Organelle gain through endosymbiosis has been integral to the origin and diversification of eukaryotes, and, once gained, plastids and mitochondria seem seldom lost. Indeed, discovery of ...nonphotosynthetic plastids in many eukaryotes—notably, the apicoplast in apicomplexan parasites such as the malaria pathogen Plasmodium —highlights the essential metabolic functions performed by plastids beyond photosynthesis. Once a cell becomes reliant on these ancillary functions, organelle dependence is apparently difficult to overcome. Previous examples of endosymbiotic organelle loss (either mitochondria or plastids), which have been invoked to explain the origin of eukaryotic diversity, have subsequently been recognized as organelle reduction to cryptic forms, such as mitosomes and apicoplasts. Integration of these ancient symbionts with their hosts has been too well developed to reverse. Here, we provide evidence that the dinoflagellate Hematodinium sp., a marine parasite of crustaceans, represents a rare case of endosymbiotic organelle loss by the elimination of the plastid. Extensive RNA and genomic sequencing data provide no evidence for a plastid organelle, but, rather, reveal a metabolic decoupling from known plastid functions that typically impede organelle loss. This independence has been achieved through retention of ancestral anabolic pathways, enzyme relocation from the plastid to the cytosol, and metabolic scavenging from the parasite’s host. Hematodinium sp. thus represents a further dimension of endosymbiosis—life after the organelle.
Significance Endosymbiotic organelles are a defining feature of eukaryotes—the last common ancestor and all extant eukaryotes possess at least a mitochondrial derivative. Although mitochondria and plastids are identified with aerobic ATP synthesis and photosynthesis, respectively, their retention by their host cells requires the merging and integration of many, often redundant, metabolic pathways. As a result, complex metabolic interdependencies arise between these formerly independent cells. Complete loss of endosymbiotic organelles, even where aerobic respiration or photosynthesis is lost, is exceedingly difficult, as demonstrated by persistence of organelles throughout secondary anaerobes and parasites. Here, we identify a rare but clear case of plastid loss in a parasitic alga and detail the metabolic disentanglement that was required to achieve this exceptional evolutionary event.
Gene Manipulation in Hydractinia Chrysostomou, Eleni; Febrimarsa; DuBuc, Timothy ...
Methods in molecular biology,
2022, Letnik:
2450
Journal Article
Odprti dostop
The ability to regenerate lost body parts is irregularly distributed among animals, with substantial differences in regenerative potential between and within metazoan phyla. It is widely believed ...that regenerative animal clades inherited some aspects of their capacity to regenerate from their common ancestors but have also evolved new mechanisms that are not shared with other regenerative animals. Therefore, to gain a broad understanding of animal regenerative mechanisms and evolution, a broad sampling approach is necessary. Unfortunately, only few regenerative animals have been established as laboratory models with protocols for functional gene studies. Here, we describe the methods to establish transgenic individuals of the marine cnidarian Hydractinia. We also provide methods for transient gene expression manipulation without modifying the genome of the animals.
Pre-clinical antimicrobial testing is one costly step in antimicrobial drugs development. Costly effective methods in performing the in vitro and in vivo assay as part of pre-clinical stage is ...critical. We reviewed the current development of this stage. We found that standardization of agar diffusion techniques and measurement of minimal inhibitory concentrations in broth dilution methods serve as the primary reference for in vitro antimicrobial testing. In vivo, moral issues, ethics, costs, and the correlation of using animal models with human physiological conditions enforce us to seek alternative systems or animal models. Organ-on-a-Chip (OC) emerges as an ethically sound alternative system, yet in terms of cost and simulation of physiological conditions, there is still much progress to be made. Fruit fly (Drosophila melanogaster) and waxmoth (Galleria mellonella) are currently the main alternative animal models that are more affordable, simple, and ethically sound compared to worms, silkworms, mice, and primates. Artemia spp. and Hydractinia spp. have the potential to become new alternative animal models in simulating microbial infections and the efficacies of the antimicrobial that fight against it in the future.
Abstract
Hydractinia symbiolongicarpus is a pioneering model organism for stem cell biology, being one of only a few animals with adult pluripotent stem cells (known as i-cells). However, the ...unavailability of a chromosome-level genome assembly has hindered a comprehensive understanding of global gene regulatory mechanisms underlying the function and evolution of i-cells. Here, we report the first chromosome-level genome assembly of H. symbiolongicarpus (HSymV2.0) using PacBio HiFi long-read sequencing and Hi-C scaffolding. The final assembly is 483 Mb in total length with 15 chromosomes representing 99.8% of the assembly. Repetitive sequences were found to account for 296 Mb (61%) of the total genome; we provide evidence for at least two periods of repeat expansion in the past. A total of 25,825 protein-coding genes were predicted in this assembly, which include 93.1% of the metazoan Benchmarking Universal Single-Copy Orthologs (BUSCO) gene set. 92.8% (23,971 genes) of the predicted proteins were functionally annotated. The H. symbiolongicarpus genome showed a high degree of macrosynteny conservation with the Hydra vulgaris genome. This chromosome-level genome assembly of H. symbiolongicarpus will be an invaluable resource for the research community that enhances broad biological studies on this unique model organism.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the current pandemic coronavirus disease 2019 (COVID-19). Dysregulated and excessive production of cytokines and ...chemokines, known as cytokine storm, is frequently seen in patients with severe COVID-19 disease and it can provoke a severe systematic inflammation in the patients. The IL-1R/TLRs/IRAKs signaling network is a key pathway in immune cells that plays a central role in regulating innate immunity and inflammatory responses via stimulating the expression and production of various proinflammatory molecules including cytokines. Modulation of IRAKs activity has been proposed to be a promising strategy in the treatment of inflammatory disorders. In this review, we highlight the biochemical properties of IRAKs and their role in regulating inflammatory molecular signaling pathways and discuss the potential targeting of IRAKs to suppress the SARS-CoV-2-induced cytokine storm in COVID-19 patients.
Cell fate stability is essential to maintaining “law and order” in complex animals. However, high stability comes at the cost of reduced plasticity and, by extension, poor regenerative ability. This ...evolutionary trade-off has resulted in most modern animals being rather simple and regenerative or complex and non-regenerative. The mechanisms mediating cellular plasticity and allowing for regeneration remain unknown. We show that signals emitted by senescent cells can destabilize the differentiated state of neighboring somatic cells, reprogramming them into stem cells that are capable of driving whole-body regeneration in the cnidarian Hydractinia symbiolongicarpus. Pharmacological or genetic inhibition of senescence prevents reprogramming and regeneration. Conversely, induction of transient ectopic senescence in a regenerative context results in supernumerary stem cells and faster regeneration. We propose that senescence signaling is an ancient mechanism mediating cellular plasticity. Understanding the senescence environment that promotes cellular reprogramming could provide an avenue to enhance regeneration.
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•Amputation injury induces senescence in a small number of head cells in Hydractinia•Senescent cells persist in the tissue for several hours before being expelled•Signals emitted by senescent cells induce reprogramming of neighboring cells•Reprogrammed cells proliferate and drive whole-body regeneration
Cellular senescence is a form of permanent cell-cycle arrest in animals that is associated with aging and inflammation. Salinas-Saavedra et al. find that, in the absence of resident stem cells, senescent cells can instruct neighboring somatic cells to reprogram into stem cells that drive whole-body regeneration in the cnidarian Hydractinia symbiolongicarpus.
Clonal animals do not sequester a germ line during embryogenesis. Instead, they have adult stem cells that contribute to somatic tissues or gametes. How germ fate is induced in these animals, and ...whether this process is related to bilaterian embryonic germline induction, is unknown. We show that transcription factor AP2 (Tfap2), a regulator of mammalian germ lines, acts to commit adult stem cells, known as i-cells, to the germ cell fate in the clonal cnidarian
mutants lacked germ cells and gonads. Transplanted wild-type cells rescued gonad development but not germ cell induction in
mutants. Forced expression of
in i-cells converted them to germ cells. Therefore, Tfap2 is a regulator of germ cell commitment across germ line-sequestering and germ line-nonsequestering animals.
N6‐methyldeoxyadenosine (6mA) is a chemical alteration of DNA, observed across all realms of life. Although the functions of 6mA are well understood in bacteria and protists, its roles in animal ...genomes have been controversial. We show that 6mA randomly accumulates in early embryos of the cnidarian Hydractinia symbiolongicarpus, with a peak at the 16‐cell stage followed by clearance to background levels two cell cycles later, at the 64‐cell stage—the embryonic stage at which zygotic genome activation occurs in this animal. Knocking down Alkbh1, a putative initiator of animal 6mA clearance, resulted in higher levels of 6mA at the 64‐cell stage and a delay in the initiation of zygotic transcription. Our data are consistent with 6mA originating from recycled nucleotides of degraded m6A‐marked maternal RNA postfertilization. Therefore, while 6mA does not function as an epigenetic mark in Hydractinia, its random incorporation into the early embryonic genome inhibits transcription. In turn, Alkbh1 functions as a genomic 6mA “cleaner,” facilitating timely zygotic genome activation. Given the random nature of genomic 6mA accumulation and its ability to interfere with gene expression, defects in 6mA clearance may represent a hitherto unknown cause of various pathologies.
Synopsis
The presence and functions of N6‐methylation of deoxyadenosine (6mA) in animal genomes are disputed. This study shows that N6‐methyladenosine (m6A)‐decorated maternal RNA is the source of 6mA in cnidarian embryonic genomes, from which it has to be removed for initiation of zygotic transcription.
Rapid degradation of m6A‐marked maternal RNAs generates a nucleotide pool containing m6A.
After NTP‐to‐dNTP conversion by a ribonucleotide reductase, 6mA is randomly incorporated into the embryonic genome.
Genomic 6mA interferes with embryonic transcription.
Removal of 6mA by the 6mA dioxygenase Alkbh1 facilitates timely zygotic genome activation.
N6‐methyladenosine‐decorated maternal RNA is the source of 6mA in the embryonic genome of the cnidarian Hydractinia symbiolongicarpus.
Many animals achieve sperm chromatin compaction and stabilisation by replacing canonical histones with sperm nuclear basic proteins (SNBPs) such as protamines during spermatogenesis. Hydrozoan ...cnidarians and echinoid sea urchins lack protamines and have evolved a distinctive family of sperm-specific histone H2Bs (spH2Bs) with extended N termini rich in SPK(K/R) motifs. Echinoid sperm packaging is regulated by spH2Bs. Their sperm is negatively buoyant and fertilises on the sea floor. Hydroid cnidarians undertake broadcast spawning but their sperm properties are poorly characterised. We show that Hydractinia echinata and H. symbiolongicarpus sperm chromatin possesses higher stability than somatic chromatin, with reduced accessibility to transposase Tn5 integration and to endonucleases in vitro. In contrast, nuclear dimensions are only moderately reduced in mature Hydractinia sperm. Ectopic expression of spH2B in the background of H2B.1 knockdown results in downregulation of global transcription and cell cycle arrest in embryos, without altering their nuclear density. Taken together, SPKK-containing spH2B variants act to stabilise chromatin and silence transcription in Hydractinia sperm with only limited chromatin compaction. We suggest that spH2Bs could contribute to sperm buoyancy as a reproductive adaptation.
is a colonial marine hydroid that shows remarkable biological properties, including the capacity to regenerate its entire body throughout its lifetime, a process made possible by its adult migratory ...stem cells, known as i-cells. Here, we provide an in-depth characterization of the genomic structure and gene content of two
species,
and
, placing them in a comparative evolutionary framework with other cnidarian genomes. We also generated and annotated a single-cell transcriptomic atlas for adult male
and identified cell-type markers for all major cell types, including key i-cell markers. Orthology analyses based on the markers revealed that
's i-cells are highly enriched in genes that are widely shared amongst animals, a striking finding given that
has a higher proportion of phylum-specific genes than any of the other 41 animals in our orthology analysis. These results indicate that
's stem cells and early progenitor cells may use a toolkit shared with all animals, making it a promising model organism for future exploration of stem cell biology and regenerative medicine. The genomic and transcriptomic resources for
presented here will enable further studies of their regenerative capacity, colonial morphology, and ability to distinguish self from nonself.
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