is the first report demonstrating that CPF induces parkinsonian features in adult Swiss albino mice and it is accompanied by loss of trabecular bone.

Pleiotropic Effects of ebony and tan on Pigmentation and Cuticular Hydrocarbon Composition in Drosophila melanogaster

Pleiotropic genes are genes that affect more than one trait. For example, many genes required for pigmentation in the fruit fly Drosophila melanogaster also affect traits such as circadian rhythms, vision, and mating behavior. Here, we present evidence that two pigmentation genes, ebony and tan, which encode enzymes catalyzing reciprocal reactions in the melanin biosynthesis pathway, also affect cuticular hydrocarbon (CHC) composition in D. melanogaster females. More specifically, we report that ebony loss-of-function mutants have a CHC profile that is biased toward long (>25C) chain CHCs, whereas tan loss-of-function mutants have a CHC profile that is biased toward short (<25C) chain CHCs. Moreover, pharmacological inhibition of dopamine synthesis, a key step in the melanin synthesis pathway, reversed the changes in CHC composition seen in ebony mutants, making the CHC profiles similar to those seen in tan mutants. These observations suggest that genetic variation affecting ebony and/or tan activity might cause correlated changes in pigmentation and CHC composition in natural populations. We tested this possibility using the Drosophila Genetic Reference Panel (DGRP) and found that CHC composition covaried with pigmentation as well as levels of ebony and tan expression in newly eclosed adults in a manner consistent with the ebony and tan mutant phenotypes. These data suggest that the pleiotropic effects of ebony and tan might contribute to covariation of pigmentation and CHC profiles in Drosophila.

Bone loss in MPTP mouse model of Parkinson's disease is triggered by decreased osteoblastogenesis and increased osteoclastogenesis

Bone loss is a non-motor symptom of Parkinson's disease (PD). It is unclear whether a patient's immobility or the endocrine changes in the body causes bone deterioration. To address this issue, we used an animal model of the disease where Swiss albino mice were injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on day 1 and were left untreated for eight weeks. Behavioral phenotypes of PD, and striatal acetylcholinesterase and dopamine levels were measured. Cortical and trabecular bones were assessed by μ-CT and histology. Gene expression studies were done through quantitative real-time PCR. Effect of MPP+ and MPTP-treated mice serum on MC3T3E-1, SH-SY5Y, and primary osteoclast cells were also studied. Our results demonstrated that MPTP treatment leads to PD like symptoms. It shows a loss of trabecular bone mass and quality by decreasing osteoblast and increased osteoclast number and activity. This effect was accompanied by reduced osteogenic and elevated osteoclastogenic genes expression. While MPP+ had a cytotoxic effect on dopaminergic neurons, it did not affect bone cells. However, ex-vivo treatment of the serum from MPTP-treated mice decreased osteoblastogenesis and increased osteoclastogenesis in cell culture. In conclusion, our study suggests that MPTP-induced parkinsonian features in mice leads to trabecular bone loss by decreased bone formation and increased bone resorption due to changes in the serum circulating factors. This study characterizes the microarchitectural and cellular changes in the skeleton of a mouse model of PD that can be further utilized to investigate therapeutic avenues to treat bone loss in PD patients.

The role of insulin signalling in the endocrine stress response in Drosophila melanogaster: A mini-review

The endocrine stress response in Drosophila includes catecholamines, juvenile hormone (JH), 20-hydroxyecdysone (20E) and the insulin/insulin-like growth factor signalling pathway (IIS). Several changes in the IIS and hormonal status that occur under unfavourable conditions are universal and do not depend on the nature of stress exposure. The reviewed studies on the impact of different element of the Drosophila IIS, such as insulin-like receptor, the homologue of its substrate, CHICO, the transcription factor dFOXO and insulin like peptide 6, on the hormonal status suggest that the IIS controls catecholamine metabolism indirectly via JH, and there is a feedback loop in the interaction of JH and IIS. Moreover, at least one of the ways in which the IIS is involved in the control of stress resistance is mediated through JH/dopamine signalling.

Various Wolbachia genotypes differently influence host Drosophila dopamine metabolism and survival under heat stress conditions

BACKGROUND

One of the most widespread prokaryotic symbionts of invertebrates is the intracellular bacteria of Wolbachia genus which can be found in about 50% of insect species. Wolbachia causes both parasitic and mutualistic effects on its host that include manipulating the host reproductive systems in order to increase their transmission through the female germline, and increasing the host fitness. One of the mechanisms, promoting adaptation in biological organisms, is a non-specific neuroendocrine stress reaction. In insects, this reaction includes catecholamines, dopamine, serotonin and octopamine, which act as neurotransmitters, neuromodulators and neurohormones. The level of dopamine metabolism correlates with heat stress resistance in Drosophila adults.

RESULTS

To examine Wolbachia effect on Drosophila survival under heat stress and dopamine metabolism we used five strains carrying the nuclear background of interbred Bi90 strain and cytoplasmic backgrounds with different genotype variants of Wolbachia (produced by 20 backcrosses of Bi90 males with appropriate source of Wolbachia). Non-infected Bi90 strain (treated with tetracycline for 3 generations) was used as a control group. We demonstrated that two of five investigated Wolbachia variants promote changes in Drosophila heat stress resistance and activity of enzymes that produce and degrade dopamine, alkaline phosphatase and dopamine-dependent arylalkylamine N-acetyltransferase. What is especially interesting, wMelCS genotype of Wolbachia increases stress resistance and the intensity of dopamine metabolism, whereas wMelPop strain decreases them. wMel, wMel2 and wMel4 genotypes of Wolbachia do not show any effect on the survival under heat stress or dopamine metabolism. L-DOPA treatment, known to increase the dopamine content in Drosophila, levels the difference in survival under heat stress between all studied groups.

CONCLUSIONS

The genotype of symbiont determines the effect that the symbiont has on the stress resistance of the host insect.

Endocrine network essential for reproductive success in Drosophila melanogaster

Ecdysis-triggering hormone (ETH) was originally discovered and characterized as a molt termination signal in insects through its regulation of the ecdysis sequence. Here we report that ETH persists in adult Drosophila melanogaster, where it functions as an obligatory allatotropin to promote juvenile hormone (JH) production and reproduction. ETH signaling deficits lead to sharply reduced JH levels and consequent reductions of ovary size, egg production, and yolk deposition in mature oocytes. Expression of ETH and ETH receptor genes is in turn dependent on ecdysone (20E). Furthermore, 20E receptor knockdown specifically in Inka cells reduces fecundity. Our findings indicate that the canonical developmental roles of 20E, ETH, and JH during juvenile stages are repurposed to function as an endocrine network essential for reproductive success.

Disruption of dopamine homeostasis has sexually dimorphic effects on senescence characteristics of Drosophila melanogaster

The neurotransmitter dopamine (DA) is known to be involved in a multitude of physiological processes. We investigated sexually dimorphic effects of disruptions in DA homeostasis and its relationship to senescence using three different Drosophila melanogaster mutants namely Catsup (Catsup²⁶ ) with elevated DA levels, and pale (ple² ), Punch (Pu^Z22 ) with depleted DA levels. In all genotypes including controls, DA levels were significantly lower in old (45-50-day-old) flies compared with young (3-5-day-old) in both sexes. Interestingly, females had lower DA content than males at young age whereas this difference was not observed in old age, suggesting that males had a larger decline in DA levels with age. Females, in general, were longer lived compared with males in all genotypes except ple² mutants with depleted DA levels. This phenotype was abolished in the ple² rescue flies. Interestingly, females also demonstrated marked age-related decline in circadian locomotor activity compared with males. Old Catsup²⁶ males with elevated DA levels accumulated significantly lower levels of lipid peroxidation product 4-hydroxy 2-nonenal (4-HNE) compared with age-matched wild type, ple² and Pu^Z22 mutant males. In Catsup²⁶ revertant lines this phenomenon was absent. We also observed a sexually dimorphic response in the expression levels of key stress and aging associated and/or related transcription factor genes across genotypes with elevated or depleted DA levels which was reverted to wild type levels in specific rescue lines. Taken together, our results reveal a novel sexually dimorphic involvement of DA in senescence characteristics of D. melanogaster.

Australian black field crickets show changes in neural gene expression associated with socially-induced morphological, life-history, and behavioral plasticity

BACKGROUND

Ecological and evolutionary model organisms have provided extensive insight into the ecological triggers, adaptive benefits, and evolution of life-history driven developmental plasticity. Despite this, we still have a poor understanding of the underlying genetic changes that occur during shifts towards different developmental trajectories. The goal of this study is to determine whether we can identify underlying gene expression patterns that can describe the different life-history trajectories individuals follow in response to social cues of competition. To do this, we use the Australian black field cricket (Teleogryllus commodus), a species with sex-specific developmental trajectories moderated by the density and quality of calls heard during immaturity. In this study, we manipulated the social information males and females could hear by rearing individuals in either calling or silent treatments. We next used RNA-Seq to develop a reference transcriptome to study changes in brain gene expression at two points prior to sexual maturation.

RESULTS

We show accelerated development in both sexes when exposed to calling; changes were also seen in growth, lifespan, and reproductive effort. Functional relationships between genes and phenotypes were apparent from ontological enrichment analysis. We demonstrate that increased investment towards traits such as growth and reproductive effort were often associated with the expression of a greater number of genes with similar effect, thus providing a suite of candidate genes for future research in this and other invertebrate organisms.

CONCLUSIONS

Our results provide interesting insight into the genomic underpinnings of developmental plasticity and highlight the potential of a genomic exploration of other evolutionary theories such as condition dependence and sex-specific developmental strategies.

Dopamine is a key regulator in the signalling pathway underlying predator-induced defences in Daphnia

The waterflea Daphnia is a model to investigate the genetic basis of phenotypic plasticity resulting from one differentially expressed genome. Daphnia develops adaptive phenotypes (e.g. morphological defences) thwarting predators, based on chemical predator cue perception. To understand the genomic basis of phenotypic plasticity, the description of the precedent cellular and neuronal mechanisms is fundamental. However, key regulators remain unknown. All neuronal and endocrine stimulants were able to modulate but not induce defences, indicating a pathway of interlinked steps. A candidate able to link neuronal with endocrine responses is the multi-functional amine dopamine. We here tested its involvement in trait formation in Daphnia pulex and Daphnia longicephala using an induction assay composed of predator cues combined with dopaminergic and cholinergic stimulants. The mere application of both stimulants was sufficient to induce morphological defences. We determined dopamine localization in cells found in close association with the defensive trait. These cells serve as centres controlling divergent morphologies. As a mitogen and sclerotization agent, we anticipate that dopamine is involved in proliferation and structural formation of morphological defences. Furthermore, dopamine pathways appear to be interconnected with endocrine pathways, and control juvenile hormone and ecdysone levels. In conclusion, dopamine is suggested as a key regulator of phenotypic plasticity.

Phenotypic plasticity in three Daphnia genotypes in response to predator kairomone: evidence for an involvement of chitin deacetylases

The genetic background of inducible morphological defences in Daphnia is still largely unknown. Dissolved infochemicals from the aquatic larvae of the phantom midge Chaoborus induce so called ‘neck-teeth’ in the first three postembryonic stages of Daphnia pulex. This defence has become a textbook example for inducible defences. In a target gene approach, by applying a gradient of three Daphnia genotypes which differed significantly in neck-teeth induction in response to equal amounts of kairomone, we report a high correlation of neck-teeth induction in D. pulex and relative gene expression of two chitin deacetylases. Further, previous studies suggested genes from both the juvenoid and the insulin hormone signalling pathways as well as several morphogenetic genes downstream to be responsible for the neck-teeth induction in D. pulex. However, these data on previously suggested genes reported were not supported by this study. None of the three D. pulex clones did show an upregulation of these previously proposed candidate genes tested in this study as a response to predator kairomone, which is interpreted as the result of refined methods used for both RNA sampling and kairomone enrichment, which yielded unambiguous results compared to earlier studies. The assessment of a clonal gradient of Daphnia in the presence and absence of infochemicals provides a promising approach to identify further genes being involved in the induction of morphological defences by correlating gene expression and morphology.

Antioxidant and neuroprotective potential of chitooligomers in Caenorhabditis elegans exposed to Monocrotophos

The objectives of this investigation were to establish the propensity of the chitooligomers (COS) to ameliorate neurodegeneration and oxidative stress in Caenorhabditis elegans induced by an organophosphorus insecticide, Monocrotophos (MCP). COS was prepared from α-chitosan by the enzymatic method using chitosanase and characterized by HPLC and electron spray ionization-TOF-(ESI-TOF)-MS. We exposed age synchronized L4 C. elegans worms (both wild type N2 and transgenic strain BZ555 (Pdat-1:GFP) to sublethal concentration of MCP (0.75mM) for 24h in the presence or absence of COS (0.2mM). The neuroprotective effect of COS was examined in N2 worms in terms of brood size, lifespan, egg laying, dopamine content, acetylcholinesterase and carboxylesterase activity and by direct visualization and quantification of degeneration of dopaminergic neurons in BZ555. Exposure to COS extended lifespan, normalized egg laying, increased brood size, decreased the dopaminergic neurodegeneration, increased the dopamine content and increased AChE and carboxylesterase activity in C. elegans treated with MCP. COS induced a significant decrease in reactive oxygen species and increased the reduced glutathione level as well as increased superoxide dismutase and catalase activity. Our findings demonstrate that COS significantly inhibits the dopaminergic neurodegeneration and associated physiological alterations induced by MCP in C. elegans by attenuating the oxidative stress as well.

Effect of monocrotophos, an organophosphorus insecticide, on the striatal dopaminergic system in a mouse model of Parkinson’s disease

Our earlier study had shown that low concentrations of monocrotophos (MCP) elicited dopaminergic features of Parkinson’s disease (PD) in the nematode Caenorhabditis elegans. In the present study, the effect of low doses of MCP on the striatal dopaminergic neurons was investigated using the mouse model system. MCP was initially screened for its ability to cause any neurobehavioral deficits and alterations in the dopaminergic system in Swiss albino mice, aged 8 weeks and weighing 25–30 g, with repeated doses at 0.3 and 0.6 mg/kg body weight (b.w.)/day for 7 days and 30 days. Mice were treated with four intraperitoneal injections for every 2 h with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at the dosage of 14 mg/kg b.w. MCP was administered to these mice at the above-mentioned doses for 7 days. Mice administered with MCP alone revealed a significant ( p < 0.05) reduction in the dopamine (DA) content at both 7 and 30 days and showed a significant ( p < 0.05) increase in neurobehavioral deficits. Interestingly, when MCP was administered for 7 days to MPTP-treated mice, further significant decrease in both DA content and increase in neurobehavioral deficits were apparent. The extent of reactive oxygen species and lipid peroxidation were markedly increased, while the ratio of reduced to oxidized glutathione levels were significantly decreased ( p < 0.05) in the treated mice as compared to the control. Significant histopathological alterations and a marked reduction in the number of tyrosine hydroxylase positive cells were evident in striatum of mice treated with higher doses of MCP. These changes were comparable to that seen in mice treated with MPTP and post-administered lower doses of MCP. Our findings suggest that MCP per se has the propensity to induce pathological changes in the dopaminergic neurons as well as augment the degeneration in a compromised nigrostriatal system such as that in PD.

Characterization of an invertebrate-type dopamine receptor of the American cockroach, Periplaneta americana

We have isolated a cDNA coding for a putative invertebrate-type dopamine receptor (Peadop2) from P. americana brain by using a PCR-based strategy. The mRNA is present in samples from brain and salivary glands. We analyzed the distribution of the PeaDOP2 receptor protein with specific affinity-purified polyclonal antibodies. On Western blots, PeaDOP2 was detected in protein samples from brain, subesophageal ganglion, thoracic ganglia, and salivary glands. In immunocytochemical experiments, we detected PeaDOP2 in neurons with their somata being located at the anterior edge of the medulla bilaterally innervating the optic lobes and projecting to the ventro-lateral protocerebrum. In order to determine the functional and pharmacological properties of the cloned receptor, we generated a cell line constitutively expressing PeaDOP2. Activation of PeaDOP2-expressing cells with dopamine induced an increase in intracellular cAMP. In contrast, a C-terminally truncated splice variant of this receptor did not exhibit any functional property by itself. The molecular and pharmacological characterization of the first dopamine receptor from P. americana provides the basis for forthcoming studies focusing on the significance of the dopaminergic system in cockroach behavior and physiology.

Brain norepinephrine identified by mass spectrometry is associated with reproductive status of females of the linden bug Pyrrhocoris apterus

Several biogenic amines, including controversial presence of norepinephrine (NE), were identified by the high performance liquid chromatography equipped with electrospray ionisation mass spectrometry in brain complexes of adult females of Pyrrhocoris apterus. Quantitative analysis was performed by the high performance liquid chromatography coupled to electrochemical detector. Levels of NE, dopamine (DA), octopamine (OA) and 5-hydroxytryptamine (5-HT) in brain complexes were measured in reproductive vs. diapause females. In field collected samples, levels of NE and DA were significantly higher in reproductive (May) than in non-reproductive (Sep, Oct, Feb) females. In laboratory females, NE is higher in long day photoperiod (reproduction) than in short day photoperiod (diapause) already from the first week of the adult age, while DA shows differences between the two contrasting photoperiods only from the second week of the adult age. No association between reproductive status and levels of OA and 5-HT was found.

Early manipulation of juvenile hormone has sexually dimorphic effects on mature adult behavior in Drosophila melanogaster

Hormones are critical for the development, maturation, and maintenance of physiological systems; therefore, understanding their involvement during maturation of the brain is important for the elucidation of mechanisms by which adults become behaviorally competent. Changes in exogenous and endogenous factors encountered during sexual maturation can have long lasting effects in mature adults. In this study, we investigated the role of the gonadotropic hormone, juvenile hormone (JH), in the modulation of adult behaviors in Drosophila. Here we utilized methoprene (a synthetic JH analog) and precocene (a JH synthesis inhibitor) to manipulate levels of JH in sexually immature male and female Drosophila with or without decreased synthesis of neuronal dopamine (DA). Locomotion and courtship behavior were assayed once the animals had grown to sexual maturity. The results demonstrate a sexually dimorphic role for JH in the modulation of these centrally controlled behaviors in mature animals that is dependent on the age of the animals assayed, and present DA as a candidate neuronal factor that differentially interacts with JH depending on the sex of the animal. The data also suggest that JH modulates these behaviors through an indirect mechanism. Since gonadotropic hormones and DA interact in mammals to affect brain development and later function, our results suggest that this mechanism for the development of adult behavioral competence may be evolutionarily conserved.

Role of D1- and D2-like receptors in age-specific regulation of juvenile hormone and 20-hydroxyecdysone levels by dopamine in Drosophila

In Drosophila females, the precursor of 20-hydroxyecdysone (20E), ecdysone, is synthesized in the ovary follicular cells. Juvenile hormone (JH) is synthesized de novo in the specialized endocrine gland, corpus allatum (CA); JH degradation is carried out by the enzymes synthesized in the fat body (FB). Earlier we have shown that in Drosophila females, dopamine up- or down-regulates 20E and JH levels depending on the developmental stage. The present study focuses on the role of D1- and D2-like receptors in the age-specific regulation of 20E and JH metabolism by dopamine. We show that in Drosophila melanogaster females D1- and D2-like receptor genes (DopR and DD2R accordingly) are expressed in CA and FB, but not in follicular cells. The level of DopR expression in CA is much higher in the young than in the mature females, whereas DD2R expression is much higher in the mature than in the young females. The DopR and DD2R expression patterns in FB are opposite to those observed in CA. In addition, we obtained data suggesting that the age-specific changes of DopR and DD2R expression in FB are under the control of 20E.

Fine-scale mapping of natural variation in fly fecundity identifies neuronal domain of expression and function of an aquaporin

To gain insight into the molecular genetic basis of standing variation in fitness related traits, we identify a novel factor that regulates the molecular and physiological basis of natural variation in female Drosophila melanogaster fecundity. Genetic variation in female fecundity in flies derived from a wild orchard population is heritable and largely independent of other measured life history traits. We map a portion of this variation to a single QTL and then use deficiency mapping to further refine this QTL to 5 candidate genes. Ubiquitous expression of RNAi against only one of these genes, an aquaporin encoded by Drip, reduces fecundity. Within our mapping population Drip mRNA level in the head, but not other tissues, is positively correlated with fecundity. We localize Drip expression to a small population of corazonin producing neurons located in the dorsolateral posterior compartments of the protocerebrum. Expression of Drip–RNAi using both the pan-neuronal ELAV-Gal4 and the Crz-Gal4 drivers reduces fecundity. Low-fecundity RILs have decreased Crz expression and increased expression of pale, the enzyme encoding the rate-limiting step in the production of dopamine, a modulator of insect life histories. Taken together these data suggest that natural variation in Drip expression in the corazonin producing neurons contributes to standing variation in fitness by altering the concentration of two neurohormones.

A major goal of modern evolutionary biology is to elucidate the genetic basis of standing genetic variation underlying fitness traits. This goal is important for a comprehensive picture of the evolutionary process, because it allows us to understand the mode of natural selection on fitness traits and identify the molecular and physiological processes that affect fitness traits. Here, we describe our work to identify the molecular genetic and physiological basis for natural variation in a core life history trait, fecundity, of Drosophila melanogaster. Using a variety of mapping techniques, we show that differential expression of the aquaporin Drip in nervous tissue affects natural variation in female fecundity. We further go on to describe a novel domain of expression of Drip in neurons that produce the insect stress hormone corazonin and demonstrate that differential expression of Drip in these neurons affects female fecundity putatively through modulating the concentration of corazonin and dopamine. This surprising and novel observation highlights the benefit of exploiting natural genetic variation to identify the molecular processes underlying phenotypic traits.

Downregulation of the dopamine D2-like receptor in corpus allatum affects juvenile hormone synthesis in Drosophila melanogaster females

In Drosophila, juvenile hormone (JH) is synthesized de novo in the specialized endocrine gland, corpusallatum (CA). Dopamine (DA) controls JH levels by either stimulating or inhibiting its synthesis and degradation depending on the developmental stage. The present study focuses on the role of D2-like receptors in the regulation of JH synthesis by dopamine. We show that D2-like receptors (DD2R) are expressed in CA cells of Drosophila melanogaster females. In addition, the level of JH production was analyzed in D. melanogaster females with decreased DD2R expression in CA (vs. corresponding control flies) by assessing multiple indices of JH synthesis (JH-hydrolyzing activity and stress reactivity of the system of JH metabolism, activity and stress reactivity of the alkaline phosphatase, activity and stress reactivity of the tyrosine decarboxylase). The differential value obtained for each index suggests increased JH production in female flies that downregulate DD2R. Based on these findings, we postulate that the DA inhibiting effect on the JH synthesis in D. melanogaster is mediated at least in part via D2-like receptors.

Mechanisms of age-specific regulation of dopamine metabolism by juvenile hormone and 20-hydroxyecdysone in Drosophila females

20-hydroxyecdysone (20E) and the juvenile hormone (JH) have an age-specific effect on total dopamine (DA) content in Drosophila (Gruntenko and Rauschenbach 2008). Earlier we studied the mechanism of influence of 20E and JH on DA metabolism in young females (Rauschenbach et al. in J Insect Physiol 53:587-591, 2007a: Arch Insect Biochem Physiol 65:95-102, 2008a; Gruntenko et al. in Arch Insect Biochem Physiol 72:263-269, 2009). Here we investigate the effects of 20E and JH on the activities of the alkaline phosphatase (ALP), tyrosine hydroxylase (TH) and DA-dependent arylalkylamine N-acetyltransferase (AANAT) in mature females of wild type D. virilis under normal conditions and under heat stress (38°C). 20E feeding of the flies led to a substantial decrease in ALP and TH activities and to an increase in AANAT activity in mature females. JH application resulted in an increasing of ALP and TH activities, but did not influence AANAT activity in mature females. A rise in JH and 20E levels was found to change ALP and TH stress reactivities. Mechanisms of age-specific regulation of DA level by 20E and JH in Drosophila females are discussed.

Dietary modulation of Drosophila sleep-wake behaviour

Background

A complex relationship exists between diet and sleep but despite its impact on human health, this relationship remains uncharacterized and poorly understood. Drosophila melanogaster is an important model for the study of metabolism and behaviour, however the effect of diet upon Drosophila sleep remains largely unaddressed.

Methodology/Principal Findings

Using automated behavioural monitoring, a capillary feeding assay and pharmacological treatments, we examined the effect of dietary yeast and sucrose upon Drosophila sleep-wake behaviour for three consecutive days. We found that dietary yeast deconsolidated the sleep-wake behaviour of flies by promoting arousal from sleep in males and shortening periods of locomotor activity in females. We also demonstrate that arousal from nocturnal sleep exhibits a significant ultradian rhythmicity with a periodicity of 85 minutes. Increasing the dietary sucrose concentration from 5% to 35% had no effect on total sucrose ingestion per day nor any affect on arousal, however it did lengthen the time that males and females remained active. Higher dietary sucrose led to reduced total sleep by male but not female flies. Locomotor activity was reduced by feeding flies Metformin, a drug that inhibits oxidative phosphorylation, however Metformin did not affect any aspects of sleep.

Conclusions

We conclude that arousal from sleep is under ultradian control and regulated in a sex-dependent manner by dietary yeast and that dietary sucrose regulates the length of time that flies sustain periods of wakefulness. These findings highlight Drosophila as an important model with which to understand how diet impacts upon sleep and wakefulness in mammals and humans.

20-hydroxyecdysone and juvenile hormone influence tyrosine hydroxylase activity in Drosophila females under normal and heat stress conditions

The effects of exogenous 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the tyrosine hydroxylase (TH), the first and rate-limiting DA biosynthetic enzyme, has been studied in young females of wild type D. virilis and D. melanogaster under normal conditions and under heat stress (38 degrees C). Both 20E feeding of the flies and JH application led to a substantial rise in TH activity. A rise in JH and 20E levels was found not to prevent the response of TH to heat stress, but to change the intensity of its response to the stress exposure. Putative mechanisms of regulation of DA level by 20E and JH in Drosophila females are discussed.

Immunogenic males: a genome-wide analysis of reproduction and the cost of mating in Drosophila melanogaster females

In Drosophila melanogaster, mating radically transforms female physiology and behaviour. Post-mating responses include an increase in the oviposition rate, a reduction in female receptivity and an activation of the immune system. The fitness consequences of mating are similarly dramatic--females must mate once in order to produce fertile eggs, but additional matings have a clear negative effect. Previously, microarrays have been used to examine gene expression of females differing in their reproductive status with the aim of identifying genes influenced by mating. However, as only virgin and single mated females were compared, transcriptional changes associated with reproduction (under natural selection) and male-induced effects (possibly under sexually antagonistic selection) cannot be disentangled. We partitioned these fundamentally different effects by instead examining the expression profiles of virgin, single mated and double mated females. We found substantial effects relating to reproduction and further effects that are only attributable to mating itself. Immune response genes dominate this male-induced effect indicating that the cost of mating may be due partly to this system's activation. We propose that both sexually antagonistic and natural selection have been important in the evolution of the innate immunity genes, thereby contributing to the sexual dimorphism and rapid evolution at these loci.

Interplay of JH, 20E and biogenic amines under normal and stress conditions and its effect on reproduction

Juvenile hormone (JH) and 20-hydroxyecdysone (20E) are well known to play a gonadotropic role in adult insects. In Drosophila the mechanism of reciprocal regulation of JH and 20E is shown to be responsible for their proper balance. Dopamine is a mediator in this JH and 20E interplay. A proper balance between JH and 20E is crucial for the normal progress of oogenesis. An imbalance of gonadotropins leads to reproductive defects: a rise in JH titre leads to oviposition arrest, a rise in 20E level, to the degradation of vitellogenic oocytes. Upon a change in the level of one of the gonadotropins, the balance is restored owing to the relative change in the titre of the other.

Role of arylalkylamine N-acetyltransferase in regulation of biogenic amines levels by gonadotropins in Drosophila

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the arylalkylamine N-acetyltransferase (AANAT) was studied in young females of wild-type D. virilis and D. melanogaster. 20E feeding of the flies led to a decrease in AANAT activity in both species when dopamine (DA) was used as substrate, but did not affect the enzyme activity when octopamine (OA) was used as substrate. JH application increased AANAT activity with DA as substrate in both species, but did not change it with OA as substrate. AANAT activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous ( 56f ). A decrease in the enzyme activity was observed in the mutant females as compared to wild-type. Mechanisms of regulation of DA level by gonadotropins in Drosophila are discussed.

Role of ecdysone 20-monooxygenase in regulation of 20-hydroxyecdysone levels by juvenile hormone and biogenic amines in Drosophila

The effects of increased levels of dopamine (feeding flies with dopamine precursor, L: -dihydroxyphenylalanine) and octopamine (feeding flies with octopamine) on ecdysone 20-monooxygenase activity in young (2 days old) wild type females (the strain wt) of Drosophila virilis have been studied. L: -dihydroxyphenylalanine and octopamine feeding increases ecdysone 20-monooxygenase activity by a factor of 1.6 and 1.7, respectively. Ecdysone 20-monooxygenase activity in the young (1 day old) octopamineless females of the strain Tbetah ( nM18 ), in females of the strain P845 (precursor of Tbetah ( nM18 ) strain) and in wild type females (Canton S) of Drosophila melanogaster have been measured. The absence of octopamine leads to a considerable decrease in the enzyme activity. We have also studied the effects of juvenile hormone application on ecdysone 20-monooxygenase activity in 2-day-old wt females of D. virilis and demonstrated that an increase in juvenile hormone titre leads to an increase in the enzyme activity. We discuss the supposition that ecdysone 20-monooxygenase occupies a key position in the regulation of 20-hydroxyecdysone titre under the conditions that lead to changes in juvenile hormone titre and biogenic amine levels.

Dopamine and octopamine regulate 20-hydroxyecdysone level in vivo in Drosophila

The effects of increased level of dopamine (DA) (feeding flies with DA precursor, L-dihydroxyphenylalanine, L-DOPA) on the level of 20-hydroxyecdysone (20E) and on juvenile hormone (JH) metabolism in young (2-day-old) wild type females (the strain wt) of Drosophila virilis have been studied. Feeding the flies with L-DOPA increased DA content by a factor of 2.5, and led to a considerable increase in 20E level and a decrease of JH degradation (an increase in JH level). We have also measured the levels of 20E in the young (1-day-old) octopamineless females of the strain Tbetah(nM18) and in wild type females, Canton S, of D. melanogaster. The absence of OA led to a considerable decrease in 20E level (earlier it was shown that in the Tbetah(nM18) females, JH degradation was sharply increased). We have studied the effects of JH application on 20E level in 2-day-old wt females of D. virilis and demonstrated that an increase in JH titre results in a steep increase of 20E level. The supposition that biogenic amines act as intermediary between JH and 20E in the control of Drosophila reproduction is discussed.

Effects of octopamine on reproduction, juvenile hormone metabolism, dopamine, and 20-hydroxyecdysone contents in Drosophila

The effect of an experimentally increased octopamine content (feeding flies with OA) on the levels of juvenile hormone (JH) degradation, dopamine (DA), and 20-hydroxyecdysone (20E) contents, oogenesis, and fecundity of wild type Drosophila flies has been studied. OA feeding of the flies was found to (1) cause a considerable decrease in JH degradation in females, but not males, of D. melanogaster and D. virilis; (2) have no effect on DA content in D. melanogaster and D. virilis; (3) increase 20E contents in D. virilis females; (4) decrease to a large extent the number of vitellogenic (stages 8-10) and mature (stage 14) oocytes in D. virilis; and (5) decrease the fecundity of D. melanogaster and D. virilis. A possible mechanism of action of OA as a neurohormone on the reproductive function of Drosophila is discussed.

Effects of juvenile hormone and 20-hydroxyecdysone on alkaline phosphatase activity in Drosophila under normal and heat stress conditions

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the alkaline phosphatase (ALP) has been studied in young females of wild-type Drosophila virilis and Drosophila melanogaster under normal conditions and under heat stress (38 degrees C). Both 20E feeding of the flies and JH application led to a substantial rise in ALP activity. ALP activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous(56f). A decrease in the enzyme activity was observed in the mutant females as compared to wild type. A rise in JH and 20E levels was found not to prevent the response of ALP to heat stress, but to change its stress-reactivity. Mechanisms of regulation of dopamine (DA) level by gonadotropins in Drosophila are discussed.