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David L Denlinger - One of the best experts on this subject based on the ideXlab platform.
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changes in histone acetylation as potential mediators of pupal Diapause in the flesh fly sarcophaga bullata
Insect Biochemistry and Molecular Biology, 2016Co-Authors: Julie A Reynolds, Robin Bautistajimenez, David L DenlingerAbstract:The growing appreciation that epigenetic processes are integral to the responses of many organisms to changes in the environment suggests a possible role for epigenetics in coordination of insect Diapause. The results we present suggest that histone modification may be one type of epigenetic process that contributes to regulation of pupal Diapause in the flesh fly, Sarcophaga bullata. Reduction in total histone H3 acetylation in diapausing pupae, shifts in mRNA expression profiles of genes encoding histone acetyltransferase (HAT) and histone deacetylase (HDAC) in pre-Diapause, Diapause and post-Diapause flies compared to their nonDiapause counterparts, and alterations in HDAC enzyme activity during and post-Diapause lend support to the hypothesis that this specific type of histone modification is involved in regulating Diapause programming, maintenance, and termination. Transcription of genes encoding HDAC1, HDAC3, HDAC6, and Sirtuin2 were all upregulated in photosensitive first instar larvae programmed to enter pupal Diapause, suggesting that histone deacetylation may be linked to the early decision to enter Diapause. A 50% reduction in transcription of hdac3 and a corresponding 30% reduction in HDAC activity during Diapause suggest that removal of acetyl groups from histones primarily occurs prior to Diapause entry and that further histone deacetylation is not necessary to maintain Diapause. Transcription of the HDAC genes was quickly elevated when Diapause was terminated, followed by an increase in enzyme activity after a short delay. A maternal effect operating in these flies prevents pupal Diapause in progeny whose mothers experienced pupal Diapause, even if the progeny are reared in strong Diapause-inducing short-day conditions. Such nondiapausing pupae had HDAC transcription profiles nearly identical to the profiles seen in nondiapausing pupae generated under a long-day photoperiod. Together, these results provide consistent evidence for histone acetylation and deacetylation as regulators of this insect's developmental trajectory.
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Molecular Physiology of Mosquito Diapause
Advances in Insect Physiology, 2016Co-Authors: David L Denlinger, P.a. ArmbrusterAbstract:Abstract The dormant state of Diapause is exploited by numerous mosquito species to survive seasonal periods of environmental stress. We discuss embryonic, larval and adult Diapauses in mosquitoes and probe the molecular and physiological distinctions that comprise the Diapause phenotype. Diapause evokes diverse and unique attributes including behavioural changes, arrested development, enhanced stress tolerance, fat accumulation and suppressed metabolic rates. Like most insects, mosquitoes in temperate latitudes precisely monitor daylength as a cue for Diapause initiation. We examine the role of circadian clock genes in this response and trace downstream hormonal pathways involved in the Diapause response. Insulin and the FOXO transcription factor signalling pathways appear to be keys for generating the Diapause phenotype in adult females of Culex pipiens and perhaps other species. Elucidating the molecular regulation of Diapause-associated physiology may provide a basis to identify novel targets for the control of mosquito vectors.
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functional circadian clock genes are essential for the overwintering Diapause of the northern house mosquito culex pipiens
The Journal of Experimental Biology, 2015Co-Authors: Megan E Meuti, Mary Stone, Tomoko Ikeno, David L DenlingerAbstract:The short day lengths of late summer are used to program the overwintering adult Diapause (dormancy) of the Northern house mosquito, Culex pipiens. Here, we investigated the role of clock genes in initiating this Diapause and asked whether the circadian cycling of clock gene expression persists during Diapause. We provide evidence that the major circadian clock genes continue to cycle throughout Diapause and after Diapause has been terminated. RNA interference (RNAi) was used to knock down the core circadian clock genes and to then assess the impact of the various clock genes on the ability of females to enter Diapause. RNAi directed against negative circadian regulators (period, timeless and cryptochrome2) caused females that were reared under Diapause-inducing, short day conditions to avert Diapause. In contrast, knocking down the circadian-associated gene pigment dispersing factor caused females that were reared under Diapause-averting, long day conditions to enter a Diapause-like state. Our results implicate the circadian clock in the initiation of Diapause in C. pipiens.
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Imidazole derivative KK-42 boosts pupal Diapause incidence and delays Diapause termination in several insect species
Journal of Insect Physiology, 2015Co-Authors: Yanqun Liu, Qirui Zhang, David L DenlingerAbstract:The imidazole derivative KK-42 is a synthetic insect growth regulator known previously to be capable of averting embryonic Diapause in several Lepidoptera, but whether it also affects Diapauses occurring in other developmental stages remains unknown. In the present study, we examined the effect of KK-42 on pupal Diapause in two species of Lepidoptera, the Chinese oak silkworm Antheraea pernyi and the corn earworm Helicoverpa zea, and in one species of Diptera, the flesh fly Sarcophaga crassipalpis. In A. pernyi, KK-42 delayed pupal Diapause termination under the long day conditions that normally break Diapause in this species. Likewise, in H. zea, KK-42 delayed termination of pupal Diapause, a Diapause that, in this species, is normally broken by high temperature. KK-42-treated pupae of these two species eventually terminated Diapause and successfully emerged as adults, but the timing of Diapause termination was significantly delayed. KK-42 also significantly increased the incidence of pupal Diapause in H. zea and S. crassipalpis when administered to larvae that were environmentally programmed for Diapause, but it was not capable of inducing pupal Diapause in H. zea if larvae were reared under environmental conditions that do not normally evoke the Diapause response. Experiments with H. zea showed that the effect of KK-42 on pupal Diapause was dose- and stage-dependent, but not temperature-dependent. Results presented here are consistent with a link between KK-42 and the ecdysteroid signaling pathway that regulates pupal Diapause.
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transcriptional evidence for small rna regulation of pupal Diapause in the flesh fly sarcophaga bullata
Insect Biochemistry and Molecular Biology, 2013Co-Authors: Julie A Reynolds, Jennifer Clark, Stephen J Diakoff, David L DenlingerAbstract:Abstract Understanding the molecular basis of Diapause, a phenotypically plastic, alternative developmental pathway, is key to predicting the seasonal distribution of economically and medically important insect species. Small regulatory RNAs, including piwi-related RNAs, small-interfering RNAs, and miRNAs, represent one type of epigenetic process that can alter the phenotype of organisms independent of changes in genome sequence. We hypothesize that small RNAs regulate pupal Diapause and a maternal block of Diapause in the flesh fly Sarcophaga bullata . We assessed the relative abundance of eight genes related to small RNA biogenesis and function using qRT-PCR in pre-Diapause and Diapause stages compared to their non-Diapause counterparts. Elevated mRNA expression of piwi and spindle-E , as well as argonaute2 and r2d2 , in photosensitive 1st instar larvae reared in Diapause-inducing conditions indicate involvement of the piwi-associated RNA and small-interfering RNA pathways, respectively, in programming the switch from direct development to a developmental pathway that includes Diapause. Two genes, related to the microRNA pathway, argonaute1 and loquacious , are upregulated during pupal Diapause, suggesting a role for this pathway in maintaining Diapause. Substantial reduction in transcript abundance of small RNA-related genes in photosensitive 1st instar larvae from mothers with a Diapause history compared to those from mothers with no Diapause history also suggest a role for small RNA pathways in regulating a Diapause maternal effect in S. bullata . Together, the results point to a role for small RNAs in regulating the developmental trajectory in this species.
Lei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Diapause termination post Diapause development and reproduction in the beet webworm loxostege sticticalis lepidoptera pyralidae
Journal of Insect Physiology, 2010Co-Authors: Xing Fu Jiang, Shao Hong Huang, Lei ZhangAbstract:Abstract Effects of photoperiod and cold exposure on Diapause termination, post-Diapause development and reproduction in Loxostege sticticalis were examined. Larvae were reared at Diapause inducing condition (22 °C, L:D 12:12) consistently or transferred to long day photoperiod (L:D 16:8) and darkness (L:D 0:24) respectively, after entering into Diapause. Diapause was terminated in approximately 40% of the larvae after 36 days, and no significant differences were observed between photoperiods, suggesting larval Diapause was terminated spontaneously without being induced by photoperiods. Cold exposure significantly hastened Diapause termination. The Diapause termination incidence increased significantly with peaks of 98% at both 5 °C and 0 °C exposure for 30 days, as compared to 42% in controls not exposed to cold, while the mortality and number of days required for Diapause termination decreased dramatically. The optimal low temperature exposure periods under 5 °C or 0 °C were 20 days and 30 days, showing a higher termination incidence and shorter time for Diapause termination. This suggests that the low temperatures in winter play an important role in Diapause termination under natural conditions. The threshold temperatures for post-Diapause development in prepupae and pupae were 9.13 °C and 10.60 °C respectively, with corresponding accumulations of 125 and 200 degree-days. Adults that experienced larval Diapause significantly delayed their first oviposition, oviposition period was prolonged, and the lifetime number of eggs laid was decreased, however both males and females have significantly longer longevity. The field validation of Diapause termination, the degree-days model, and the relationship between Diapause and migration in L. sticticalis were also discussed.
Xing Fu Jiang - One of the best experts on this subject based on the ideXlab platform.
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juvenile hormone changes associated with Diapause induction maintenance and termination in the beet webworm loxostege sticticalis lepidoptera pyralidae
Archives of Insect Biochemistry and Physiology, 2011Co-Authors: Xing Fu Jiang, Shao Hong HuangAbstract:At 22°C and under a long-day photoperiod of L:D 16:8, all the last fifth instar Loxostege sticticalis larvae undergo prepupal stage and pupate without Diapause. Under a short-day photoperiod of L:D 12:12, in contrast, they all enter Diapause with approximately 36 days Diapause maintenance and then terminate Diapause spontaneously, although only 44% of the larvae terminated Diapause successfully. Changes in hemolymph juvenile hormone (JH I) titers of Diapause-destined larvae across Diapause induction, maintenance and termination were examined using HPLC, and were compared with those of non-Diapause-destined larvae from the fifth instar through pupation. JH I titer of the earliest fifth instar Diapause-destined larvae remained at a high level with a peak of 220.4 ng/ml, though it decreased continuously to a minimum of 69.0 ng/ml on day 5 in the fifth instar when the larvae stopped feeding to enter Diapause. During the Diapause maintenance, JH I titer of the mature larvae increased significantly and maintained a high level until day 31 in prepupae. JH I titer declined and fluctuated at low level from 5 days before pupation. In contrast, JH I titer of both the fifth instar non-Diapause-destined larvae and prepupae remained and fluctuated at low level consistently, as well as decreased before pupation. These results indicate that Diapause induction and maintenance in this species might be a consequence of high JH, whereas Diapause termination can be attributed to low JH titer, which was in agreement with the hormonal regulation observed in many other larval-diapausing insects. © 2011 Wiley Periodicals, Inc.
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Diapause termination post Diapause development and reproduction in the beet webworm loxostege sticticalis lepidoptera pyralidae
Journal of Insect Physiology, 2010Co-Authors: Xing Fu Jiang, Shao Hong Huang, Lei ZhangAbstract:Abstract Effects of photoperiod and cold exposure on Diapause termination, post-Diapause development and reproduction in Loxostege sticticalis were examined. Larvae were reared at Diapause inducing condition (22 °C, L:D 12:12) consistently or transferred to long day photoperiod (L:D 16:8) and darkness (L:D 0:24) respectively, after entering into Diapause. Diapause was terminated in approximately 40% of the larvae after 36 days, and no significant differences were observed between photoperiods, suggesting larval Diapause was terminated spontaneously without being induced by photoperiods. Cold exposure significantly hastened Diapause termination. The Diapause termination incidence increased significantly with peaks of 98% at both 5 °C and 0 °C exposure for 30 days, as compared to 42% in controls not exposed to cold, while the mortality and number of days required for Diapause termination decreased dramatically. The optimal low temperature exposure periods under 5 °C or 0 °C were 20 days and 30 days, showing a higher termination incidence and shorter time for Diapause termination. This suggests that the low temperatures in winter play an important role in Diapause termination under natural conditions. The threshold temperatures for post-Diapause development in prepupae and pupae were 9.13 °C and 10.60 °C respectively, with corresponding accumulations of 125 and 200 degree-days. Adults that experienced larval Diapause significantly delayed their first oviposition, oviposition period was prolonged, and the lifetime number of eggs laid was decreased, however both males and females have significantly longer longevity. The field validation of Diapause termination, the degree-days model, and the relationship between Diapause and migration in L. sticticalis were also discussed.
Shao Hong Huang - One of the best experts on this subject based on the ideXlab platform.
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juvenile hormone changes associated with Diapause induction maintenance and termination in the beet webworm loxostege sticticalis lepidoptera pyralidae
Archives of Insect Biochemistry and Physiology, 2011Co-Authors: Xing Fu Jiang, Shao Hong HuangAbstract:At 22°C and under a long-day photoperiod of L:D 16:8, all the last fifth instar Loxostege sticticalis larvae undergo prepupal stage and pupate without Diapause. Under a short-day photoperiod of L:D 12:12, in contrast, they all enter Diapause with approximately 36 days Diapause maintenance and then terminate Diapause spontaneously, although only 44% of the larvae terminated Diapause successfully. Changes in hemolymph juvenile hormone (JH I) titers of Diapause-destined larvae across Diapause induction, maintenance and termination were examined using HPLC, and were compared with those of non-Diapause-destined larvae from the fifth instar through pupation. JH I titer of the earliest fifth instar Diapause-destined larvae remained at a high level with a peak of 220.4 ng/ml, though it decreased continuously to a minimum of 69.0 ng/ml on day 5 in the fifth instar when the larvae stopped feeding to enter Diapause. During the Diapause maintenance, JH I titer of the mature larvae increased significantly and maintained a high level until day 31 in prepupae. JH I titer declined and fluctuated at low level from 5 days before pupation. In contrast, JH I titer of both the fifth instar non-Diapause-destined larvae and prepupae remained and fluctuated at low level consistently, as well as decreased before pupation. These results indicate that Diapause induction and maintenance in this species might be a consequence of high JH, whereas Diapause termination can be attributed to low JH titer, which was in agreement with the hormonal regulation observed in many other larval-diapausing insects. © 2011 Wiley Periodicals, Inc.
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Diapause termination post Diapause development and reproduction in the beet webworm loxostege sticticalis lepidoptera pyralidae
Journal of Insect Physiology, 2010Co-Authors: Xing Fu Jiang, Shao Hong Huang, Lei ZhangAbstract:Abstract Effects of photoperiod and cold exposure on Diapause termination, post-Diapause development and reproduction in Loxostege sticticalis were examined. Larvae were reared at Diapause inducing condition (22 °C, L:D 12:12) consistently or transferred to long day photoperiod (L:D 16:8) and darkness (L:D 0:24) respectively, after entering into Diapause. Diapause was terminated in approximately 40% of the larvae after 36 days, and no significant differences were observed between photoperiods, suggesting larval Diapause was terminated spontaneously without being induced by photoperiods. Cold exposure significantly hastened Diapause termination. The Diapause termination incidence increased significantly with peaks of 98% at both 5 °C and 0 °C exposure for 30 days, as compared to 42% in controls not exposed to cold, while the mortality and number of days required for Diapause termination decreased dramatically. The optimal low temperature exposure periods under 5 °C or 0 °C were 20 days and 30 days, showing a higher termination incidence and shorter time for Diapause termination. This suggests that the low temperatures in winter play an important role in Diapause termination under natural conditions. The threshold temperatures for post-Diapause development in prepupae and pupae were 9.13 °C and 10.60 °C respectively, with corresponding accumulations of 125 and 200 degree-days. Adults that experienced larval Diapause significantly delayed their first oviposition, oviposition period was prolonged, and the lifetime number of eggs laid was decreased, however both males and females have significantly longer longevity. The field validation of Diapause termination, the degree-days model, and the relationship between Diapause and migration in L. sticticalis were also discussed.
Julie A Reynolds - One of the best experts on this subject based on the ideXlab platform.
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changes in histone acetylation as potential mediators of pupal Diapause in the flesh fly sarcophaga bullata
Insect Biochemistry and Molecular Biology, 2016Co-Authors: Julie A Reynolds, Robin Bautistajimenez, David L DenlingerAbstract:The growing appreciation that epigenetic processes are integral to the responses of many organisms to changes in the environment suggests a possible role for epigenetics in coordination of insect Diapause. The results we present suggest that histone modification may be one type of epigenetic process that contributes to regulation of pupal Diapause in the flesh fly, Sarcophaga bullata. Reduction in total histone H3 acetylation in diapausing pupae, shifts in mRNA expression profiles of genes encoding histone acetyltransferase (HAT) and histone deacetylase (HDAC) in pre-Diapause, Diapause and post-Diapause flies compared to their nonDiapause counterparts, and alterations in HDAC enzyme activity during and post-Diapause lend support to the hypothesis that this specific type of histone modification is involved in regulating Diapause programming, maintenance, and termination. Transcription of genes encoding HDAC1, HDAC3, HDAC6, and Sirtuin2 were all upregulated in photosensitive first instar larvae programmed to enter pupal Diapause, suggesting that histone deacetylation may be linked to the early decision to enter Diapause. A 50% reduction in transcription of hdac3 and a corresponding 30% reduction in HDAC activity during Diapause suggest that removal of acetyl groups from histones primarily occurs prior to Diapause entry and that further histone deacetylation is not necessary to maintain Diapause. Transcription of the HDAC genes was quickly elevated when Diapause was terminated, followed by an increase in enzyme activity after a short delay. A maternal effect operating in these flies prevents pupal Diapause in progeny whose mothers experienced pupal Diapause, even if the progeny are reared in strong Diapause-inducing short-day conditions. Such nondiapausing pupae had HDAC transcription profiles nearly identical to the profiles seen in nondiapausing pupae generated under a long-day photoperiod. Together, these results provide consistent evidence for histone acetylation and deacetylation as regulators of this insect's developmental trajectory.
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transcriptional evidence for small rna regulation of pupal Diapause in the flesh fly sarcophaga bullata
Insect Biochemistry and Molecular Biology, 2013Co-Authors: Julie A Reynolds, Jennifer Clark, Stephen J Diakoff, David L DenlingerAbstract:Abstract Understanding the molecular basis of Diapause, a phenotypically plastic, alternative developmental pathway, is key to predicting the seasonal distribution of economically and medically important insect species. Small regulatory RNAs, including piwi-related RNAs, small-interfering RNAs, and miRNAs, represent one type of epigenetic process that can alter the phenotype of organisms independent of changes in genome sequence. We hypothesize that small RNAs regulate pupal Diapause and a maternal block of Diapause in the flesh fly Sarcophaga bullata . We assessed the relative abundance of eight genes related to small RNA biogenesis and function using qRT-PCR in pre-Diapause and Diapause stages compared to their non-Diapause counterparts. Elevated mRNA expression of piwi and spindle-E , as well as argonaute2 and r2d2 , in photosensitive 1st instar larvae reared in Diapause-inducing conditions indicate involvement of the piwi-associated RNA and small-interfering RNA pathways, respectively, in programming the switch from direct development to a developmental pathway that includes Diapause. Two genes, related to the microRNA pathway, argonaute1 and loquacious , are upregulated during pupal Diapause, suggesting a role for this pathway in maintaining Diapause. Substantial reduction in transcript abundance of small RNA-related genes in photosensitive 1st instar larvae from mothers with a Diapause history compared to those from mothers with no Diapause history also suggest a role for small RNA pathways in regulating a Diapause maternal effect in S. bullata . Together, the results point to a role for small RNAs in regulating the developmental trajectory in this species.