A novel lncRNA PDG1 targets NADP-ME to modulate TCA cycle and JH in Aspongopus chinensis diapause

Diapause is essential for insect survival under adverse environmental conditions and plays a crucial role in regulating reproduction. However, the role of long non-coding RNAs (lncRNAs) in this process remains unclear. In this study, we investigated the function of lncRNAs in the diapause of Aspongopus chinensis. A total of 28,360 lncRNAs were identified across the transcriptomes, with 814 upregulated and 512 downregulated during diapause. Analysis revealed 48 key mRNAs regulated by these lncRNAs, primarily associated with energy metabolism. Among them, the NADP+-dependent malic enzyme (NADP-ME) gene was notably enriched in these pathways. Knockdown of NADP-ME resulted in decreased pyruvate levels and TCA activity. We identified a novel lncRNA, PDG1, which regulates NADP-ME expression, and RNA interference targeting PDG1 increased NADP-ME levels, leading to enhanced pyruvate levels and elevated TCA cycle activity, with dual luciferase assays confirming that PDG1 directly targeted NADP-ME and downregulated its expression. Furthermore, secondary structure analysis revealed that PDG1 exhibited significantly lower free energy compared to NADP-ME, with fewer hairpins and stem-loops. These findings highlight PDG1's critical role in regulating TCA cycle activity by targeting NADP-ME during A. chinensis diapause, revealing a novel mechanism through which lncRNAs modulate metabolic pathways to control insect diapause.

Untangling plastic responses to combined thermal and dietary stress in insects

Animals are exposed to changes in their environmental conditions daily. Such changes will become increasingly more erratic and unpredictable with ongoing climate change. Responses to changing environments are influenced by the genetic architecture of the traits under selection, and modified by a range of physiological, developmental, and behavioural changes resulting from phenotypic plasticity. Furthermore, the interactions between multiple environmental stressors to which organisms are exposed can generate unexpected phenotypic responses. Understanding how genetic and plastic variation contributes to the response to combined environmental stress will be key to predicting how animals will cope with climate change, and ultimately will define their ability to persist. Here, we review the approaches used to explore how animals respond to combined stressors, specifically nutrition and temperature, the physiological mechanisms that underlie such plastic responses, and how genetic variation alters this plasticity.

ets-10p::gfp expression is predictive of dauer formation in daf-16; daf-7 larvae

In adverse conditions, Caenorhabditis elegans larvae can enter the alternative L2d stage. If conditions remain poor, L2d larvae can molt into stress-resistant dauer larvae. The FOXO ortholog daf-16 promotes dauer formation, but daf-16 mutants can enter dauer with incomplete penetrance in combination with a mutation in daf-7 /TGFβ. The degree to which daf-16 ; daf-7 larvae enter L2d is unknown. Here we show that many daf-16 ; daf-7 mutants express intermediate levels of the ets-10p::gfp L2d marker, suggesting incomplete entry into L2d. Furthermore, lack of ets-10p::gfp expression early in the second larval stage partially predicts which daf-16 ; daf-7 larvae will bypass dauer formation.

Genome-wide analysis reveals transcriptional and translational changes during diapause of the Asian corn borer (Ostrinia furnacalis)

BACKGROUND

Diapause, a pivotal phase in the insect life cycle, enables survival during harsh environmental conditions. Unraveling the gene expression profiles of the diapause process helps uncover the molecular mechanisms that underlying diapause, which is crucial for understanding physiological adaptations. In this study, we utilize RNA-seq and Ribo-seq data to examine differentially expressed genes (DEGs) and translational efficiency during diapause of Asian corn borer (Ostrinia furnacalis, ACB).

RESULTS

Our results unveil genes classified as "forwarded", "exclusive", "intensified", or "buffered" during diapause, shedding light on their transcription and translation regulation patterns. Furthermore, we explore the landscape of lncRNAs (long non-coding RNAs) during diapause and identify differentially expressed lncRNAs, suggesting their roles in diapause regulation. Comparative analysis of different types of diapause in insects uncovers shared and unique KEGG pathways. While shared pathways highlight energy balance, exclusive pathways in the ACB larvae indicate insect-specific adaptations related to nutrient utilization and stress response. Interestingly, our study also reveals dynamic changes in the HSP70 gene family and proteasome pathway during diapause. Manipulating HSP protein levels and proteasome pathway by HSP activator or inhibitor and proteasome inhibitor affects diapause, indicating their vital role in the process.

CONCLUSIONS

In summary, these findings enhance our knowledge of how insects navigate challenging conditions through intricate molecular mechanisms.

GC-MS-based Metabolomics Unravels Metabolites across Larval Development and Diapause of a Specialist Insect

Plant-insect interactions are a driving force into ecosystem evolution and community dynamics. Many insect herbivores enter diapause, a developmental arrest stage in anticipation of adverse conditions, to survive and thrive through seasonal changes. Herein, we investigated the roles of medium- to non-polar metabolites during larval development and diapause in a specialist insect herbivore, Chlosyne lacinia, reared on Aldama robusta leaves. Varying metabolites were determined using gas chromatography-mass spectrometry (GC-MS)-based metabolomics. Sesquiterpenes and steroids were the main metabolites putatively identified in A. robusta leaves, whereas C. lacinia caterpillars were characterized by triterpenes, steroids, fatty acids, and long-chain alkanes. We found out that C. lacinia caterpillars biosynthesized most of the identified steroids and fatty acids from plant-derived ingested metabolites, as well as all triterpenes and long-chain alkanes. Steroids, fatty acids, and long-chain alkanes were detected across all C. lacinia instars and in diapausing caterpillars. Sesquiterpenes and triterpenes were also detected across larval development, yet they were not detected in diapausing caterpillars, which suggested that these metabolites were converted to other molecules prior to the diapause stage. Our findings shed light on the chemical content variation across C. lacinia development and diapause, providing insights into the roles of metabolites in plant-insect interactions.

Regulation of forkhead box O transcription factor by insulin signaling pathway controls the reproductive diapause of the lady beetle, Coccinella septempunctata

In biological control programs, knowledge about diapause regulation in natural enemy insects provides important insight for improving long-term storage, transportation, and field adoption of these biological control agents. As a natural predator of agricultural pests, the lady beetle Coccinella septempunctata has been commercially mass-cultured and widely employed in pest management. In some insects, insulin signaling, in conjunction with the downstream transcription factor Forkhead box O (FoxO), are master regulators of multiple physiological processes involved in diapause, but it is unclear whether insulin signaling and FoxO affect the diapause of C. septempunctata. In this study, we use a combination of approaches to demonstrate that insulin signaling and FoxO mediate the diapause response in C. septempunctata. In diapausing beetles, application of exogenous insulin and knocking down expression of CsFoxo with RNA interference (RNAi) both rescued beetles from developmental arrest. In non-diapausing beetles, knocking down expression of the insulin receptor (CsInR) with RNA interference (RNAi) arrested ovarian development and decreased juvenile hormone (JH) content to levels comparable to the diapause state. Taken together, these results suggest that a shutdown of insulin signaling prompts the activation of the downstream FoxO gene, leading to the diapause phenotype.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

A transcriptomic examination of encased rotifer embryos reveals the developmental trajectory leading to long-term dormancy; are they "animal seeds"?

BACKGROUND

Organisms from many distinct evolutionary lineages acquired the capacity to enter a dormant state in response to environmental conditions incompatible with maintaining normal life activities. Most studied organisms exhibit seasonal or annual episodes of dormancy, but numerous less studied organisms enter long-term dormancy, lasting decades or even centuries. Intriguingly, many planktonic animals produce encased embryos known as resting eggs or cysts that, like plant seeds, may remain dormant for decades. Herein, we studied a rotifer Brachionus plicatilis as a model planktonic species that forms encased dormant embryos via sexual reproduction and non-dormant embryos via asexual reproduction and raised the following questions: Which genes are expressed at which time points during embryogenesis? How do temporal transcript abundance profiles differ between the two types of embryos? When does the cell cycle arrest? How do dormant embryos manage energy?

RESULTS

As the molecular developmental kinetics of encased embryos remain unknown, we employed single embryo RNA sequencing (CEL-seq) of samples collected during dormant and non-dormant embryogenesis. We identified comprehensive and temporal transcript abundance patterns of genes and their associated enriched functional pathways. Striking differences were uncovered between dormant and non-dormant embryos. In early development, the cell cycle-associated pathways were enriched in both embryo types but terminated with fewer nuclei in dormant embryos. As development progressed, the gene transcript abundance profiles became increasingly divergent between dormant and non-dormant embryos. Organogenesis was suspended in dormant embryos, concomitant with low transcript abundance of homeobox genes, and was replaced with an ATP-poor preparatory phase characterized by very high transcript abundance of genes encoding for hallmark dormancy proteins (e.g., LEA proteins, sHSP, and anti-ROS proteins, also found in plant seeds) and proteins involved in dormancy exit. Surprisingly, this period appeared analogous to the late maturation phase of plant seeds.

CONCLUSIONS

The study highlights novel divergent temporal transcript abundance patterns between dormant and non-dormant embryos. Remarkably, several convergent functional solutions appear during the development of resting eggs and plant seeds, suggesting a similar preparatory phase for long-term dormancy. This study accentuated the broad novel molecular features of long-term dormancy in encased animal embryos that behave like "animal seeds".

Two distinct aphid diapause strategies: slow development or development arrest

Aphids adapt to unfavourable environmental conditions, such as low temperatures in winter, by laying diapausing eggs that overwinter. Diapause is a stress-resistant and developmentally arrested stage that can be adopted in order to increase the chance of survival in adverse environmental conditions. The diapause process of aphids is still very poorly understood. We followed the development of two species of aphids, Brachycorynella asparagi and Appendiseta robiniae, using the immunostained embryos of the aphids to identify mitotic cell divisions. Two different models of aphid diapause were demonstrated for the first time. In the first strategy, the embryo developed continuously during winter diapause, while in the second case, there was an embryonic arrest. The possibility of slow development of the whole body during diapause is a characteristic feature of aphids. The link to the plant's phenology appears to be a key factor in determining the diapause strategy in aphids.

Methoprene, a Juvenile Hormone Analog, Causes Winter Diapause Elimination in Univoltine Bee Species Osmia bicornis L

Osmia bicornis syn. O. rufa is a univoltine bee species in which adults fly in spring and the offspring overwinter as cocooned imagoes. The flight period of solitary bees is short, so methods of control for development and emergence time are needed to synchronize the activity of managed pollinators with blooming. In our study, we tested the effectiveness of a juvenile hormone analog for the prevention of winter diapause. Bees developed in settled nests outdoors or in the laboratory (22 °C) until the end of the pre-pupa stage, then cocoons were removed from the nest cells and treated with a JH analog-methoprene-during the pupa and young imago stages. Then, bees were activated at 25 °C until the adults left the cocoons. Topical application of methoprene to the cocoon at the pupa or imago stage induced the emergence of some adult bees in the pre-diapause period, while no adults emerged when the bees were not treated with methoprene. Most adults emerged (about 50%) when treated with methoprene on 3-week-old cocooned imagoes. Bees treated in the pupal stage had a lower emergence rate (20-30%), but adult bees emerged earlier. The emergence time of adults for the laboratory group was, on average, from 70 to 91 days, and that for outdoor groups was from 57 to 72 days.

Downregulation of a CT10 regulator of kinase (Crk) promotes the formation of diapause embryos in the brine shrimp Artemia

To survive under harsh environments, embryonic development of Artemia was arrested at the gastrula stage and released as the diapause embryo. Cell cycle and metabolism were highly suppressed in this state of quiescence. However, cellular mechanisms underlying diapause remain largely unclear. In this study, we found that the expression level of a CT10 regulator of kinase-encoding gene (Ar-Crk) in diapause embryos was significantly lower than non-diapause embryos at the early embryogenetic stage of Artemia. Knockdown of Ar-Crk by RNA interference induced formation of diapause embryos, while the control group produced nauplii. Western blot analysis and metabolic assays revealed that the diapause embryos produced by Ar-Crk-knocked-down Artemia had similar characteristics of diapause markers, arrested cell cycle, and suppressed metabolism with those diapause embryos produced by natural oviparous Artemia. Transcriptomic analysis of Artemia embryos revealed knockdown of Ar-Crk induced downregulation of the aurora kinase A (AURKA) signaling pathway, as well as energetic and biomolecular metabolisms. Taken together, we proposed that Ar-Crk is a crucial factor in determining the process of diapause in Artemia. Our results provide insight into the functions of Crk in fundamental regulations such as cellular quiescence.

Fat enough for the winter? Does nutritional status affect diapause?

Many insects enter a dormant state termed diapause in anticipation of seasonal inhospitable conditions. Insects drastically reduce their feeding during diapause. Their reduced nutrient intake is paired with substantial nutrient costs: maintaining basal metabolism during diapause, repairing tissues damaged by adverse conditions, and resuming development after diapause. Many investigators have asked "Does nutrition affect diapause?" In this review, we survey the studies that have attempted to address this question. We propose the term nutritional status, a holistic view of nutrition that explicitly includes the perception, intake, and storage of the great breadth of nutrients. We examine the studies that have sought to test if nutrition affects diapause, trying to identify specific facets of nutritional status that affect diapause phenotypes. Curiously, low quality host plants during the diapause induction phase generally induce diapause, but food deprivation during the same phase generally averts diapause. Using the geometric framework of nutrition to identify specific dietary components that affect diapause may reconcile these contrasting findings. This framework can establish nutritionally permissive space, distinguishing nutrient changes that affect diapause from changes that induce other dormancies. Refeeding is another important experimental technique that distinguishes between diapause and quiescence, a non-diapause dormancy. We also find insufficient evidence for the hypothesis that nutrient stores regulate diapause length and suggest manipulations to investigate the role of nutrient stores in diapause termination. Finally, we propose mechanisms that could interface nutritional status with the diapause program, focusing on combined action of the nutritional axis between the gut, fat body, and brain.

New Perspectives on Sleep Regulation by Tea: Harmonizing Pathological Sleep and Energy Balance under Stress

Sleep, a conservative evolutionary behavior of organisms to adapt to changes in the external environment, is divided into natural sleep, in a healthy state, and sickness sleep, which occurs in stressful environments or during illness. Sickness sleep plays an important role in maintaining energy homeostasis under an injury and promoting physical recovery. Tea, a popular phytochemical-rich beverage, has multiple health benefits, including lowering stress and regulating energy metabolism and natural sleep. However, the role of tea in regulating sickness sleep has received little attention. The mechanism underlying tea regulation of sickness sleep and its association with the maintenance of energy homeostasis in injured organisms remains to be elucidated. This review examines the current research on the effect of tea on sleep regulation, focusing on the function of tea in modulating energy homeostasis through sickness sleep, energy metabolism, and damage repair in model organisms. The potential mechanisms underlying tea in regulating sickness sleep are further suggested. Based on the biohomology of sleep regulation, this review provides novel insights into the role of tea in sleep regulation and a new perspective on the potential role of tea in restoring homeostasis from diseases.

A dynamically structured matrix population model for insect life histories observed under variable environmental conditions

Various environmental drivers influence life processes of insect vectors that transmit human disease. Life histories observed under experimental conditions can reveal such complex links; however, designing informative experiments for insects is challenging. Furthermore, inferences obtained under controlled conditions often extrapolate poorly to field conditions. Here, we introduce a pseudo-stage-structured population dynamics model to describe insect development as a renewal process with variable rates. The model permits representing realistic life stage durations under constant and variable environmental conditions. Using the model, we demonstrate how random environmental variations result in fluctuating development rates and affect stage duration. We apply the model to infer environmental dependencies from the life history observations of two common disease vectors, the southern (Culex quinquefasciatus) and northern (Culex pipiens) house mosquito. We identify photoperiod, in addition to temperature, as pivotal in regulating larva stage duration, and find that carefully timed life history observations under semi-field conditions accurately predict insect development throughout the year. The approach we describe augments existing methods of life table design and analysis, and contributes to the development of large-scale climate- and environment-driven population dynamics models for important disease vectors.

Endocrine Regulation of Lifespan in Insect Diapause

Diapause is a physiological adaptation to conditions that are unfavorable for growth or reproduction. During diapause, animals become long-lived, stress-resistant, developmentally static, and non-reproductive, in the case of diapausing adults. Diapause has been observed at all developmental stages in both vertebrates and invertebrates. In adults, diapause traits weaken into adaptations such as hibernation, estivation, dormancy, or torpor, which represent evolutionarily diverse versions of the traditional diapause traits. These traits are regulated through modifications of the endocrine program guiding development. In insects, this typically includes changes in molting hormones, as well as metabolic signals that limit growth while skewing the organism's energetic demands toward conservation. While much work has been done to characterize these modifications, the interactions between hormones and their downstream consequences are incompletely understood. The current state of diapause endocrinology is reviewed here to highlight the relevance of diapause beyond its use as a model to study seasonality and development. Specifically, insect diapause is an emerging model to study mechanisms that determine lifespan. The induction of diapause represents a dramatic change in the normal progression of age. Hormones such as juvenile hormone, 20-hydroxyecdysone, and prothoracicotropic hormone are well-known to modulate this plasticity. The induction of diapause-and by extension, the cessation of normal aging-is coordinated by interactions between these pathways. However, research directly connecting diapause endocrinology to the biology of aging is lacking. This review explores connections between diapause and aging through the perspective of endocrine signaling. The current state of research in both fields suggests appreciable overlap that will greatly contribute to our understanding of diapause and lifespan determination.