Small fish use the hypoxic pelagic zone as a refuge from predators

相似文献   

Interpopulation hybridization generates meiotically stable rDNA epigenetic variants in allotetraploid Tragopogon mirus

Uniparental silencing of 35S rRNA genes (rDNA), known as nucleolar dominance (ND), is common in interspecific hybrids. Allotetraploid Tragopogon mirus composed of Tragopogon dubius (d) and Tragopogon porrifolius (p) genomes shows highly variable ND. To examine the molecular basis of such variation, we studied the genetic and epigenetic features of rDNA homeologs in several lines derived from recently and independently formed natural populations. Inbred lines derived from T. mirus with a dominant d‐rDNA homeolog transmitted this expression pattern over generations, which may explain why it is prevalent among natural populations. In contrast, lines derived from the p‐rDNA dominant progenitor were meiotically unstable, frequently switching to co‐dominance. Interpopulation crosses between progenitors displaying reciprocal ND resulted in d‐rDNA dominance, indicating immediate suppression of p‐homeologs in F₁ hybrids. Original p‐rDNA dominance was not restored in later generations, even in those segregants that inherited the corresponding parental rDNA genotype, thus indicating the generation of additional p‐rDNA and d‐rDNA epigenetic variants. Despite preserved intergenic spacer (IGS) structure, they showed altered cytosine methylation and chromatin condensation patterns, and a correlation between expression, hypomethylation of RNA Pol I promoters and chromatin decondensation was apparent. Reversion of such epigenetic variants occurred rarely, resulting in co‐dominance maintained in individuals with distinct genotypes. Generally, interpopulation crosses may generate epialleles that are not present in natural populations, underlying epigenetic dynamics in young allopolyploids. We hypothesize that highly expressed variants with distinct IGS features may induce heritable epigenetic reprogramming of the partner rDNA arrays, harmonizing the expression of thousands of genes in allopolyploids.     

Conditions at the breeding grounds and migration strategy shape different moult patterns of two populations of Eurasian golden plover Pluvialis apricaria

Events in the life cycle of migrant birds are generally time‐constrained. Moult, together with breeding and migration, is the most energetically demanding annual cycle stages, but it is the only stage that can be scheduled at different times of the year. However, it is still not fully understood what factors determine this scheduling. We compare the timing of primary feather moult in relation to breeding and migration between two populations of Eurasian golden plover Pluvialis apricaria, the continental population breeding in Scandinavia and in N Russia that migrates to the Netherlands and southern Europe, and the Icelandic population that migrates mainly to Ireland and western UK. Moult was studied at the breeding grounds (N Sweden, N Russia, Iceland) and at stopover and wintering sites (S Sweden, the Netherlands). In both populations, primary moult overlapped with incubation and chick rearing, and females started on average 9 d later than males. Icelandic plovers overlapped moult with incubation to a larger extent and stayed in the breeding grounds until primary moult was completed. In contrast, continental birds only moulted the first 5–7 primaries at the breeding grounds and completed moult in stopover and wintering areas, such as S Sweden and the Netherlands. This overlap, although rare in birds, can be understood from an annual cycle perspective. Icelandic plovers presumably need to initiate moult early in the season to be able to complete it at the breeding grounds. The latter is not possible for continental plovers as their breeding season is much shorter due to a harsher climate. Additionally, for this population, moulting all the primaries at the stopover/wintering site is also not possible as too little time would remain to prepare for cold‐spell movements. We conclude that environmental conditions and migration strategy affect the annual scheduling of primary feather moult in the Eurasian golden plover.     

Senescence and declining reproductive potential: Insight into molecular mechanisms through testicular metabolomics

Aging is associated with structural and functional changes in the organism that result in the declining of its functioning. Postponed parenthood has renewed the interest in age-related decline of testicular function and male fertility. Still, little is known about the molecular mechanisms associated with testicular senescence and related decline of fertility. Here we sought to elucidate the molecular basis of metabolic changes associated with testicular aging and reproductive potential using an NMR-based metabolomics approach. Testicular metabolic profiles of rats from 3 to 24?months-of-age were analysed. An age-associated decrease in most antioxidant metabolites, like betaine, creatine and glutathione was observed. Amino acid content changed as early as 6?months-of-age, with an increase in branched chain and aromatic amino acids, accompanied by decrease of nucleotide synthesis (IMP, CMP, ATP). Testicular content of phospholipid precursors (choline, ethanolamine, myo-inositol, glycerol) increased with advanced age and was accompanied by a decrease in the levels of their phosphorylated products, suggesting compromised spermatogenesis. This is the first metabolomics study of testicular tissue of aged rats and we were able to identify metabolites associated with reproductive maturity from the onset to senescence. Our results provide evidence for an influence of aging on global testicular metabolome, as early as 6?months-of-age, with a profound alteration of several key metabolic pathways associated with the male reproductive potential.     

Dutch Resolution of a configurationally stable [5]helquat

Synthesis and nontrivial optical resolution of a helicene‐like dication, helquat 1 , has been accomplished. Starting with gram scale of the racemic helquat 1 sample, Dutch Resolution using family of 3 tartrate anions was key to achieve successful separation of M and P helical enantiomers of 1 . Hundreds of milligrams of each enantiomer of this configurationally stable C₂‐symmetric helquat have been obtained. Racemization barrier of 1 has been determined. To our knowledge this is the first report on Dutch Resolution performed with a helicene‐like compound. Moreover, there are no literature precedents for Dutch Resolution of chiral quaternary ammonium cations.     

NCAM1 is the Target of miRNA-572: Validation in the Human Oligodendroglial Cell Line

The neural cell adhesion molecule 1 (NCAM1) is a fundamental protein in cell–cell interaction and in cellular developmental processes, and its dysregulation is involved in a number of diseases including multiple sclerosis. Studies in rats suggest that the modulation of NCAM1 expression is regulated by miRNA-572, but no data are available confirming such interaction in the human system. We analyzed whether this is the case using a human oligodendroglial cell line (MO3.13). MO3.13 cells were transfected with miRNA-572 mimic and inhibitor separately; NCAM1 mRNA and protein expression levels were analyzed at different time points after transfection. Results indicated that NCAM1 expression is increased after transfection with miRNA-572 inhibitor, whereas it is decreased after transfection with the mimic (p < 0.005). The interaction between NCAM1 and miRNA-572 was subsequently confirmed in a Vero cell line that does not express NCAM1, by luciferase assay after transfection with NCAM1. These results confirm that miRNA-572 regulates NCAM1 and for the first time demonstrate that this interaction regulates NCAM1 expression in human cells. Data herein also support the hypothesis that miRNA-572 is involved in diseases associated with NCAM1 deregulation, suggesting its possible use as a biomarker in these diseases.     

Water mite (Acari: Hydrachnidia) diversity and distribution in undisturbed Dinaric karst springs

Large undisturbed karst springs in the Dinaric region are particularly interesting and extremely valuable and rare ecosystems, housing diverse and yet undiscovered water mite species. The complex life history traits of water mites include several life stages that are interconnected with other freshwater arthropod groups, making them important components of freshwater fauna. This study examined whether the differences in water mite assemblages between Mediterranean and alpine karst springs were driven by seasonal and/or regional changes in environmental conditions. The first ecological data on water mite dynamics and distribution in the Dinaric region of Croatia are presented. Water mites were represented by 11 taxa, decreasing in taxon richness from alpine to Mediterranean springs. Spatial patterns of water mite assemblages at the regional scale were best explained by water temperature, dissolved oxygen and water velocity. Pseudotorrenticola rhynchota and Oxus setosus were exclusively found in springs with higher water temperature and velocity, whereas the genera Aturus sp. and Woolastookia rotundifrons were exclusively recorded in the alpine springs, where oxygen concentrations were significantly higher. Atractides sp., Lebertia sp. and Sperchon sp. were recorded in most springs. Water mite abundances had a summer peak in the Mediterranean region, whereas two smaller peaks were observed in the spring and fall in the alpine region. Regional differences in the seasonality of water mite abundance were most likely patterned by the emergence of insect crenofauna.