Postembryonic Development Research Articles

Architecture of microtubule cytoskeleton in the hindgut cells of Porcellio scaber

The distribution and orientation of microtubules were investigated in cells of distinct shapes from different hindgut regions of adult Porcellio scaber Latreille, 1804 and during hindgut morphogenesis in late embryonic and early postembryonic development. All hindgut cells of adult P. scaber contain abundant apico-basal microtubules organized in extensive bundles, but the architecture of bundles is specific for distinct cells. In the anterior chamber the architecture of microtubule bundles closely coincides with different shapes of the cells in this hindgut region and are most prominent in hindgut cells associated with extensive muscles. The shape of cells that form the typhlosole and typhlosole channels is particularly complex. In the papillate region the microtubule bundles protrude between the infoldings of apical plasma membrane and the mitochondria are closely aligned along the microtubules, thus the microtubule bundles in the papillate region are likely involved in the stabilization of the apical labyrinth and positioning of mitochondria. During hindgut morphogenesis the apico-basal microtubule bundles are established relatively late, mainly during early postembryonic development. Morphogenesis of the typhlosole is characterized by coinciding changes in cell shape and microtubule arrangement.

The Thermal Tolerance of Springtails in a Tropical Cave, with the Description of a New Coecobrya Species (Collembola: Entomobryidae) from Thailand.

A new species of Collembola in the genus Coecobrya, C. microphthalmasp. nov., is described from a cave environment in Saraburi province, central Thailand. The new species is the second described species of the boneti-group found in the country. It is most similar to C. chompon Nilsai, Lima & Jantarit, 2022, which is also described from a Thai cave. However, the new species is morphologically different from C. chompon in having orange dot pigmentation on its body and a combination of other morphological characteristics such as the number of sublobal hairs on the maxillary outer lobe and the number of medio-sublateral mac on Th. II, Abd. I, Abd. III and Abd. IV and the anterior face of the ventral tube. The morphological comparison of all known boneti species and a key to the world species of Coecobrya of the boneti-group are given. Coecobrya microphthalmasp. nov. was successfully cultured in the laboratory. The thermal tolerance of the new species was studied and tested with seven different temperature experiments (27 °C as a control, 30, 32, 33, 34, 35 and 36 °C). The results showed that C. microphthalmasp. nov. cannot survive at a temperature higher than 32 °C after exposure to the experimental heat for 7 and 14 consecutive days. At 27, 30 and 32 °C, C. microphthalmasp. nov. remained alive and produced eggs, but the duration of egg production and number of egg-laying days significantly declined when the temperature increased (p < 0.001). An interesting aspect of their reproduction concerns temperature. At 32 °C (5 °C above the control temperature), the F1 generation survived, was active and was able to molt to the adult stage. However, specimens were unable to produce the next generation of offspring. For postembryonic development, C. microphthalmasp. nov. required six molts to reach the adult stage. The development rate (from egg to adult) varied and differed significantly between the tested temperatures (p < 0.001). An increase in temperature from the control temperature significantly accelerated the developmental rate from egg to juvenile instars to adult with a statistical significance (p < 0.01). This study is the first attempt that provide information on the impact of increasing temperature on the population dynamics, reproductive capacity and life history of a subterranean tropical Collembola.

The piRNA protein Asz1 is essential for germ cell and gonad development in zebrafish and exhibits differential necessities in distinct types of germ granules.

Germ cells are essential for fertility, embryogenesis, and reproduction. Germline development requires distinct types of germ granules, which contains RNA-protein (RNP) complexes, including germ plasm in embryos, piRNA granules in gonadal germ cells, and the Balbiani body (Bb) in oocytes. However, the regulation of RNP assemblies in zebrafish germline development are still poorly understood. Asz1 is a piRNA protein in Drosophila and mice. Zebrafish Asz1 localizes to both piRNA and Bb granules, with yet unknown functions. Here, we hypothesized that Asz1 functions in germ granules and germline development in zebrafish. We generated asz1 mutant fish to determine the roles of Asz1 in germ cell development. We show that Asz1 is dispensable for somatic development, but essential for germ cell and gonad development. asz1-/- fish developed exclusively as sterile males with severely underdeveloped testes that lacked germ cells. In asz1 mutant juvenile gonads, germ cells undergo extensive apoptosis, demonstrating that Asz1 is essential for germ cell survival. Mechanistically, we provide evidence to conclude that zygotic Asz1 is not required for primordial germ cell specification or migration to the gonad, but is essential during post-embryonic gonad development, likely by suppressing the expression of germline transposons. Increased transposon expression and mis-organized piRNA granules in asz1 mutants, argue that zebrafish Asz1 functions in the piRNA pathway. We generated asz1;tp53 fish to partially rescue ovarian development, revealing that Asz1 is also essential for oogenesis. We further showed that in contrast with piRNA granules, Asz1 is dispensable for Bb granule formation, as shown by normal Bb localization of Buc and dazl. By uncovering Asz1 as an essential regulator of germ cell survival and gonadogenesis in zebrafish, and determining its differential necessity in distinct germ granule types, our work advances our understanding of the developmental genetics of reproduction and fertility, as well as of germ granule biology.

Characterizing executive functioning and associated behaviors in individuals with dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) syndrome.

DYRK1A, a protein kinase located on human chromosome 21, plays a role in postembryonic neuronal development and degeneration. Alterations to DYRK1A have been consistently associated with cognitive functioning and neurodevelopmental disorders (e.g., autism, intellectual disability). However, the broader cognitive and behavioral phenotype of DYRK1A syndrome requires further characterization. Specifically, executive functioning, or cognitive processes that are necessary for goal-directed behavior, has not yet been characterized in this population. Individuals with DYRK1A variants (n = 29; ages 4 to 21 years) were assessed with a standardized protocol with multiple measures of executive functioning: Delis-Kaplan Executive Function Schedule, and chronologically age-appropriate caregiver-report forms of the Behavior Rating Inventory of Executive Function (BRIEF) and Achenbach System of Empirically Based Assessment (ASEBA). We first examined the feasibility and appropriateness of established executive functioning measures among participants with DYRK1A syndrome to inform selection of executive functioning tools in future research. We then characterized executive functioning among the group, including associations with other phenotypic features. Neurocognitive assessments of executive functioning were deemed infeasible due to cognitive and verbal functioning. Caregiver-report revealed elevated executive functioning concerns related to self-monitoring, working memory, and planning/organization on the BRIEF, and attention and ADHD on the CBCL. Only two participants had existing ADHD diagnoses; however, 5 participants (out of 10 participants with data) exceeded the cutoff on the BRIEF, 13 individuals (out of 27 with data) exceeded the cutoff on the ASEBA ADHD subscale, and 18 exceeded the cutoff on the ASEBA attention subscale. There was concordance between ADHD diagnosis and the ASEBA, but not BRIEF. Executive functioning was correlated with nonverbal IQ and autism traits. Objective measures of executive functioning are needed for individuals with intellectual disability who are nonverbal and/or have motor limitations. Diagnostic overshadowing, or the tendency to attribute all problems to intellectual disability and to leave other co-existing conditions, such as executive functioning challenges or ADHD, undiagnosed, is common. Phenotypic characterization of executive functioning is therefore important for our understanding of DYRK1A syndrome and for ensuring that caregivers' concerns are addressed, and individuals receive the clinical services that best meet their needs.

Activin β Is Critical for Larval-Pupal Transition in the 28 Spotted Lady Beetle Henosepilachna vigintioctopunctata.

The activin cascade is activated when a pair of extracellular ligand (Myoglianin, Myo; Activin β, Actβ; Dawdle, Daw) binds to two pairs of transforming growth factor β (TGF) serine-threonine receptor kinases, TGF-β type I (Baboon, Babo) and II receptors. However, the roles of activin way have not well been explored in non-Drosophilid insects. In the present paper, we compared the functions of Activin β (Actβ) ligand and receptor isoform BaboB in post-embryonic development in a defoliating ladybird Henosepilachna vigintioctopunctata. RNA interference (RNAi) for Hvactβ but not Hvbabob upregulated juvenile hormone signal, reduced ecdysone pathway and impaired larval-pupal transformation. The arresting Hvactβ RNAi larvae formed pupa-specific black markings below the larval exuviae. Thus, the impairment of metamorphosis may be caused by failing to complete ecdysis behavior due to nonfunctional muscles. Consistently, larval body sizes were smaller and adult appendages were shorter in the Hvactβ RNAi larvae, in contrast to those in the Hvbabob depleted beetles. Conversely, knockdown of Hvbabob but not Hvactβ changed the pigmentation of adult elytra. Our results suggest that Actβ exerts regulative roles in JH production, ecdysteroidogenesis and organ remodeling, thus contributing to modulate the larva-pupa-adult transformation, through a BaboB independent way in H. vigintioctopunctata.

Experimentally Manipulating the Thyroid Hormone Axis in Zebrafish.

Thyroid hormone (TH) is an endocrine factor with a diverse array of developmental, metamorphic, and metabolic functions conserved across vertebrates. Zebrafish (Danio rerio) are a tractable model for endocrinology research, and recent research efforts focus on the roles of TH in zebrafish morphogenesis, growth and behavior. Several powerful approacheshave been developed in zebrafish to modulatethe TH axis and peripheral sensitivity to the hormone. These approaches include gain- and loss-of-function mutations that target components of the TH signaling pathways, as well as pharmacological treatments to modulate TH synthesis andavailability. Here, we review some of these approaches for generating hypo- and hyperthyroid physiology and phenotypes during post-embryonic zebrafish development. In particular, we focus on a transgenic method of producing hypothyroid fish via metronidazole-based thyroid ablation. This approach can straightforwardly generate large numbers of hypothyroid individuals along with euthyroid sibling controls, and we survey some of the research applications in which this system has been used.

Post-embryonic tail development through molting of the freshwater shrimp Neocaridina denticulata

Post-embryonic tail development through molting of the freshwater shrimp Neocaridina denticulata

English

Abstract Freshwater Astacidea evolved from marine Astacidea, giving rise to four families with remarkable diversity. The Red Swamp Crayfish, Procambarus clarkii (Astacoidea: Cambaridae), is the most economically utilized and invasive species. The morphology of the postembryonic development of this species is described and illustrated for comparison with other Astacidea members. The evolutionary history of the rudimentary vestigial line and filaments on the epipodal plate was examined. Abbreviation of postembryonic stages and the development of telson segmentation of members of the freshwater Astacidea were compared with marine Astacidea. The abbreviation of the larval stage may be related to the phylogenetic relationships among Astacidea members in marine and freshwater environments. The body size of each postembryonic stage was compared among species from each of the four families. Largersized Astacidae and Cambaroididae become independent at Stage II, while smaller-sized Cambaridae and Parastacidae leave maternal care at Stage III. The smallest juveniles belong to Cambaridae in North and Middle America, contributing to the highest species diversity among the four families. Smaller size led to a larger number of juveniles and an extended maternal care period that was related to the higher survival of juveniles. It is proposed that the higher fertility contributed to the evolutionary success of the Cambaridae.

The Identification and Characterization of WOX Family Genes in Coffea arabica Reveals Their Potential Roles in Somatic Embryogenesis and the Cold-Stress Response.

WUSCHEL-related homeobox (WOX) genes play significant roles in plant development and stress responses. Difficulties in somatic embryogenesis are a significant constraint on the uniform seedling production and genetic modification of Coffea arabica, hindering efforts to improve coffee production in Yunnan, China. This study comprehensively analyzed WOX genes in three Coffea species. A total of 23 CaWOXs, 12 CcWOXs, and 10 CeWOXs were identified. Transcriptomic profile analysis indicated that about half of the CaWOX genes were actively expressed during somatic embryogenesis. The most represented CaWOXs were CaWOX2a, CaWOX2b, CaWOX8a, and CaWOX8b, which are suggested to promote the induction and development of the embryogenic callus, whereas CaWOX13a and CaWOX13b are suggested to negatively impact these processes. Co-expression analysis revealed that somatic embryogenesis-related CaWOXs were co-expressed with genes involved in embryo development, post-embryonic development, DNA repair, DNA metabolism, phenylpropanoid metabolism, secondary metabolite biosynthesis, and several epigenetic pathways. In addition, qRT-PCR showed that four WOX genes responded to cold stress. Overall, this study offers valuable insights into the functions of CaWOX genes during somatic embryogenesis and under cold stress. The results suggest that certain WOX genes play distinct regulatory roles during somatic embryogenesis, meriting further functional investigation. Moreover, the cold-responsive genes identified here are promising candidates for further molecular analysis to assess their potential to enhance cold tolerance.

Effect of photoperiod and 20-hydroxyecdysone on post-embryonic development and diapause disruption in Cirina butyrospermi Vuillet (Lepidoptera: Saturniidae) under laboratory conditions

Abstract Cirina butyrospermi (Lepidoptera: Saturniidae), commonly known as the shea caterpillar, is an edible insect in several West African countries. However, this insect is seasonal due to a long pupal diapause. This study therefore aims to explore the potential for mass rearing of C. butyrospermi by determining the role of photoperiod and 20-hydroxyecdysone in disrupting or shortening diapause. Exposure of larval growth to different photoperiod conditions, i.e. L.D. 6:18, L.D. 8:16, L.D. 10:14 and L.D. 12:12, affected larval weight and adult emergence. With respect to the photoperiod treatments applied to larval growth from neonate to fourth instar, caterpillars reared under L.D. 6:18 conditions weighed more than those reared under the other photoperiods. However, photoperiod treatments did not significantly affect the pupation rate. Adult emergence was only observed under L.D. 6:18 photoperiod conditions for a diapause average duration of 140.85 days. The recorded emergence percentage was 38.46 ± 1.33%, and emergences occurred over a period of ten days. When the L.D. 6:18 photoperiod conditions were applied only on the fourth instar larvae, 24.39 ± 1.41% of pupae developed to adults in 34.50 days on average and emergences were grouped in 4 days. Injections of increasing doses of 20-hydroxyecdysone into diapausing pupae resulted in diapause breaking within 23-28 days in 7-47% of treated pupae, depending on the dose of 20-hydroxyecdysone and the pupal weight. Conversely, diapause remained in non-treated pupae during the study period. Short photoperiod and 20-hydroxyecdysone are key drivers for diapause termination in C. butyrospermi. The possible interaction between 20E doses and treated pupae weight provides new insights into the hormone’s efficacy in breaking pupal diapause in C. butyrospermi. While the results need further clarification, they represent a significant step towards mass breeding of this important food insect.

Early-life microRNA signatures in cord blood associated with allergic rhinitis and asthma development.

MicroRNAs (miRNAs) are involved in the biological regulation of asthma and allergies. To investigate the association between cord blood miRNAs and the development of allergic rhinitis and early childhood asthma. miRNAs were sequenced from cord blood of subjects participating in the Vitamin D Antenatal Asthma Reduction Trial. Multivariable miRNA differential expression analyses were performed to examine their association with physician diagnosed asthma and allergic rhinitis by age 3, as well as active asthma status at age 6 years. miRNA signatures were further investigated for their ability to induce human airway smooth muscle cell (HASMC) proliferation in vitro. In a cohort of 389 subjects, elevated cord blood expression of miR-149-5p was associated with both age 3 allergic rhinitis and asthma (log2FC: 1.87 and 1.42, respectively, FDR<0.001), as well as age 6 active asthma status (log2FC: 2.26, FDR<0.001). Higher expressions of miR-99b-5p, miR-125a-5p, and miR-200c-3p were also associated with both diagnosis of allergic rhinitis at age of 3 years and active asthma status at age of 6 (allergic rhinitis: log2FC: 0.6, 0.62, and 1.06, respectively, FDR<0.001; active asthma: log2FC: 0.55, 0.60, 1.10, respectively, FDR<0.001, respectively). Higher expression of miR-145-5p was associated with both new onset asthma after age 3 and active asthma status at age 6 (log2FC: 0.73 and 0.40, FDR<0.001, respectively). These five miRNA signatures target key hubs in the interactome module of 71 genes associated with allergic rhinitis and asthma. Transfection of miR-125a-5p and miR-145-5p into HASMC induced cell proliferation. The dysregulation of cord blood miRNAs at birth are associated with allergic rhinitis and early childhood asthma. The miRNAs that regulate post-embryonic development and immune response may serve as potential biomarkers and preventive targets for asthma.

Complementary and additive functions of TRα and TRβ during intestinal remodeling as revealed by ChIP-Seq analysis on wild type and TR knockout animals

Intestinal structure is drastically changed from fetal to adult form during postembryonic development, a period around birth in mammals. This process is regulated by thyroid hormone (T3) via its receptors, T3 receptor (TR) α and TRβ during anuran metamorphosis. Here, we used intestinal remodeling during Xenopus tropicalis metamorphosis, which serves as a model for human postembryonic development, to identify TR-bound genes and determine the relative contribution to target gene binding by TRα and TRβ. We first examined the localization of TRα and TRβ mRNA during metamorphosis in Xenopus tropicalis and found that TRα was broadly expressed in the intestinal tissues from premetamorphosis to the end of metamorphosis, while TRβ was expressed at low levels during premetamorphosis but was upregulated at the climax of metamorphosis when intestinal stem cells are formed and proliferate. Interestingly, both TR genes were co-expressed in different cell types, including stem cells. Chromatin immunoprecipitation (ChIP)-seq analyses of the intestine from wild type, TRα- or TRβ-knockout premetamorphic tadpoles treated with or without T3 for 18 h identified many TR-bound genes and revealed the effects of individual TR knockout on the binding of target genes by TR. We found that individual TR knockout reduced both the number of TR-bound genes and the extent of TR binding to target genes with TRα knockout had a much more dramatic effect than TRβ knockout. On the other hand, the TR-bound genes were largely common among the three genotypes. These findings suggest that both TRα and TRβ contribute to target binding with TRα having a bigger contribution in premetamorphic intestine.

Experience-dependent, sexually dimorphic synaptic connectivity defined by sex-specific cadherin expression.

Early-life experience influences subsequent maturation and function of the adult brain, sometimes even in a sex-specific manner, but underlying molecular mechanisms are poorly understood. We describe here how juvenile experience defines sexually dimorphic synaptic connectivity in the adult Caenorhabditis elegans nervous system. Starvation of juvenile males disrupts serotonin-dependent activation of the CREB transcription factor in a nociceptive sensory neuron, PHB. CREB acts through a cascade of transcription factors to control expression of an atypical cadherin protein, FMI-1/Flamingo/CELSR. During postembryonic development, FMI-1 promotes and maintains synaptic connectivity of PHB to a command interneuron, AVA, in both sexes, but a serotonin-dependent transcriptional regulatory cassette antagonizes FMI-1 expression in males, thereby establishing sexually dimorphic connectivity between PHB and AVA. A critical regulatory node is the CREB-target LIN-29, a Zn finger transcription factor that integrates four layers of information: sexual specificity, past experience, time and cell-type specificity. Our findings provide the mechanistic details of how an early juvenile experience defines sexually dimorphic synaptic connectivity.

Dynamics of ultrastructural changes in the yolk syncytial layer and its microenvironment during gastrulation and early postembryonic development of &lt;i&gt;Hemichromis Bimaculatus&lt;/i&gt;

BACKGROUND: In fish embryogenesis, the yolk sac is the critical provisional organ, actively functioning during the embryonic and early postembryonic stages. Its primary role is trophic, facilitated in Teleostei by a specialized structure — the yolk syncytial layer (YSL). Ultrastructural transformations of this layer during gastrulation and early postembryonic development, as well as its interaction with migrating muscle fibers and melanophores, are probably necessary for the efficient use of nutrients by the developing embryo. The yolk sac’s role in the embryogenesis of Hemichromis bimaculatus may extend beyond current conceptions. AIM: To study the structural organization of the Jewel Cichlid (H. bimaculatus) yolk sac during the embryonic and early postembryonic development. MATERIALS AND METHODS: The research was involved 22 embryos and larvae of H. bimaculatus from 1 to 7 days after egg laying. The morphological features of the yolk sac were studied using light and transmission electron microscopy. RESULTS: By day 2, the yolk sac was separated from the embryo by the trunk fold. Its main structure was the YSL, containing numerous nuclei, microvilli, mitochondria and phagolysosomes. The morphological features of the YSL were similar to those of the placental symplastotrophoblast and indicated high functional activity. The yolk sac mesenchyme contained blood vessels, migrating melanophores, and muscle fibers. The periderm, covered with a special shell, fuunctioned as the primary skin of the embryo. The transition to exogenous nutrition in Jewel Cichlid larvae was accompanied by a significant decrease in yolk sac size with its subsequent involution. CONCLUSIONS: The trophic function of the yolk sac in H. bimaculatus is mediated by the YSL, which, during gastrulation and postembryonic development, interacts with a number of structures present in the yolk sac wall. Migrating muscle fibers promote activation of yolk granules; accumulation of toxic metabolic products is associated with melanophores. The special structure of the periderm protects both the yolk sac and the embryo from external influences.

DRN facilitates WUS transcriptional regulatory activity by chromatin remodeling to regulate shoot stem cell homeostasis in Arabidopsis.

Shoot stem cells, harbored in the shoot apical meristem (SAM), play key roles during post-embryonic development of Arabidopsis and function as the origin of plant aerial tissues. Multiple transcription factors are involved in the sophisticated transcriptional regulation of stem cell homeostasis, with the WUSCHEL (WUS)/CLAVATA3 (CLV3) negative feedback loop playing a central role. WUS acts as a master regulator in maintaining stem cells through its transcriptional regulatory activity including repressive and activating abilities. Although the interaction between WUS and TOPLESS confers the repressive activity of WUS in transcriptional control, the mechanism by which WUS activates gene expression remains elusive. Here, we showed that DORNRÖSCHEN competitively interacts with WUS and disturbs the WUS homodimer, which recruits BRAHMA to activate CLV3 expression via nucleosome depletion for maintaining the stem cell pool.

Epigenetic memory of temperature sensed during somatic embryo maturation in 2-year-old maritime pine trees.

Embryogenesis is a brief but potentially critical phase in the tree life cycle for adaptive phenotypic plasticity. Using somatic embryogenesis in maritime pine (Pinus pinaster Ait.), we found that temperature during the maturation phase affects embryo development and post-embryonic tree growth for up to three years. We examined whether this somatic stress memory could stem from temperature- and/or development-induced changes in DNA methylation. For this, we developed a 200 Mb custom sequence capture bisulfite analysis of genes and promoters to identify differentially methylated cytosines (DMCs) between temperature treatments (18, 23, and 28°C) and developmental stages (immature and cotyledonary embryos, shoot apical meristem of 2-year-old plants) and investigate if these differences can be mitotically transmitted from embryonic to post-embryonic development (epigenetic memory). We revealed a high prevalence of temperature-induced DMCs in genes (8-14%) compared to promoters (less than 1%) in all 3 cytosine contexts. Developmental DMCs showed a comparable pattern but only in the CG context and with a strong trend towards hypomethylation, particularly in the promoters. A high percentage of DMCs induced by developmental transitions were found memorized in genes (up to 45-50%) and promoters (up to 90%). In contrast, temperature-induced memory was lower and confined to genes after both embryonic (up to 14%) and post-embryonic development (up to 8%). Using stringent criteria, we identified ten genes involved in defense responses and adaptation, embryo development, and chromatin regulation that are candidates for the establishment of a persistent epigenetic memory of temperature sensed during embryo maturation in maritime pine. Here, we provide evidence that DNA methylation marks established during the embryonic phase are transmitted to the post-embryonic plant development phase.

Impact of photobleaching on quantitative, spatio-temporal, super-resolution imaging of mitochondria in live C. elegans larvae

Super-resolution (SR) 3D rendering allows superior quantitative analysis of intracellular structures but has largely been limited to fixed or ex vivo samples. Here we developed a method to perform SR live imaging of mitochondria during post-embryonic development of C. elegans larvae. Our workflow includes the drug-free mechanical immobilisation of animals using polystyrene nanobeads, which has previously not been used for in vivo SR imaging. Based on the alignment of moving objects and global threshold-based image segmentation, our method enables an efficient 3D reconstruction of individual mitochondria. We demonstrate for the first time that the frequency distribution of fluorescence intensities is not affected by photobleaching, and that global thresholding alone enables the quantitative comparison of mitochondria along timeseries. Our composite approach significantly improves the study of biological structures and processes in SR during C. elegans post-embryonic development. Furthermore, the discovery that image segmentation does not require any prior correction against photobleaching, a fundamental problem in fluorescence microscopy, will impact experimental strategies aimed at quantitatively studying the dynamics of organelles and other intracellular compartments in any biological system.

Free long-chain fatty acids trigger early postembryonic development in starved Caenorhabditis elegans by suppressing mTORC1.

Postembryonic development of animals has long been considered an internally predetermined program, while macronutrients were believed to be essential solely for providing biomatters and energy to support this process. However, in this study, by using a nematode Caenorhabditis elegans (abbreviated as C. elegans hereafter) model, we surprisingly discovered that dietary supplementation of palmitic acid alone, rather than other abundant essential nutrients such as glucose or amino acid mixture, was sufficient to initiate early postembryonic development even under complete macronutrient deprivation. Such a development was evidenced by changes in morphology, cellular markers in multiple tissues, behaviors, and the global transcription pattern and it occurred earlier than the well-known early L1 nutrient checkpoint. Mechanistically, palmitic acid did not function as a biomatter/energy provider, but rather as a ligand to activate the nuclear hormone receptor NHR-49/80, leading to the production of an unknown peroxisome-derived secretive hormone in the intestine. This hormonal signal was received by chemosensory neurons in the head, regulating the insulin-like neuropeptide secretion and its downstream nuclear receptor to orchestrate global development. Additionally, the nutrient-sensing hub mTORC1 played a negative role in this process. In conclusion, our data indicate that free fatty acids act as a primary nutrient signal to launch the early development in C. elegans, which suggests that specific nutrients, rather than the internal genetic program, serve as the first impetus for postembryonic development.

Juvenile hormone signaling is indispensable for late embryogenesis in ametabolous and hemimetabolous insects

BackgroundJuvenile hormone (JH) is an insect-exclusive hormone involved in regulating diverse aspects of insect physiology, and the evolution of its diverse function is widely interesting. Studying embryogenesis in basal wingless insects is important to understand the functional evolution of JH; however, experimental studies in this regard are scarce. In this study, we conducted CRISPR/Cas9-mediated knockout (KO) of genes involved in JH biosynthesis and signaling cascades in the ametabolous firebrat, Thermobia domestica. Additionally, we investigated whether the primitive action of JH is conserved in the hemimetabolous cricket, Gryllus bimaculatus.ResultsWe observed that KO of JHAMT, CYP15A1, Met, and Kr-h1 resulted in embryonic lethality in T. domestica. Deprivation of JH or JH signaling arrested the progression of extraembryonic fluid resorption after dorsal closure and hatching, which is consistent with the gene expression pattern showing high Kr-h1 expression in the late embryos of T. domestica. The embryos deficient in JH signaling displayed wrinkled and weak legs. Comparative transcriptome analysis revealed that JH signaling promotes embryonic leg maturation through inducing energy supply and muscle activity, as validated by transmission electron microscopy (TEM). In addition, JH signaling exhibited similar embryonic effects in G. bimaculatus.ConclusionsThis study reveals the indispensable role of JH signaling in facilitating the maturation of terminal tissues during late embryogenesis, as demonstrated by the regulation of leg development, in ametabolous and hemimetabolous insects. These findings further indicate that the embryonic functions of JH evolved earlier than its anti-metamorphic functions during postembryonic development.

Performance of Artificial Diets for Zelus renardii (Hemiptera: Reduviidae) Rearing.

Mass production is a prerequisite for using natural enemies in integrated pest management and organic farming. Natural enemies in agroecosystems include predators that prey on insects, which they can subdue while maintaining adequate pest population densities. The Leafhopper Assassin Bug (LAB), Zelus renardii, can be a natural enemy in agroecosystems, selecting its prey for size and mobility. Some of LAB's prey include Philaenus spumarius (L.), Bactrocera oleae (Rossi), Drosophila suzukii (Matsumura), and Macrohomotoma gladiata Kuwayama, suggesting this reduviid for biocontrol agent in various contexts. We reared LABs for two subsequent broods offering living prey and artificial diets. Our data show that the rearing of Z. renardii is feasible with oligidic, meridic, and holidic artificial formulations. Four artificial diets allowed the complete post-embryonic development of LABs in captivity for two successive generations. The accumulated degree-days (ADDs) accurately predict the growth of LABs based on heat accumulation, estimating that up to three generations could grow per year in captivity at the experimented T°C.