Juvenile Hormone Analog Research Articles

Validation of reference gene(s) for quantitative gene expression profiling using rice moth, Corcyra cephalonica as a model

Many techniques are available for the quantification of specific mRNA from various tissues of an organism. Among them qRT-PCR is a widely used method, as this is a rapid and requires low quantity of mRNA. The reliability of the data depends on accurate normalization using appropriate internal control(s). The use of constitutively expressed genes (house-keeping genes, HKGs) such as α-actin, β-tubulin and GAPDH as internal controls or reference genes is a widely accepted method for qRT-PCR data normalization. However, expression of HKGs may vary at different developmental stages or during hormone manipulation studies. The present study was carried out using a holometabolous lepidopteran stored grain pest Corcyra cephalonica (rice moth). Seven different constitutively expressed genes α-actin, β-tubulin, 18S rRNA, TBP, rS7, GAPDH, and EF1α were analysed as internal reference genes in various larval tissues. Further the stable gene was characterized during various conditions like ontogeny, hormonal depletion and exogenous hormone application. Gene expression stability was obtained by measuring the M-value for HKGs. The findings indicate that 18S rRNA was suitable as reference gene under normal physiological conditions, tissue distribution and also upon methoprene (JH analog) treatment. On the other hand rS7 was suitable for ecdysteroid treatment related analysis. Present study once again reinforces that, reference genes cannot be universal and need to be validated not only for a given organism but also during various conditions.

Insect Juvenoids: Structural Qualifications and Structure-Activity Relationships of Alkylphenoxy-Substituted Terpenes as Insect Growth Disruptors AgainstSpodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) – Revisited

Insect growth disruptors of the aryl terpenoid ether type including 185 compounds derived from 10 basic olefinic, epoxidised and alkoxidised type-structures were tested against the prepupae of the Mediterranean brocade, Spodoptera littoralis. The potent decenyl compounds are mainly derivatives of 4,8-dimethyl-3,7-decadiene and the epoxides of its external olefinic bond. The potent nonenyl compounds are mainly derivatives of either 4,8-dimethyl-3,7-nonadiene and the epoxides of its external olefinic bond or 3,7-dimethyl 6,7-epoxy-2-nonene. The phenyl group of the potent compounds have either methylenedioxy (3,4-), ethyl or methyl groups (4- or 3-). The presence of an alkoxy group on the terpenoid side chain, and/or the phenyl group does not lead to formation of a potent compound. The addition of one terminal carbon atom to some nonenyl derivatives leads to activity in the resulting decenyl compound. Continuing studies on synthetic juvenile hormone analogues may provide novel potent compounds for more benign insect control strategies.

Effects of larval diapause and the juvenile hormone analog, fenoxycarb, on testis development and spermatogenesis in the wax moth, Galleria mellonella (Lepidoptera: Pyralidae)

Facultative diapause in the wax moth, Galleria mellonella, occurs in the final larval instar. Application of juvenile hormone analogs (JHAs) to the larvae of this species has similar effects to diapause, in terms of prolonged development of the larval stages and the arrest in the metamorphosis of internal organs. Here, we focus on testes development and spermatogenesis at the end of larval development in G. mellonella, how they are affected by diapause induced by an environmental decrease in temperature to 18°C and the application of a JHA (fenoxycarb) to larvae. Because neither testis development nor spermatogenesis are described in detail for this species, we examined them in individuals not in diapause during the period from the last larval instar to the newly emerged adult and present a timetable of changes that occur in the development of testes in this species. These observations have increased the very limited data on the course of spermatogenesis in pyralid insects. We then used these data for comparative analysis of testes in larvae from two experimental groups: individuals in diapause and those treated with fenoxycarb. The results on the general morphology testes revealed obvious degenerative changes caused by fenoxycarb (but not by diapause), including testicular wall hypertrophy and disarrangement of testicular follicles. Moreover, treatment with fenoxycarb finally resulted in the disintegration of nearly all testicular cyst-containing germ cells at different stages of spermatogenesis, a situation never previously described in the literature. In contrast, the main effect of diapause on testes was merely the degeneration of spermatocytes in the proximal regions of the testicular follicles. Finally, the TUNEL analyses, revealed that the degenerative changes in germ cells were apoptotic in character in the testes of both individuals in diapause and fenoxycarb-treated males.

A non-venomous sPLA2 of a lepidopteran insect: Its physiological functions in development and immunity

Eicosanoids are oxygenated C20 polyunsaturated fatty acids that mediate various physiological processes in insects. Eicosanoid biosynthesis begins with a C20 precursor, arachidonic acid (5,8,11,14-eicosatetraenoic acid: AA). AA is usually released from phospholipids at sn-2 position by catalytic activity of phospholipase A2 (PLA2). Although various PLA2s classified into 16 gene families (= Groups) are known in various biological systems, few PLA2s are known in insects. Only two PLA2s involved in intracellular calcium independent PLA2 (iPLA2) group have been identified in lepidopteran insects with well known eicosanoid physiology. This study reports the first secretory PLA2 (sPLA2) in lepidopteran insects. A partial open reading frame (ORF) of PLA2 was obtained by interrogating Spodoptera exigua transcriptome. Subsequent 3′-RACE resulted in a full ORF (Se-sPLA2A) encoding 194 amino acid sequence containing signal peptide, calcium-binding domain, and catalytic site. Phylogenetic analysis indicated that Se-sPLA2A was clustered with other Group III sPLA2s. Se-sPLA2A was expressed in most larval instars except late last instar. Its expression was inducible by immune challenge and juvenile hormone analog injection. RNA interference of Se-sPLA2A significantly suppressed cellular immunity and impaired larval development. These results suggest that non-venomous sPLA2 plays a crucial role in immune and developmental processes in S. exigua, a lepidopteran insect.

Evaluation of bio-efficacy and residual activity of pyriproxyfen against field collected aedes aegypti and aedes albopictus from Gujranwala (Punjab), Pakistan

Background: Abstract Background: Dengue disease is a major health problem in tropical and subtropical region of the world. Pakistan has also serious issues on this infectious disease in the form of DF, DHF & DSS since 1994 when it was declared the first epidemic in Pakistan. Since then, many epidemics in different cities of Pakistan have been occurring on regular basis. The ever worst epidemic was occurred in 2011 in Punjab province where more than 286857 suspected cases and 21685 confirmed cases with 350 deaths were reported by Health Department. There is an urgent need for entomological and epidemiological studies on large scale to control the disease. Methods & Materials: Methodology: The recent study was conducted in district Gujranwala-Punjab, Pakistan to evaluate the Bio-efficacy of pyriproxyfen (a juvenile hormone analogue) against field collected mosquitoes (larvae) of dengue vectors. Aedes aegypti and Aedes albopictus were collected from three different localities of Aroop Town. Collected mosquitoes were reared to get fresh larvae according to the WHO recommended rearing procedure. Larvae were treated with pyriproxyfen (Predator 0.5 WDG) at the WHO recommended dose of 0.01 mg/l of a.i. The tests were conducted in triplicate form along with a control. A fresh lot of 25 larvae were added in all treated as well as in control cups on every ten days interval to determine the residual activity of the tested product. Results: Result: The bio-efficacy of pyriproxyfen was found effective against field collected Aedes aegypti and Aedes albopictus. The complete Inhibition of Adult Emergence (EI) was observed 58 days and 47 days for Aedes aegypti and Aedes albopictus respectively. The results also show that the residual activity of pyriproxyfen against Aedes aegypti is greater than Aedes albopictus as 68 days and 59 days (up to 80% EI) respectively. Conclusion: Conclusions: Pyriproxyfen can be used to control the dengue vectors (Aedes aegypti and Aedes albopictus) and it can be included in integrated vector control strategy. It is very effective and safer to use for vector control as non-conventional usage of chemical insecticides.

A plant diterpene counteracts juvenile hormone-mediated gene regulation during Drosophila melanogaster larval development

Many plant species possess compounds with juvenile hormone disruptor (JHD) activity. In some plant species, such activity has been attributed to diterpene secondary metabolites. Plant JHD diterpenes disrupt insect development by interfering with the juvenile hormone (JH)-mediated formation of JH receptor complexes. Here, we demonstrate that a plant extract and a diterpene from Lindera erythrocarpa (methyl lucidone) interfere with the formation of both methoprene-tolerant (Met)/Taiman and Germ cell-expressed (GCE)/Taiman heterodimer complexes in yeast two-hybrid assays in vitro. In addition to the in vitro JHD activity, the diterpene and the plant extract from L. erythrocarpa also disrupt the development of larvae and pupae in Drosophila melanogaster. Comparing the transcriptomes of juvenile hormone analog (JHA, methoprene)- and JHD (methyl lucidone)-fed wandering third-instar larvae revealed a large number of genes that were coregulated by JHA and JHD. Moreover, most (83%) of the genes that were repressed by methyl lucidone were significantly activated by methoprene, indicating that JHDs and JHAs have opposing effects on the transcriptional regulation of many JH-dependent genes. Gene ontology analysis also suggested that some of the genes activated-by-JHA/repressed-by-JHD play roles in spermatogenesis. Affymetrix microarray-based analysis indicated that the expression of genes activated-by-JHA/repressed-by-JHD was testis-specific. Together, these results suggest that JH is involved in testis-specific gene expression and that plant JHD diterpenes function as JH antagonists in such JHA-mediated gene regulation.

Dietary methoprene supplement promotes early sexual maturation of male Queensland fruit fly Bactrocera tryoni

Sterile insect technique (SIT) is an environmentally benign pest management technique that relies on released sterile male insects mating with, and curtailing reproduction of, wild females. However, for species with high mortality rates and long adult maturation phases, a large proportion of the released insects can die before maturing and so fail to contribute to SIT. To counter this problem, inclusion of yeast hydrolysate in pre-release diets and treatment of pupae or adults with methoprene, a juvenile hormone analogue, have been investigated as means of accelerating development of some fruit flies, including Queensland fruit fly, Bactrocera tryoni (Froggatt) (‘Q-fly’). Methoprene has most often been administered topically in acetone solution, which is toxic, flammable, and impractical for operational settings. As a practical alternative, we incorporated methoprene (0, 0.05, 0.1, and 0.5%) into Q-fly adult diet of sugar only or sugar mixed with yeast hydrolysate for 2 days, and then provided sugar only for the rest of the trial period. Mating performance of males and females was tested from 4 to 30 days of age. Flies provided sugar mixed with yeast hydrolysate had increased mating propensity in comparison with flies that were provided sugar only. At all ages and for both diets, all methoprene doses increased male mating probability. Methoprene treatment did not affect copula latency of males that received yeast hydrolysate, but males that received only sugar mated earlier if they had received 0.05% methoprene. Methoprene treatment of males was also associated with longer copulations, which may affect fertility of females that later remate. Females differed from males in that methoprene treatment did not significantly affect mating probability or latency, but resembled males in that methoprene treatment resulted in longer copulations. Sex differences in response to methoprene may lead to male-biased operational sex ratio when bisex Q-fly strains are used in SIT. Yeast hydrolysate increased longevity of both males and females, but methoprene treatment did not affect longevity. Overall, findings of the present study indicate that Q-fly sexual maturation can be accelerated, and SIT might hence be enhanced, by incorporation of methoprene and yeast hydrolysate in pre-release diet.

Digging Deeper Into the Pyriproxyfen-Response of the Amphipod Gammarus fossarum With a Next-Generation Ultra-High-Field Orbitrap Analyser: New Perspectives for Environmental Toxicoproteomics

Taxon-specific proteins from sentinel species have been shown to be among the most relevant proteins to monitor the biological effects of anthropogenic contaminations. Shotgun proteomics allows high-throughput analysis of animal proteomes, but comprehensive coverage remains difficult to achieve due to the wide dynamic range. Here, the advantages of a new generation of mass analyser for environmental toxicoproteomics are documented through the identification of candidate biomarkers in a sentinel animal species for which the genome is as yet unsequenced. A label-free comparative proteomic study was performed on testis from the freshwater amphipod Gammarus fossarum challenged with 0.5 µg or 50 µg/L pyriproxyfen, a juvenile hormone analogue used as an insecticide. A total of 4,031 proteins could be monitored with a Q Exactive HF mass spectrometer incorporating an ultra-high-field Orbitrap analyser. Five times more MS/MS spectra and 4-fold more peptides and proteins were identified with this instrument compared to a LTQ Orbitrap XL spectrometer. Comparison of protein abundance between control and organisms exposed to 0.5 µg or 50 µg/L pyriproxyfen indicated that 32 and 21 proteins, respectively, were significantly modulated between test and control conditions. Functional annotation of these novel candidate biomarkers and their specificities are discussed in light of their potential applications in freshwater quality monitoring. The potential contribution of next-generation mass spectrometers to environmental toxicoproteomics is also touched on.

Expression analysis of vitellogenins in the workers of the red imported fire ant (Solenopsis invicta).

Vitellogenin has been proposed to regulate division of labor and social organization in social insects. The red imported fire ant (Solenopsis invicta) harbors four distinct, adjacent vitellogenin genes (Vg1, Vg2, Vg3, and Vg4). Contrary to honey bees that have a single Vg ortholog as well as potentially fertile nurses, and to other ant species that lay trophic eggs, S. invicta workers completely lack ovaries or the ability to lay eggs. This provides a unique model to investigate whether Vg duplication in S. invicta was followed by subfunctionalization to acquire non-reproductive functions and whether Vg was co-opted to regulate behavior within the worker caste. To investigate these questions, we compared the expression patterns of S. invicta Vg genes among workers from different morphological subcastes or performing different tasks. RT-qPCRs revealed higher relative expression of Vg1 in major workers compared to both medium and minor workers, and of Vg2 in major workers when compared to minor workers. Relative expression of Vg1 was also higher in carbohydrate foragers when compared to nurses and protein foragers. By contrast, the level of expression of Vg2, Vg3, and Vg4 were not significantly different among the workers performing the specific tasks. Additionally, we analyzed the relationship between the expression of the Vg genes and S-hydroprene, a juvenile hormone analog. No changes in Vg expression were recorded in workers 12 h after application of the analog. Our results suggest that in S. invicta the Vg gene underwent subfunctionalization after duplication to new functions based on the expression bias observed in these data. This may suggest an alternative and still unknown function for Vg in the workers that needs to be investigated further.

Involvement of Met and Kr-h1 in JH-Mediated Reproduction of Female Bactrocera dorsalis (Hendel).

Juvenile hormone (JH) prevents metamorphosis during insect larval stages and promotes adult reproductive processes. Krüppel-homolog 1 (Kr-h1), a zinc finger transcription factor assumed to be induced by JH via the JH receptor methoprene-tolerant (Met), mediates the antimetamorphic effect of JH in insects, but its function in JH-mediated reproductive processes has not been fully explored. In this study, Met and Kr-h1 involved in the JH signaling pathway were first cloned and identified from the oriental fruit fly, Bactrocera dorsalis, an important pest infesting fruit and vegetables worldwide. Subsequent spatiotemporal expression analysis revealed that Met and Kr-h1 were both highly expressed in 7-day-old adults and fat body of female adults, respectively. Treatment with a JH analog (methoprene) significantly induced the expression of JH signaling and vitellogenin (Vg) genes and accelerated ovary development. RNA interference (RNAi) further revealed that either Met or Kr-h1 depletion at the adult stage of B. dorsalis impeded ovary development, with significantly lower egg production noted as well. In addition, rescue through methoprene application after RNAi stimulated the expression of JH signaling and Vg genes. Although there were still differences in ovary phenotype between rescued insects and the pre-RNAi control, ovary redevelopment with a larger surface area was observed, consistent with the spatiotemporal expression and phenotypes recorded in the original methoprene experiment. Our data reveal the involvement of Met and Kr-h1 in insect vitellogenesis and egg production, thus indicating the crucial role of the JH signaling pathway in insect reproduction.

Dissecting the role of Krüppel homolog 1 in the metamorphosis and female reproduction of the cotton bollworm, Helicoverpa armigera.

In insects, metamorphosis and reproduction are controlled by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Krüppel homolog 1 (Kr-h1), a transcription factor, is regarded as a JH-early inducible gene responsible for the repression of metamorphosis. However, the role of Kr-h1 in reproduction of holometabolic insects is relatively less understood. In this study, we studied the role of Kr-h1 in larvae-pupae transition and female reproduction in the major agricultural pest Helicoverpa armigera. Two HaKr-h1 isoforms (HaKr-h1α and HaKr-h1ß) were identified, with HaKr-h1α predominant in the cotton bollworm. In larvae, HaKr-h1 was predominately expressed in the epidermis and markedly up-regulated during the moult stage, whereas in adults HaKr-h1 was mainly expressed in females and the highest transcription was detected in the ovaries. Considering the function of hormones in larval metamorphosis, we examined the modulation of gene expression in response to hormones, which showed that HaKr-h1 was significantly induced by both JH analogue (JHA) and 20E. Knockdown of HaKr-h1 in fifth-instar larvae resulted in precocious metamorphosis from larvae to pupae. Moreover, a fluorescence immunoassay coupled with heterologous expression revealed that HaKr-h1 was localized in the nucleus of oocyte membrane. In female adults, depletion of HaKr-h1 severely repressed the transcription of vitellogenin, disrupted oocyte maturation and reduced the number of eggs laid, suggesting that HaKr-h1 is required for vitellogenesis and egg production in H.armigera. The present study provides insight into the roles of HaKr-h1 in JH-mediated reproduction and highlights HaKr-h1 as a target for suppression of lepidopteran pests.

Acute and chronic effects of exposure to the juvenile hormone analog fenoxycarb during sexual reproduction in Daphnia magna.

Recent studies have demonstrated that insect growth regulating insecticides are able to affect reproductive endpoints in zooplankton species at very low levels. For the cyclic parthenogenetic water flea Daphnia, most of this research has focused on the asexual part of the life cycle and induction of male offspring. Even though Daphnia and many other aquatic invertebrates rely on sexual reproduction and subsequent production of dormant eggs to recover from environmentally harsh conditions, much less is known about the effects of toxicants on the sexual reproductive phase. Using fenoxycarb as a model pesticide, we exposed male and female neonate Daphnia magna, under conditions inducing a switch to sexual reproduction, and tested for effects on dormant egg (ephippia) production and sex ratio of parthenogenetic offspring. Subsequently, we assessed whether fenoxycarb exposure affected the quality of the produced dormant eggs and viability of the hatchlings. Our results showed that exposure to sub-lethal concentrations of fenoxycarb caused a sharp decrease in parthenogenetic reproduction, while inducing male offspring. Dormant egg production was marginally negatively affected, but survival and fitness of the hatched individuals were not significantly affected. This indicates that under pesticide stress, surviving adult females invested in sexual reproduction at the expense of parthenogenetic reproduction. Exposure to toxicants during the sexual reproductive phase, could affect the active aquatic phase as well as the dormant phase in natural zooplankton populations. This indicates the need for further ecotoxicological research and development of test protocols taking into account the full life cycle of zooplankton species.

TGFβ signaling related genes are involved in hormonal mediation during termite soldier differentiation.

A working knowledge of the proximate factors intrinsic to sterile caste differentiation is necessary to understand the evolution of eusocial insects. Genomic and transcriptomic analyses in social hymenopteran insects have resulted in the hypothesis that sterile castes are generated by the novel function of co-opted or recruited universal gene networks found in solitary ancestors. However, transcriptome analysis during caste differentiation has not been tested in termites, and evolutionary processes associated with acquiring the caste are still unknown. Termites possess the soldier caste, which is regarded as the first acquired permanently sterile caste in the taxon. In this study, we performed a comparative transcriptome analysis in termite heads during 3 molting processes, i.e., worker, presoldier and soldier molts, under natural conditions in an incipient colony of the damp-wood termite Zootermopsis nevadensis. Although similar expression patterns were observed during each molting process, more than 50 genes were shown to be highly expressed before the presoldier (intermediate stage of soldier) molt. We then performed RNA interference (RNAi) of the candidate 13 genes, including transcription factors and uncharacterized protein genes, during presoldier differentiation induced by juvenile hormone (JH) analog treatment. Presoldiers induced after RNAi of two genes related to TGFβ (Transforming growth factor beta) signaling were extremely unusual and possessed soldier-like phenotypes. These individuals also displayed aggressive behaviors similar to natural soldiers when confronted with Formica ants as hypothetical enemies. These presoldiers never molted into the next instar, presumably due to the decreased expression levels of the molting hormone (20-hydroxyecdysone; 20E) signaling genes. These results suggest that TGFβ signaling was acquired for the novel function of regulating between JH and 20E signaling during soldier differentiation in termites.

Estimation of population-level effect of the endocrine disruptor pyriproxyfen in Daphnia magna by using changes in sex ratio and reproductive output

Here we developed an analytical means of estimating population-level effects of endocrine disruptors on Daphnia magna. Our approach was based on the fact that the endocrine-disrupting juvenile hormone analogs induce the production of male neonates if they are exposed to the analogs during a particular period in their prenatal development; the method also assumed that the abnormal production of male neonates in the sake of production of female neonates reduces population growth. We constructed a linear toxicodynamics model to elucidate the period in which D. magna neonates are sensitive to exposure to the analog and also the probability of an individual neonate changing sex under specific exposure concentrations. The proposed model was applied to D. magna reproduction test data obtained under time-varying exposure to pyriproxyfen to derive the maximum-likelihood estimates and the posterior distributions of the model parameters. To quantitatively assess the ecological risk at the population level, we conducted a population dynamics simulation under two time-varying exposure scenarios (i.e., constant or pulsed exposure) by using an age-structured population model. When the change in sex ratio was based on the time-weighted average concentration during the period of sensitivity, change in sex ratio caused approximately equivalent population-level effects as did reproductive inhibition (i.e., reduction in the total number of neonates per female parent) regardless of the exposure scenario. In contrast, when change in sex ratio was based on maximum concentration during the sensitive period, change in sex ratio caused only half the population-level effects as did reproductive inhibition under constant exposure, whereas it caused a much larger population-level effect than did reproductive inhibition under pulsed exposure.

The Effects of Juvenile Hormone Analogue, Fenoxycarb on the Last Instar Testes of Bombyx mori

The development and metamorphosis of insects is regulated by juvenile hormone (JH) and ecdysone hormone, which are worked antagonist. Fenoxycarb is an effective juvenile hormone analogue on many insects. In this study, the effect of fenoxycarb on the last larval stage Bombyx mori testes was investigated. Male larvae on the 6th day of the last instar are divided into 2 groups. 1 ng of fenoxycarb dissolved in acetone was topically applied to larvae in the treatment group and the remaining 18 larvae were used as the control group. Control and treated groups were followed to until pupation from day when they showed cocoon spinning behavior. After dissection, several of testes were entreated routine histological processes and photographed. In treatment group, it was seen that fenoxycarb reduced spermatogonium formation by suppressing ecdysone release and caused a decrease in mature sperm. Remaining testes are used to the analysis of total carbohydrate and glycogen content. In conclusion, fenoxycarb has the reducing effect on spermatogenesis and it can cause to decrease of total carbohydrate content because of stress in insects. These histological and biochemical results may be in support of the use of fenoxycarb as an insect growth regulator (IGR) for harmful insects.

Comparison of the effects of constant and pulsed exposure with equivalent time-weighted average concentrations of the juvenile hormone analog pyriproxyfen on the reproduction of Daphnia magna

Short-term pulsed exposure tests have been increasingly used to evaluate the ecotoxicity of pollutants of which concentrations vary over time in the field. In pulsed exposure, time-weighted average (TWA) concentration is often used as an index of exposure. However, there have been few studies to demonstrate whether TWA concentration can be used to evaluate the effect of endocrine-disrupting chemicals on the daphnids. Pyriproxyfen is one of the juvenile hormone analogs that induces daphnids to produce male offspring. To evaluate whether peak or TWA concentration can explain the effects of pyriproxyfen on daphnid reproduction, we measured the number of offspring and the proportion of male offspring produced by Daphnia magna during 21-day under different exposure treatments, constant, single-pulse, and multi-pulse exposure, at an equivalent TWA concentration. Constant exposure of 50 ng/L pyriproxyfen did not affect either the fecundity or the proportion of male offspring, while a single-pulse exposure of 525 ng/L pyriproxyfen over 2 day at four different age did not reduce fecundity, but the proportion of male offspring increased age dependently. Multi-pulses exposure of 131 ng/L pyriproxyfen over two days four times (total eight days) resulted in a decrease in fecundity and the highest proportion of male offspring. Daily observation demonstrated that male offspring was only produced several days after the exposure to a certain concentration of pyriproxyfen. Therefore, neither TWA nor peak concentration accurately evaluated the effects of pulsed exposure of pyriproxyfen on the reproduction of D. magna, particularly its effect on the proportion of male offspring.

Identification and characterization of genes involving the early step of Juvenile Hormone pathway in Helicoverpa armigera

Juvenile hormones (JHs) are crucial regulators for multiple physiological processes in insects. In the current study, 10 genes in mevalonate pathway involved in JH biosynthesis were identified from Helicoverpa armigera. Tissue-specific expression analysis showed that six genes were highly expressed in the head which contained the JH biosynthetic gland (corpora allata). Temporal expression pattern showed that 10 of 12 genes were highly transcribed in the late 2nd-instar when the in vivo JH titer reached the peak, indicating a tight correlation between JH titer and the transcription of JH synthetic pathway genes. Moreover, ingestion of methoprene, a JH analogue, significantly suppressed the transcription of nine JH biosynthetic genes and caused a feedback upregulation of the JH degradation enzyme. Particularly, the Acetoacetyl CoA thiolase (HaAce) and Farnesyl diphosphate synthase gene 4 (HaFpps4) showed high transcript abundance, and their temporal expressions keep pace with JH fluctuations. Further study by RNAi showed that knockdown of HaFpps4 caused the decrease of JH titer, led to a negative effect on the transcript levels of other genes in JH pathway, and resulted in molting disturbance in larvae. Altogether, these results contribute to our understanding of JH biosynthesis in H. armigera and provide target genes for pest control based on JH-dependent regulation.

Hormonal Signaling Cascade during an Early-Adult Critical Period Required for Courtship Memory Retention in Drosophila

Formation and expression of memories are critical for context-dependent decision making. In Drosophila, acourting male rejected by a mated female subsequently courts less avidly when paired with a virgin female, a behavioral modification attributed to "courtship memory." Here we show the critical role of hormonal state for maintenance of courtship memory. Ecdysis-triggering hormone (ETH) is essential for courtship memory through regulation of juvenile hormone (JH) levels in adult males. Reduction of JH levels via silencing of ETH signaling genes impairs short-term courtship memory, a phenotype rescuable by the JH analog methoprene. JH-deficit-induced memory impairment involves rapid decay rather than failure of memory acquisition. A critical period governs memory performance during the first3 days of adulthood. Using sex-peptide-expressing "pseudo-mated" trainers, we find that robust courtship memory elicited in the absence of aversive chemical mating cues also is dependent on ETH-JH signaling. Finally, we find that JH acts through dopaminergic neurons and conclude that an ETH-JH-dopamine signaling cascade is required during a critical period for promotion of social-context-dependent memory.

Performance of reproductive system of Dichelops melacanthus (Hemiptera: Pentatomidae) subjected to buprofezin and pyriproxyfen: morphological analysis of ovarioles and testes

The use of insecticides known as insect growth regulators, which are considered more selective to natural enemies, may be an alternative to integrated pest management of stink bugs of the main crops in Brazil. The objective of this study was to evaluate histological changes in the reproductive system of Dichelops melacanthus as well as female fecundity and egg fertility after use of growth-regulating insecticides. The insecticides used were buprofezin (a chitin biosynthesis inhibitor) at a sublethal concentration (LC30 of 2.99 g L-1) and pyriproxyfen (a juvenile hormone analog) at a sublethal concentration (LC30 of 8.35 mL L-1). A completely randomized experimental design was used, with 10 repetitions and 10 insects per experimental unit. Two bioassays were performed: in the first bioassay, fecundity (eggs/female) and fertility (nymph eclosion) of the insects that survived the insecticides were evaluated; in the second bioassay, morphological alterations of the ovarioles of adult females and of the testes of adult male insects that survived the insecticides were evaluated. Buprofezin and pyriproxyfen did not affect the adult sex ratio or female fecundity. Pyriproxyfen reduced the percentage of ecloded nymphs (71.6%) compared with that of the control and buprofezin (96.4 and 90.6%, respectively) treatments and had an ovicidal effect, with direct and indirect action on embryogenesis. Morphological changes were observed in both treatments with buprofezin and pyriproxyfen. The alterations observed in female and male reproductive systems may occur by the action of buprofezin and pyriproxyfen on the morphology of both ovarioles and testes.

Performance of reproductive system of Dichelops melacanthus (Hemiptera: Pentatomidae) subjected to buprofezin and pyriproxyfen: morphological analysis of ovarioles and testes

The use of insecticides known as insect growth regulators, which are considered more selective to natural enemies, may be an alternative to integrated pest management of stink bugs of the main crops in Brazil. The objective of this study was to evaluate histological changes in the reproductive system of Dichelops melacanthus as well as female fecundity and egg fertility after use of growth-regulating insecticides. The insecticides used were buprofezin (a chitin biosynthesis inhibitor) at a sublethal concentration (LC30 of 2.99 g L-1) and pyriproxyfen (a juvenile hormone analog) at a sublethal concentration (LC30 of 8.35 mL L-1). A completely randomized experimental design was used, with 10 repetitions and 10 insects per experimental unit. Two bioassays were performed: in the first bioassay, fecundity (eggs/female) and fertility (nymph eclosion) of the insects that survived the insecticides were evaluated; in the second bioassay, morphological alterations of the ovarioles of adult females and of the testes of adult male insects that survived the insecticides were evaluated. Buprofezin and pyriproxyfen did not affect the adult sex ratio or female fecundity. Pyriproxyfen reduced the percentage of ecloded nymphs (71.6%) compared with that of the control and buprofezin (96.4 and 90.6%, respectively) treatments and had an ovicidal effect, with direct and indirect action on embryogenesis. Morphological changes were observed in both treatments with buprofezin and pyriproxyfen. The alterations observed in female and male reproductive systems may occur by the action of buprofezin and pyriproxyfen on the morphology of both ovarioles and testes.