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Marine Pollution Bulletin Jun 2024Paralytic shellfish toxins (PSTs) can pose a serious threat to human health. Among them, saxitoxin (STX) is one of the most potent natural neurotoxins. Here, the copepod...
Paralytic shellfish toxins (PSTs) can pose a serious threat to human health. Among them, saxitoxin (STX) is one of the most potent natural neurotoxins. Here, the copepod Tigriopus japonicus, was exposed to environmentally relevant concentrations (2.5 and 25 μg/L) STX for 48 h. Although no lethal effects were observed at both concentrations, the transcriptome was significantly altered, and displayed a concentration-dependent response. STX exposure decreased the copepod's metabolism and compromised immune defense and detoxification. Additionally, STX disturbed signal transduction, which might affect other cellular processes. STX exposure could inhibit the copepod's chitin metabolism, disrupting its molting process. Also, the processes related to damage repair and protection were up-regulated to fight against high concentration exposure. Collectively, this study has provided an early warning of PSTs for coastal ecosystem not only because of their potent toxicity effect but also their bioaccumulation that can transfer up the food chain after ingestion by copepods.
PubMed: 38870575
DOI: 10.1016/j.marpolbul.2024.116546 -
The Journal of Experimental Biology Jun 2024Lepidosaurian reptiles, particularly snakes, periodically shed the outer epidermal layers of their skin (ecdysis) to restore or enhance vital functions such as...
Lepidosaurian reptiles, particularly snakes, periodically shed the outer epidermal layers of their skin (ecdysis) to restore or enhance vital functions such as regulating water and gaseous exchange, growth, and protection against insult, infection or physical injury. Although many studies have focused on the nature and mechanisms of skin shedding, little attention has been paid to the timing of the first ecdysis in neonates following birth or hatching. A recent study investigated patterns of the time to first postnatal ecdysis in snakes based on a large dataset taken from the literature. The analysis demonstrated patterns in the time to first postnatal ecdysis related to phylogeny as well as several life history traits. While this assessment provides important advances in our knowledge of this topic, data on known biophysical drivers of ecdysis - temperature and humidity - were largely unavailable and were not evaluated. The first postnatal ecdysis of neonatal snakes can be viewed as an adaptive adjustment to the transition from the aqueous environment of the embryo to the aerial environment of the newborn. Hence, the timing of the first postnatal ecdysis is logically influenced by the aerial environment into which a newborn snake or hatchling finds itself. Therefore, in this Commentary, we first emphasize the putative plasticity of ecdysis with respect to epidermal lipids that structure the water permeability barrier and are established or renewed during ecdysis to reduce transepidermal evaporative water loss. We then discuss the likely importance of biophysical variables as influential covariates that need future investigation as potential co-determinants of the timing of first postnatal ecdysis.
Topics: Animals; Snakes; Molting; Time Factors; Animals, Newborn
PubMed: 38869075
DOI: 10.1242/jeb.247536 -
Evolution & Development Jun 2024Molt-based transitions in form are a central feature of insect life that have enabled adaptation to diverse and changing environments. The endocrine regulation of these... (Review)
Review
Molt-based transitions in form are a central feature of insect life that have enabled adaptation to diverse and changing environments. The endocrine regulation of these transitions is well established, but an understanding of their genetic regulation has only recently emerged from insect models. The pupal and adult stages of metamorphosing insects are determined by the stage specifying transcription factors broad-complex (br) and Ecdysone inducible protein 93 (E93), respectively. A probable larval determinant, chronologically inappropriate metamorphosis (chinmo), has just recently been characterized. Expression of these three transcription factors in the metamorphosing insects is regulated by juvenile hormone with ecdysteroid hormones, and by mutual repression between the stage-specific transcription factors. This review explores the hypothesis that variations in the onset, duration, and tissue-specific expression of chinmo, br, and E93 underlie other polyphenisms that have arisen throughout insects, including the castes of social insects, aquatic stages of mayflies, and the neoteny of endoparasites. The mechanisms that constrain how chinmo, br, and E93 expression may vary will also constrain the ways that insect life history may evolve. I find that four types of expression changes are associated with novel insect forms: (1) heterochronic shift in the turnover of expression, (2) expansion or contraction of expression, (3) tissue-specific expression, and (4) redeployment of stage-specific expression. While there is more to be learned about chinmo, br, and E93 function in diverse insect taxa, the studies outlined here show that insect stages are modular units in developmental time and a substrate for evolutionary forces to act upon.
PubMed: 38867484
DOI: 10.1111/ede.12485 -
International Journal of Biological... Jun 2024Silkworm fibroins are natural proteinaceous macromolecules and provide core mechanical properties to silk fibers. The synthesis process of fibroins is posterior silk...
Silkworm fibroins are natural proteinaceous macromolecules and provide core mechanical properties to silk fibers. The synthesis process of fibroins is posterior silk gland (PSG)-exclusive and appears active at the feeding stage and inactive at the molting stage. However, the molecular mechanisms controlling it remain elusive. Here, the silk gland's physiological and nuclear proteomic features were used to characterize changes in its structure and development from molting to feeding stages. The temporal expression profile and immunofluorescence analyses revealed a synchronous transcriptional on-off mode of fibroin genes. Next, the comparative nuclear proteome of the PSG during the last molting-feeding transition identified 798 differentially abundant proteins (DAPs), including 42 transcription factors and 15 epigenetic factors. Protein-protein interaction network analysis showed a "CTCF-FOX-HOX-SOX" association with activated expressions at the molting stage, suggesting a relatively complex and multifactorial regulation of the PSG at the molting stage. In addition, FAIRE-seq verification indicated "closed" and "open" conformations of fibroin gene promoters at the molting and feeding stages, respectively. Such proteome combined with chromatin accessibility analysis revealed the detailed signature of protein factors involved in the temporal regulation of fibroin synthesis and provided insights into silk gland development as well as silk production in silkworms.
PubMed: 38857725
DOI: 10.1016/j.ijbiomac.2024.133028 -
The Journal of Experimental Biology Jun 2024Organisms regularly adjust their physiology and energy balance in response to predictable seasonal environmental changes. Stressors and contaminants have the potential...
Organisms regularly adjust their physiology and energy balance in response to predictable seasonal environmental changes. Stressors and contaminants have the potential to disrupt these critical seasonal transitions. No studies have investigated how simultaneous exposure to methylmercury (MeHg) and food stress affects birds' physiological performance across seasons. We quantified several aspects of energetic performance in song sparrows, Melospiza melodia, exposed, or not, to unpredictable food stress and MeHg in a 2×2 experimental design, over 3 months of exposure during the breeding season, followed by 3 month post-exposure. Birds exposed to food stress had reduced basal metabolic rates and non-significant higher factorial metabolic scope during the exposure period, and had a greater increase in lean mass throughout most of the experimental period. Birds exposed to MeHg had increased molt duration, and increased mass.length-1 ratio of some of their primary feather. Birds exposed to the combined food stress and MeHg treatment often had responses similar to the stress-only or MeHg-only exposure groups, suggesting these treatments affected physiological performance through different mechanisms and resulted in compensatory or independent effects. Because the MeHg and stress variables were selected in candidate models with a delta AICc lower than two but the 95% CI of these variables overlapped zero, we found weak support for MeHg effects on all measures except BMR, and for food stress effects on MMR, factorial metabolic scope and feather mass.length-1 ratio. This suggests that MeHg and stress effects on these measures are statistically identified but not simple and/or were too weak to be detected via linear regression. Overall, combined exposure to ecologically relevant MeHg and unpredictable food stress during the breeding season does not appear to induce extra energetic costs for songbirds in the post-exposure period. However, MeHg effects on molt duration could carry-over across multiple annual cycle stages.
PubMed: 38856174
DOI: 10.1242/jeb.246239 -
Advances in Experimental Medicine and... Jun 2024Lipids are a diverse group of compounds that play several important roles in insect physiology. Among biological lipids, the fundamental category comprises fatty acyl...
Lipids are a diverse group of compounds that play several important roles in insect physiology. Among biological lipids, the fundamental category comprises fatty acyl structures, with significant members being fatty acids (FAs). They play several crucial functions in insect physiology; they are used as the source of energy for flight and play key roles in the insect immune system. The FAs present in the insect cuticle are known to demonstrate antibacterial and antifungal activity and are considered as potential insecticides. The most abundant family of lipids are the glycerolipids, with numerous cellular functions including storage of energy, structural compartmentation of cells and organelles, and important signaling activities required for regulation of physiological processes (i.e., growth, development, reproduction, diapause, and overwintering). The phospholipids are also highly diversified key components of all cell membranes; they can modify cellular components in response to rapid cold-hardening (RCH), enhancing membrane fluidity and improving survival at low temperatures. The sphingolipids are important structural and signaling bioactive compounds, mostly detected in membranes.Insects are sterol-auxotrophs: they do not have genes, which code enzymes converting farnesyl pyrophosphate to squalene. Similarly, to mammals, the production of steroids in insects is regulated by cytochrome P450 enzymes that convert sterols (mostly cholesterol) to hormonally active steroids. The major molting hormone in insects is 20-hydroxyecdysone, and cholesterol is the required precursor; however, several exemptions from this rule have been noted. This manuscript also reviews the roles of prenol lipids, isoprenoids, lipid vitamins, polyketides, and waxes in the vital processes of insects.
PubMed: 38848019
DOI: 10.1007/5584_2024_805 -
Oncology Letters Jul 2024The present study aimed to investigate the anti-leukemic effects of dihydroartemisinin (DHA) on T-cell acute lymphoblastic leukemia (T-ALL) cell lines, Jurkat and...
The present study aimed to investigate the anti-leukemic effects of dihydroartemisinin (DHA) on T-cell acute lymphoblastic leukemia (T-ALL) cell lines, Jurkat and Molt-4, and the underlying mechanisms. Cell Counting Kit-8 was performed to measure cell viability. Cell apoptosis and cell cycle distribution were assessed by flow cytometry. The expression levels of ATF4 and CHOP mRNA were assessed by reverse transcription-quantitative PCR, while the protein abundance of SLC7A11, GPX4, ATF4 and CHOP was determined by western blotting. Moreover, malondialdehyde, glutathione (GSH) and reactive oxygen species (ROS) assays were used to detect the levels of ferroptosis. The results showed that DHA suppressed T-ALL cell viability , and induced cell cycle arrest at S or G/M phase. DHA also induced ROS burst, activated endoplasmic reticulum (ER) stress, disrupted the system Xc-GSH-GSH peroxidase 4 antioxidant system, and increased lipid peroxide accumulation, resulting in cell death. By contrast, the pharmacological inhibition of ferroptosis alleviated DHA-induced cell death, confirming that DHA induces T-ALL cell death via ferroptosis. Mechanistically, the effect of DHA on ferroptosis was partly mediated by downregulating SLC7A11 and upregulating the ATF4-CHOP signaling pathway, which is associated with ER stress. These results indicated that DHA may induce ferroptosis in T-ALL cell lines and could represent a promising therapeutic agent for treating T-ALL.
PubMed: 38846431
DOI: 10.3892/ol.2024.14470 -
BMC Genomics Jun 2024Compound eyes formation in decapod crustaceans occurs after the nauplius stage. However, the key genes and regulatory mechanisms of compound eye development during... (Comparative Study)
Comparative Study
Compound eyes formation in decapod crustaceans occurs after the nauplius stage. However, the key genes and regulatory mechanisms of compound eye development during crustacean embryonic development have not yet been clarified. In this study, RNA-seq was used to investigate the gene expression profiles of Neocaridina denticulata sinensis from nauplius to zoea stage. Based on RNA-seq data analysis, the phototransduction and insect hormone biosynthesis pathways were enriched, and molting-related neuropeptides were highly expressed. There was strong cell proliferation in the embryo prior to compound eye development. The formation of the visual system and the hormonal regulation of hatching were the dominant biological events during compound eye development. The functional analysis of DEGs across all four developmental stages showed that cuticle formation, muscle growth and the establishment of immune system occurred from nauplius to zoea stage. Key genes related to eye development were discovered, including those involved in the determination and differentiation of the eye field, eye-color formation, and visual signal transduction. In conclusion, the results increase the understanding of the molecular mechanism of eye formation in crustacean embryonic stage.
Topics: Animals; Gene Expression Profiling; Compound Eye, Arthropod; Transcriptome; Gene Expression Regulation, Developmental; Decapoda; Eye
PubMed: 38844864
DOI: 10.1186/s12864-024-10453-5 -
Pest Management Science Jun 2024Entomopathogenic fungi, such as Beauveria bassiana, hold promise as biological control agents against insect pests. However, the efficacy of these fungi can be hindered...
BACKGROUND
Entomopathogenic fungi, such as Beauveria bassiana, hold promise as biological control agents against insect pests. However, the efficacy of these fungi can be hindered by insect immune responses. One strategy to enhance fungal virulence is to manipulate host immune by targeting key regulatory molecules like 20-hydroxyecdysone (20E).
RESULTS
In this study, we engineered B. bassiana strains to constitutively express the enzyme ecdysteroid UDP-glucosyltransferase (EGT), which inactivates 20E, a crucial insect molting hormone. The engineered strain Bb::EGT-1 exhibited robust expression of EGT, leading to a significant reduction in insect 20E levels upon infection. Moreover, infection with Bb::EGT-1 resulted in accelerated larval mortality. Immune responses analysis revealed repression of insect immune response genes and decreased phenoloxidase (PO) activity in larvae infected with Bb::EGT-1. Microbiome analysis indicated alterations in bacterial composition within infected insects, with increased abundance observed during infection with Bb::EGT-1. Additionally, the presence of bacteria hindered hyphal emergence from insect cadavers, suggesting a role for microbial competition in fungal dissemination.
CONCLUSIONS
Constitutive expression of EGT in B. bassiana enhances fungal virulence by reducing insect 20E levels, suppressing immune responses, and altering the insect microbiome. These findings highlighted the potential of engineered fungi as effective biocontrol agents against insect pests and provide insights into the complex interactions between entomopathogenic fungi, their hosts, and associated microbes. © 2024 Society of Chemical Industry.
PubMed: 38837657
DOI: 10.1002/ps.8204 -
The Journal of Experimental Biology Jun 2024Once a year, penguins undergo a catastrophic moult, replacing their entire plumage during a fasting period on land or on sea-ice during which time individuals can lose...
Once a year, penguins undergo a catastrophic moult, replacing their entire plumage during a fasting period on land or on sea-ice during which time individuals can lose 45% of their body mass. In penguins, new feather synthesis precedes the loss of old feathers, leading to an accumulation of two feather layers (double coat) before the old plumage is shed. We hypothesized that the combination of the high metabolism required for new feather synthesis and the potentially high thermal insulation linked to the double coat could lead to a thermal challenge requiring additional peripheral circulation to thermal windows to dissipate the extra heat. To test this hypothesis, we measured the surface temperature of different body regions of captive gentoo penguins (Pygoscelis papua) throughout the moult under constant environmental conditions. The surface temperature of the main body trunk decreased during the initial stages of the moult, suggesting greater thermal insulation. In contrast, the periorbital region, a potential proxy of core temperature in birds, increased during these same early moulting stages. The surface temperature of the bill, flipper and foot (thermal windows) tended to initially increase during the moult, highlighting the likely need for extra heat dissipation in moulting penguins. These results raise questions regarding the thermoregulatory capacities of penguins in the wild during the challenging period of moulting on land in the current context of global warming.
Topics: Animals; Spheniscidae; Molting; Feathers; Body Temperature; Body Temperature Regulation; Male; Female
PubMed: 38826104
DOI: 10.1242/jeb.247332