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Global Transcriptional Dynamics of Diapause Induction in Non-Blood-Fed and Blood-Fed Aedes albopictus  [PDF]
Xin Huang?,Monica F. Poelchau?,Peter A. Armbruster
PLOS Neglected Tropical Diseases , 2015, DOI: 10.1371/journal.pntd.0003724
Abstract: Background Aedes albopictus is a vector of increasing public health concern due to its rapid global range expansion and ability to transmit Dengue virus, Chikungunya virus and a wide range of additional arboviruses. Traditional vector control strategies have been largely ineffective against Ae. albopictus and novel approaches are urgently needed. Photoperiodic diapause is a crucial ecological adaptation in a wide range of temperate insects. Therefore, targeting the molecular regulation of photoperiodic diapause or diapause-associated physiological processes could provide the basis of novel approaches to vector control. Methodology/Principal Findings We investigated the global transcriptional profiles of diapause induction in Ae. albopictus by performing paired-end RNA-Seq of biologically replicated libraries. We sequenced RNA from whole bodies of adult females reared under diapause-inducing and non-diapause-inducing photoperiods either with or without a blood meal. We constructed a comprehensive transcriptome assembly that incorporated previous assemblies and represents over 14,000 annotated dipteran gene models. Mapping of sequence reads to the transcriptome identified differential expression of 2,251 genes in response to diapause-inducing short-day photoperiods. In non-blood-fed females, potential regulatory elements of diapause induction were transcriptionally up-regulated, including two of the canonical circadian clock genes, timeless and cryptochrome 1. In blood-fed females, genes in metabolic pathways related to energy production and offspring provisioning were differentially expressed under diapause-inducing conditions, including the oxidative phosphorylation pathway and lipid metabolism genes. Conclusions/Significance This study is the first to utilize powerful RNA-Seq technologies to elucidate the transcriptional basis of diapause induction in any insect. We identified candidate genes and pathways regulating diapause induction, including a conserved set of genes that are differentially expressed as part of the diapause program in a diverse group of insects. These genes provide candidates whose diapause-associated function can be further interrogated using functional genomics approaches in Ae. albopictus and other insects.
Adult Diapause in Coleoptera
Ivo Hodek
Psyche , 2012, DOI: 10.1155/2012/249081
Abstract: Recent studies dealing with adult (reproductive) diapause in the Coleoptera are reviewed, as a kind of supplement to the classic compendia. In the first two sections, the general characteristics of adult diapause are described and principal terms explained. Original articles dealing with 19 species from nine coleopteran families (Coccinellidae, Chrysomelidae, Bruchidae, Curculionidae, Carabidae, Silphidae, Scolytidae, Scarabaeidae, and Endomychidae) are reviewed. Finally attempts are made at generalisations from the papers reviewed, and hypotheses on diapause evolution are inferred. A polyphenic character of diapause is a prominent feature in C. septempunctata and L. decemlineata, but has been found also in other Coleoptera and in insects generally and often generates voltinism heterogeneity within populations.
Diapause in Calanoid Copepods: within-clutch hatching patterns  [cached]
Bart T. DE STASIO
Journal of Limnology , 2004, DOI: 10.4081/jlimnol.2004.s1.26
Abstract: Diapause is a major life history feature of many invertebrate organisms. Determining the phenology of diapause is critical for understanding survival and reproductive success of individuals as well as the long-term viability of many populations. The time spent in dormancy by individuals and variability among offspring in the duration of dormancy are two important aspects of invertebrate life histories. Some data are available, especially on duration of diapause, for plants and insects, but little information is available concerning variability among offspring in diapause traits. This is especially true for crustacean zooplankton, where essentially no information has been published on duration of diapause or variability among offspring in diapause timing or dynamics. Here I present data on the duration of diapause, and variability among offspring for diapause characteristics. The freshwater calanoid copepod Onychodiaptomus sanguineus, an obligately sexual species, was collected from Bullhead Pond, Rhode Island, U.S.A., and raised under conditions in the laboratory to induce production of diapausing eggs. One hundred clutches of these diapausing eggs (920 total eggs) were incubated for over two years in a full-factorial experiment testing the effects of temperature and photoperiod cycles on the hatching dynamics and duration of diapause. Overall hatching success was highest (approximately 86%) for eggs exposed to simultaneous temperature and photoperiod cycles mimicking natural changes, and was lowest (approximately 20%) when eggs were incubated at constant temperature (4 °C) and in constant dark conditions. The highest fraction of eggs hatched at approximately 550 days of age, but the age of eggs at hatching was highly variable among clutches. There was also large variability within clutches for hatching patterns, with some clutches containing eggs that all hatched synchronously and others in which eggs hatched more continuously throughout the experiment. Treatment conditions significantly affected within-clutch synchrony of hatching, as well as synchrony of the onset of hatching. These results of high within-clutch variability and differences among clutches in diapause dynamics have important implications for our understanding of reproductive success of individuals producing diapausing eggs, parent-offspring conflict, and the evolution of bet-hedging strategies in invertebrates.
Diapause Induction and Termination in Hyphantria cunea (Drury) (Lepidoptera: Arctiinae)  [PDF]
Chao Chen, XiaoTang Wei, HaiJun Xiao, HaiMin He, QinWen Xia, FangSen Xue
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098145
Abstract: The fall webworm, Hyphantria cunea (Drury), enters facultative diapause as a pupa in response to short-day conditions during autumn. Photoperiodic response curves showed that the critical day length for diapause induction was 14 h 30 min, 14 h 25 min and 13 h 30 min at 22, 25 and 28°C, respectively. The photoperiodic responses under non-24 h light–dark cycles demonstrated that night length played an essential role in the determination of diapause. Experiments using a short day length interrupted by a 1-h light pulse exhibited two troughs of diapause inhibition and the effect of diapause inhibition was greater in the early scotophase than in the late scotophase. The diapause-inducing short day lengths of 8, 10 and 12 h evoked greater intensities of diapause than did 13 and 14 h. Diapause can be terminated without exposure to chilling, but chilling at 5°C for 90 and 120 d significantly accelerated diapause development, reduced mortality, and synchronized adult emergence. Additionally, the potential for H. cunea from the temperate region (Qingdao) to emerge and overwinter under field conditions in subtropical regions (Nanchang) of China was evaluated. Pupae that were transferred to Nanchang in early July showed a 60% survival rate and extremely dispersed pupal period (from 12 to 82 days), suggesting that some pupae may undergo summer diapause. Diapausing temperate region pupae that were moved out-of-doors in Nanchang during October showed approximately 20% overwintering survival; moreover, those pupae that overwintered successfully emerged the next spring during a period when their host plants would be available. The results indicate that this moth has the potential to expand its range into subtropical regions of China.
Dynamics of the Microbiota in Response to Host Infection  [PDF]
Clara Belzer, Georg K. Gerber, Guus Roeselers, Mary Delaney, Andrea DuBois, Qing Liu, Vera Belavusava, Vladimir Yeliseyev, Andres Houseman, Andrew Onderdonk, Colleen Cavanaugh, Lynn Bry
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095534
Abstract: Longitudinal studies of the microbiota are important for discovering changes in microbial communities that affect the host. The complexity of these ecosystems requires rigorous integrated experimental and computational methods to identify temporal signatures that promote physiologic or pathophysiologic responses in vivo. Employing a murine model of infectious colitis with the pathogen Citrobacter rodentium, we generated a 2-month time-series of 16S rDNA gene profiles, and quantitatively cultured commensals, from multiple intestinal sites in infected and uninfected mice. We developed a computational framework to discover time-varying signatures for individual taxa, and to automatically group signatures to identify microbial sub-communities within the larger gut ecosystem that demonstrate common behaviors. Application of this model to the 16S rDNA dataset revealed dynamic alterations in the microbiota at multiple levels of resolution, from effects on systems-level metrics to changes across anatomic sites for individual taxa and species. These analyses revealed unique, time-dependent microbial signatures associated with host responses at different stages of colitis. Signatures included a Mucispirillum OTU associated with early disruption of the colonic surface mucus layer, prior to the onset of symptomatic colitis, and members of the Clostridiales and Lactobacillales that increased with successful resolution of inflammation, after clearance of the pathogen. Quantitative culture data validated findings for predominant species, further refining and strengthening model predictions. These findings provide new insights into the complex behaviors found within host ecosystems, and define several time-dependent microbial signatures that may be leveraged in studies of other infectious or inflammatory conditions.
Development of Dengue virus type 2 replicons capable of prolonged expression in host cells
Xiaowu Pang, Mingjie Zhang, Andrew I Dayton
BMC Microbiology , 2001, DOI: 10.1186/1471-2180-1-18
Abstract: Dengue constructs which lack major structural proteins replicate intracellularly in tissue culture. These replicons are capable of prolonged expression of Dengue virus non-structural proteins for at least seven days in culture.Dengue virus genomes lacking major structural proteins can, like other flaviviruses, replicate intracellularly and express virus non-structural proteins with minimal toxicity to host cells. These findings pave the way for the development of dengue virus replicons as a form of live, attenuated virus vaccine.The mosquito-borne flavivirus, Dengue, is estimated to cause in each year 100 million cases of Dengue fever (DF), 500,000 cases of Dengue Hemorrhagic fever (DHF) and 25,000 deaths, with 2.5 billion people at risk [1]. Although a successful vaccine against the prototypical flavivirus, yellow fever (YF) virus, has been in use since the 1930s and vaccines to two other flaviviruses, Japanese encephalitis (JE) virus and tick-borne encephalitis (TBE) virus are currently available, there is as yet no Dengue vaccine approved for use [2].Dengue virus has a typical flavivirus genome structure, as described in Figure 1A. The structural proteins, C, prM (M) and E, are involved in packaging, export and subsequent entry. The non-structural proteins, NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5 include an RNA-directed RNA polymerase, and a protease function involved in cleaving certain positions of the long viral polyprotein which contains all the viral genes [3,4].The four serotypes of Dengue virus ("1" through "4") share approximately 60%–74% amino acid residue identity with one another in the E gene [5] and induce cross-reacting antibodies [6]. However, neutralizing antibodies to the structural proteins of one serotype of Dengue typically not only fail to provide protection against other serotypes, but appear to cause the enhanced replication of virus seen in Dengue hemorrhagic fever, which is generally seen upon reinfection by Dengue virus of a different s
Role of diapause in dispersal and invasion success by aquatic invertebrates  [cached]
Vadim E. PANOV,Piotr I. KRYLOV,Nicoletta RICCARDI
Journal of Limnology , 2004, DOI: 10.4081/jlimnol.2004.s1.56
Abstract: Review of existing literature shows an important role of diapause in dispersal of aquatic invertebrates. There is evidence that among aquatic invertebrates, the role of diapause in dispersal can be important in crustaceans, specifically for species that produce resting eggs. Analysis of dispersal vectors of diapausing species revealed the increasing role of human-mediated vectors of species dispersal during last century (intentional and unintentional introductions, specifically associated with shipping) in comparison with natural vectors (currents, wind, birds). Generally, the role of human-mediated vectors is most important for species dispersal across geographical barriers and into large aquatic ecosystems affected by shipping. Current human-mediated transport vectors increase rates of aquatic species introductions in many orders of magnitude in comparison with historical nature-driven species dispersal rates. Ability to develop diapausing resting stages facilitates species survival during movement across geographical barriers under extreme conditions, such as in ballast tanks of ships. Case studies for invasive species of Cladocera show that some invaders may possess adaptive life cycles, switching to the early prolonged gamogenetic reproduction, which facilitates their invasion success into novel ecosystems and further dispersal by both natural and human-mediated vectors.
Molecular mechanism of diapause in insect (I)
Weihua Xu,Yuanqi Zhang,Ying Wang,Lili Ding,Jing Liu
Science China Life Sciences , 1998, DOI: 10.1007/BF02882732
Abstract: The embryonic diapause of the silkworn,Bombyx mori, is induced by the diapause hormone (DH) which is secreted from the suboesophageal ganglion of pupae. The diapause nature of bivoltine strains uses environmental stimuli as the initial signal to determine the diapause nature. The experiments showed that DH gene expreon is a direct response to the environmend stimulus, such as high incubation temperature. The cDNA from the embryonic stage wa cloned and sequenm analysis showed the cDNA encoding DH. Expmion patterns of the DH gene in embryonic stage are different ar incubation temperatures 15°C and 25°C, suggesting that the incubation tempcreturt as an environmental signal is kept within the body to control the DH gene expmion at the pupal stage, so that the embryonic diapause of next generation can be determined.
Research Progress of the Hormone Regulation of Insect Diapause  [PDF]
XU Jingjing,CHEN Bin,HAO Youjin,SI Fengling
Journal of Chongqing Normal University , 2012,
Abstract: Insects growth and development are controlled by hormone. Diapause is a special development state. In this state, the significant characteristics are metabolism reducing and arrest of development. In the process of diapause development, a variety of hormone tends to create a network by intercoordination. Diapause plays an important regulatory role in diapause development. Insect neuroendocrine hormone is synthesized by neuroendocrine system and acts as upstream factor to affect insect diapause by regulating the synthesis and release of the downstream hormone. The regulation function of diapause hormonepheromone biosynthesis activating neuropeptide and prothoracicotropic hormone in the different type of diapause, insects has been widely studied. Located at the downstream in the network of neuropeptide hormone, the hormones ecdysteroids and juvenile hormone also play important regulatory roles but less studied so far. In addition, the research of hormone receptors will provide an important basis to explain the interaction between hormones; and by adjusting the hormone levels in diapause insect which will provide a new method in the biological control of harmful insects.
Modelling within Host Parasite Dynamics of Schistosomiasis  [PDF]
Edward T. Chiyaka,Gesham Magombedze,Lawrence Mutimbu
Computational and Mathematical Methods in Medicine , 2010, DOI: 10.1080/17486701003614336
Abstract: Schistosomiasis infection is characterized by the presence of adult worms in the portal and mesenteric veins of humans as part of a complex migratory cycle initiated by cutaneous penetration of the cercariae shed by infected freshwater snails. The drug praziquantel is not always effective in the treatment against schistosomiasis at larvae stage. However, our simulations show that it is effective against mature worms and eggs. As a result, the study and understanding of immunological responses is key in understanding parasite dynamics. We therefore introduce quantitative interpretations of human immunological responses of the disease to formulate mathematical models for the within-host dynamics of schistosomiasis. We also use numerical simulations to demonstrate that it is the level of T cells that differentiates between either an effective immune response or some degree of infection. These cells are responsible for the differentiation and recruitment of eosinophils that are instrumental in clearing the parasite. From the model analysis, we conclude that control of infection is much attributed to the value of a function f, a measure of the average number of larvae penetrating a susceptible individual having hatched from an egg released by an infected individual. This agrees with evidence that there is a close association between the ecology, the distribution of infection and the disease.
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