Polyps of two moon jellyfish species, Aurelia coerulea and A. relicta, from two Adriatic Sea coastal habitats were incubated under multiple combinations of temperature (14, 21°C), salinity (24, 37 ...ppt) and food regime (9.3, 18.6, 27.9 μg C ind-1 week-1) to comparatively assess how these factors may influence major asexual reproduction processes in the two species. Both species exhibited a shared pattern of budding mode (Directly Budded Polyps: DBP; Stolonal Budded Polyps: SBP), with DBP favoured under low food supply (9.3 μg C ind -1 week-1) and low temperature (14°C), and SBP dominant under high temperature (21°C). However, A. coerulea showed an overall higher productivity than A. relicta, in terms of budding and podocyst production rates. Further, A. coerulea exhibited a wide physiological plasticity across different temperatures and salinities as typical adaptation to ecological features of transitional coastal habitats. This may support the hypothesis that the invasion of A. coerulea across coastal habitats worldwide has been driven by shellfish aquaculture, with scyphistoma polyps and resting stages commonly found on bivalve shells. On the contrary, A. relicta appears to be strongly stenovalent, with cold, marine environmental optimal preferences (salinity 37 ppt, T ranging 14-19°C), corroborating the hypothesis of endemicity within the highly peculiar habitat of the Mljet lake. By exposing A. relicta polyps to slightly higher temperature (21°C), a previously unknown developmental mode was observed, by the sessile polyp regressing into a dispersive, temporarily unattached and tentacle-less, non-feeding stage. This may allow A. relicta polyps to escape climatic anomalies associated to warming of surface layers and deepening of isotherms, by moving into deeper, colder layers. Overall, investigations on species-specific eco-physiological and ontogenetic potentials of polyp stages may contribute to clarify the biogeographic distribution of jellyfish and the phylogenetic relationships among evolutionary related sister clades.
Abstract
Sexual reproduction consists of genome reduction by meiosis and subsequent gamete fusion. The presence of genes homologous to eukaryotic meiotic genes in archaea and bacteria suggests that ...DNA repair mechanisms evolved towards meiotic recombination. However, fusogenic proteins resembling those found in gamete fusion in eukaryotes have so far not been found in prokaryotes. Here, we identify archaeal proteins that are homologs of fusexins, a superfamily of fusogens that mediate eukaryotic gamete and somatic cell fusion, as well as virus entry. The crystal structure of a trimeric archaeal fusexin (Fusexin1 or Fsx1) reveals an archetypical fusexin architecture with unique features such as a six-helix bundle and an additional globular domain. Ectopically expressed Fusexin1 can fuse mammalian cells, and this process involves the additional globular domain and a conserved fusion loop. Furthermore, archaeal fusexin genes are found within integrated mobile elements, suggesting potential roles in cell-cell fusion and gene exchange in archaea, as well as different scenarios for the evolutionary history of fusexins.
Many fungi form complex three-dimensional fruiting bodies, within which the meiotic machinery for sexual spore production has been considered to be largely conserved over evolutionary time. Indeed, ...much of what we know about meiosis in plant and animal taxa has been deeply informed by studies of meiosis in Saccharomyces and Neurospora. Nevertheless, the genetic basis of fruiting body development and its regulation in relation to meiosis in fungi is barely known, even within the best studied multicellular fungal model Neurospora crassa. We characterized morphological development and genome-wide transcriptomics in the closely related species Neurospora crassa, Neurospora tetrasperma, and Neurospora discreta, across eight stages of sexual development. Despite diverse life histories within the genus, all three species produce vase-shaped perithecia. Transcriptome sequencing provided gene expression levels of orthologous genes among all three species. Expression of key meiosis genes and sporulation genes corresponded to known phenotypic and developmental differences among these Neurospora species during sexual development. We assembled a list of genes putatively relevant to the recent evolution of fruiting body development by sorting genes whose relative expression across developmental stages increased more in N. crassa relative to the other species. Then, in N. crassa, we characterized the phenotypes of fruiting bodies arising from crosses of homozygous knockout strains of the top genes. Eight N. crassa genes were found to be critical for the successful formation of perithecia. The absence of these genes in these crosses resulted in either no perithecium formation or in arrested development at an early stage. Our results provide insight into the genetic basis of Neurospora sexual reproduction, which is also of great importance with regard to other multicellular ascomycetes, including perithecium-forming pathogens, such as Claviceps purpurea, Ophiostoma ulmi, and Glomerella graminicola.
Reproductive investment often comes at a cost to longevity, but the mechanisms that underlie these long‐term effects are not well understood. In male vertebrates, elevated testosterone has been shown ...to increase reproductive success, but simultaneously to decrease survival. One factor that may contribute to or serve as a biomarker of these long‐term effects of testosterone on longevity is telomeres, which are often positively related to lifespan and have been shown to shorten in response to reproduction. In this longitudinal study, we measured the effects of experimentally elevated testosterone on telomere shortening in free‐living, male dark‐eyed juncos (Junco hyemalis carolinensis), a system in which the experimental elevation of testosterone has previously been shown to increase reproductive success and reduce survival. We found a small, significant effect of testosterone treatment on telomeres, with testosterone‐treated males exhibiting significantly greater telomere shortening with age than controls. These results are consistent with the hypothesis that increased telomere shortening may be a long‐term cost of elevated testosterone exposure. As both testosterone and telomeres are conserved physiological mechanisms, our results suggest that their interaction may apply broadly to the long‐term costs of reproduction in male vertebrates.
The impact of sex on gene expression across human tissues Oliva, Meritxell; Muñoz-Aguirre, Manuel; Kim-Hellmuth, Sarah ...
Science (American Association for the Advancement of Science),
09/2020, Letnik:
369, Številka:
6509
Journal Article
Recenzirano
Odprti dostop
Many complex human phenotypes exhibit sex-differentiated characteristics. However, the molecular mechanisms underlying these differences remain largely unknown. We generated a catalog of sex ...differences in gene expression and in the genetic regulation of gene expression across 44 human tissue sources surveyed by the Genotype-Tissue Expression project (GTEx, v8 release). We demonstrate that sex influences gene expression levels and cellular composition of tissue samples across the human body. A total of 37% of all genes exhibit sex-biased expression in at least one tissue. We identify cis expression quantitative trait loci (eQTLs) with sex-differentiated effects and characterize their cellular origin. By integrating sex-biased eQTLs with genome-wide association study data, we identify 58 gene-trait associations that are driven by genetic regulation of gene expression in a single sex. These findings provide an extensive characterization of sex differences in the human transcriptome and its genetic regulation.
Populations at range margins of marine organisms are at the front line of climate-induced changes in abiotic factors and are thus particularly susceptible. Especially, macroalgae that are externally ...reproducing rely on optimal environmental conditions for gamete release and subsequent fertilisation. However, the effect of climate change-forced decrease in salinity on these critical life stages has been largely overlooked. We tested the impact of forecasted hyposaline conditions on a marginal population of the rockweed Fucus vesiculosus growing at 5.8 PSU on the Finnish coast of the Baltic Sea. We incubated individuals with receptacles for at least seven days at 2.5, 4.1, 5.8, and 7.2 PSU and determined their gamete release and subsequent fertilisation success. We further tested sperm performance at 3.5, 5.0, and 6.1 PSU. Salinity of 2.5 PSU, which is predicted to occur in the region by the end of this century, reduced egg release. In contrast, sperm and antheridia release were not consistently affected by the different salinities, but the size of sperm swells at 3.5 PSU. Because fertilisation success was drastically reduced at 2.5 and 4.1 PSU, we suggest that sperm performance was compromised such that sperm dysfunction hampered fertilisation success. Our results demonstrate that the forecasted hyposalinity negatively affects egg release and sexual reproduction in F. vesiculosus at its northern distribution limit. This macroalga can probably only withstand the future decrease in salinity when populations proliferate via asexual reproduction.
Phytoplasmas are insect-transmitted phytopathogenic bacteria that can alter plant morphology and the longevity and reproduction rates and behavior of their insect vectors. There are various examples ...of animal and plant parasites that alter the host phenotype to attract insect vectors, but it is unclear how these parasites accomplish this. We hypothesized that phytoplasmas produce effectors that modulate specific targets in their hosts leading to the changes in plant development and insect performance. Previously, we sequenced and mined the genome of Aster Yellows phytoplasma strain Witches’ Broom (AY-WB) and identified 56 candidate effectors. Here, we report that the secreted AY-WB protein 11 (SAP11) effector modulates plant defense responses to the advantage of the AY-WB insect vector Macrosteles quadrilineatus. SAP11 binds and destabilizes Arabidopsis CINCINNATA (CIN)-related TEOSINTE BRANCHED1, CYCLOIDEA, PROLIFERATING CELL FACTORS 1 and 2 (TCP) transcription factors, which control plant development and promote the expression of lipoxygenase (LOX) genes involved in jasmonate (JA) synthesis. Both the Arabidopsis SAP11 lines and AY-WB–infected plants produce less JA on wounding. Furthermore, the AY-WB insect vector produces more offspring on AY-WB–infected plants, SAP11 transgenic lines, and plants impaired in CIN-TCP and JA synthesis. Thus, SAP11-mediated destabilization of CIN-TCPs leads to the down-regulation of LOX2 expression and JA synthesis and an increase in M. quadrilineatus progeny. Phytoplasmas are obligate inhabitants of their plant host and insect vectors, in which the latter transmits AY-WB to a diverse range of plant species. This finding demonstrates that pathogen effectors can reach beyond the pathogen–host interface to modulate a third organism in the biological interaction.
The worldwide distribution and extensive genetic diversity of the whitefly Bemisia tabaci has long been recognized. However, whether B. tabaci is a complex species or a species complex has been a ...subject of debate. Recent phylogenetic analyses suggest that B. tabaci is a cryptic species complex composed of at least 24 morphologically indistinguishable species. Here, we conducted crossing experiments and demonstrated reproductive incompatibility among three of the 24 putative species. Our data and those of previously reported crossing experiments among various putative species of B. tabaci were collated to reveal the pattern of reproductive isolation. The combined results provide strong support to the proposition that B. tabaci is a cryptic species complex.
Autophagy is ubiquitously present in eukaryotes. During this process, intracellular proteins and some waste organelles are transported into lysosomes or vacuoles for degradation, which can be reused ...by the cell to guarantee normal cellular metabolism. However, the function of autophagy-related (ATG) proteins in oomycetes is rarely known. In this study, we identified an autophagy-related gene,
encoding a 514-amino-acid protein in
which is the most destructive pathogen of litchi. The transcriptional level of
was relatively higher in mycelium, sporangia, zoospores and cysts. We generated
knockout mutants using CRISPR/Cas9 technology. The
Δ
mutants were significantly impaired in autophagy and vegetative growth. We further found that the Δ
mutants displayed decreased branches of sporangiophore, leading to impaired sporangium production. PlATG6a is also involved in resistance to oxidative and salt stresses, but not in sexual reproduction. The transcription of peroxidase-encoding genes was down-regulated in Δ
mutants, which is likely responsible for hypersensitivity to oxidative stress. Compared with the wild-type strain, the Δ
mutants showed reduced virulence when inoculated on the litchi leaves using mycelia plugs. Overall, these results suggest a critical role for PlATG6a in autophagy, vegetative growth, sporangium production, sporangiophore development, zoospore release, pathogenesis and tolerance to salt and oxidative stresses in
.
Aspergillus flavus colonizes agricultural commodities worldwide and contaminates them with carcinogenic aflatoxins. The high genetic diversity of A. flavus populations is largely due to sexual ...reproduction characterized by the formation of ascospore-bearing ascocarps embedded within sclerotia. A. flavus is heterothallic and laboratory crosses between strains of the opposite mating type produce progeny showing genetic recombination. Sclerotia formed in crops are dispersed onto the soil surface at harvest and are predominantly produced by single strains of one mating type. Less commonly, sclerotia may be fertilized during co-infection of crops with sexually compatible strains. In this study, laboratory and field experiments were performed to examine sexual reproduction in single-strain and fertilized sclerotia following exposure of sclerotia to natural fungal populations in soil. Female and male roles and mitochondrial inheritance in A. flavus were also examined through reciprocal crosses between sclerotia and conidia. Single-strain sclerotia produced ascospores on soil and progeny showed biparental inheritance that included novel alleles originating from fertilization by native soil strains. Sclerotia fertilized in the laboratory and applied to soil before ascocarp formation also produced ascospores with evidence of recombination in progeny, but only known parental alleles were detected. In reciprocal crosses, sclerotia and conidia from both strains functioned as female and male, respectively, indicating A. flavus is hermaphroditic, although the degree of fertility depended upon the parental sources of sclerotia and conidia. All progeny showed maternal inheritance of mitochondria from the sclerotia. Compared to A. flavus populations in crops, soil populations would provide a higher likelihood of exposure of sclerotia to sexually compatible strains and a more diverse source of genetic material for outcrossing.
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