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Oxygen is essential for most life forms. Insufficient oxygen supply can disrupt homeostasis and compromise survival, and hypoxia-induced cardiovascular failure is fatal in many animals, including humans. However, certain species have adapted and evolved to cope with hypoxic environments and are therefore good models for studying the regulatory mechanisms underlying responses to hypoxia. Here, we explored the physiological and molecular responses of the cardiovascular system in two closely related hypoxia-adapted species with different life histories, namely, Qinghai voles (Neodon fuscus) and Brandt’s voles (Lasiopodomys brandtii), under hypoxic (10% O2 for 48 h) and normoxic (20.9% O2 for 48 h) exposure. Kunming mice (Mus musculus) were used for comparison. Qinghai voles live in plateau areas under hypoxic conditions, whereas Brandt’s voles only experience periodic hypoxia. Histological and hematological analyses indicated a strong tolerance to hypoxia in both species, but significant cardiac tissue damage and increased blood circulation resistance in mice exposed to hypoxia. Comparative transcriptome analysis revealed enhanced oxygen transport efficiency as a coping mechanism against hypoxia in both N. fuscus and L. brandtii, but with some differences. Specifically, N. fuscus showed up-regulated expression of genes related to accelerated cardiac contraction and angiogenesis, whereas L. brandtii showed significant up-regulation of erythropoiesis-related genes. Synchronized up-regulation of hemoglobin synthesis-related genes was observed in both species. In addition, differences in cardiometabolic strategies against hypoxia were observed in the rodents. Notably, M. musculus relied on adenosine triphosphate (ATP) generation via fatty acid oxidation, whereas N. fuscus shifted energy production to glucose oxidation under hypoxic conditions and L. brandtii employed a conservative strategy involving down-regulation of fatty acid and glucose oxidation and a bradycardia phenotype. In conclusion, the cardiovascular systems of N. fuscus and L. brandtii have evolved different adaptation strategies to enhance oxygen transport capacity and conserve energy under hypoxia. Our findings suggest that the coping mechanisms underlying hypoxia tolerance in these closely related species are context dependent.
In vitro production of functional gametes can revolutionize reproduction by reducing generation intervals and accelerating genetic breeding in aquaculture, especially in fish with relatively long generations. Nevertheless, functional sperm production from in vitro-cultured spermatogonia remains a challenge in most aquaculture fish. In this study, we isolated and characterized premeiotic spermatogonia from marine four-eyed sleepers (Bostrychus sinensis), which are prone to ovotesticular or sterile testicular development, and induced the differentiation of the spermatogonia into flagellated sperm in a three-dimensional (3D) culture system. Artificial insemination indicated that the in vitro-derived sperm were capable of fertilizing mature oocytes to develop into normal larvae. Furthermore, melatonin significantly promoted spermatogonia proliferation and differentiation through the ERK1/2 signaling pathway, and thus increased the efficiency in functional sperm production. The 3D culture system and resulting functional sperm hold great promise for improving the genetic breeding of aquaculture fish.
Cell division and differentiation after egg fertilization are critical steps in the development of embryos from single cells to multicellular individuals and are regulated by DNA methylation via its effects on gene expression. However, the mechanisms by which DNA methylation regulates these processes in insects remain unclear. Here, we studied the impacts of DNA methylation on early embryonic development in Bombyx mori. Genome methylation and transcriptome analysis of early embryos showed that DNA methylation events mainly occurred in the 5' region of protein metabolism-related genes. The transcription factor gene zinc finger protein 615 (ZnF615) was methylated by DNA methyltransferase 1 (Dnmt1) to be up-regulated and bind to protein metabolism-related genes. Dnmt1 RNA interference (RNAi) revealed that DNA methylation mainly regulated the expression of nonmethylated nutrient metabolism-related genes through ZnF615. The same sites in the ZnF615 gene were methylated in ovaries and embryos. Knockout of ZnF615 using CRISPR/Cas9 gene editing decreased the hatching rate and egg number to levels similar to that of Dnmt1 knockout. Analysis of the ZnF615 methylation rate revealed that the DNA methylation pattern in the parent ovary was maintained and doubled in the offspring embryo. Thus, Dnmt1-mediated intragenic DNA methylation of the transcription factor ZnF615 enhances its expression to ensure ovarian and embryonic development.
Spiders are among the most varied terrestrial predators, with highly diverse morphology, ecology, and behavior. Morphological and molecular data have greatly contributed to advances in the phylogeny and evolutionary dynamics of spiders. Here, we performed comprehensive mitochondrial phylogenomics analysis on 78 mitochondrial genomes (mitogenomes) representing 29 families; of these, 23 species from eight families were newly generated. Mesothelae retained the same gene arrangement as the arthropod ancestor (Limulus polyphemus), while Opisthothelae showed extensive rearrangement, with 12 rearrangement types in transfer RNAs (tRNAs) and control region. Most spider tRNAs were extremely truncated and lacked typical dihydrouridine or TΨC arms, showing high tRNA structural diversity; in particular, trnS1 exhibited anticodon diversity across the phylogeny. The evolutionary rates of mitochondrial genes were potentially associated with gene rearrangement or truncated tRNAs. Both mitogenomic sequences and rearrangements possessed phylogenetic characteristics, providing a robust backbone for spider phylogeny, as previously reported. The monophyly of suborder, infraorder, retrolateral tibial apophysis clade, and families (except for Pisauridae) was separately supported, and high-level relationships were resolved as (Mesothelae, (Mygalomorphae, (Entelegynae, (Synspermiata, Hypochilidae)))). The phylogenetic positions of several families were also resolved (e.g., Eresidae, Oecobiidae and Titanoecidae). Two reconstructions of ancestral web type obtained almost identical results, indicating that the common ancestor of spiders likely foraged using a silk-lined burrow. This study, the largest mitochondrial phylogenomics analysis of spiders to date, highlights the usefulness of mitogenomic data not only for providing efficient phylogenetic signals for spider phylogeny, but also for characterizing trait diversification in spider evolution.
Heterosis is a common phenomenon in plants and animals with diverse underlying mechanisms. Here, we applied two widely used silkworm hybrid systems and performed multi-omics analysis to identify possible intrinsic associations between different hybrid strategies and epigenetic mechanisms with silkworm heterosis. We found significant differences in the silk gland transcriptomic landscape between the two systems, including differentially expressed genes and expression patterns in the hybrid offspring compared to their parents. In the quaternary hybrid system, hybrid vigor was primarily due to up-regulated genes and the parent-dominant up-regulated expression pattern, involving multiple transport processes, cellular nitrogen compound catabolism, glucose metabolism, and tricarboxylic acid cycle. In the binary system, hybrid vigor was mainly due to the down-regulated genes and transgressively down-regulated expression pattern, mainly involving basic nitrogen synthesis metabolism and body function. We also demonstrated that DNA methylation may affect hybrid vigor by regulating the expression of several heterosis-related genes. Thus, this study revealed two alternative mechanisms that may contribute to silkworm heterosis, both of which facilitate the efficient utilization of energy and nitrogen for silk production.
Letter to the editor
Bats are reservoirs of various viruses. The widely distributed cave nectar bat (Eonycteris spelaea) is known to carry both filoviruses and coronaviruses. However, the potential transmission of theses bat viruses to humans is not fully understood. In this study, we tracked 16 E. spelaea bats in Mengla County, Yunnan Province, China, using miniaturized GPS devices to investigate their movements and potential contact with humans. Furthermore, to determine the prevalence of coronavirus and filovirus infections, we screened for the nucleic acids of the Měnglà virus (MLAV) and two coronaviruses (GCCDC1-CoV and HKU9-CoV) in anal swab samples taken from bats and for antibodies against these viruses in human serum samples. None of the serum samples were found to contain antibodies against the bat viruses. The GPS tracking results showed that the bats did not fly during the daytime and rarely flew to residential areas. The foraging range of individual bats also varied, with a mean cumulative nightly flight distance of 25.50 km and flight speed of up to 57.4 km/h. Taken together, these results suggest that the risk of direct transmission of GCCDC1-CoV, HKU9-CoV, and MLAV from E. spelaea bats to humans is very low under natural conditions.
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