Chromatin regulation and sex determination in Caenorhabditis elegans

Energy as the cornerstone of environmentally driven sex allocation

In recent years, observations of distinct organisms have linked the quality of the environment experienced by a given individual and the sex it will develop. In most described cases, facing relatively harsh conditions resulted in masculinization, while thriving in favorable conditions promoted the development of an ovary. This was shown indistinctively in some species presenting a genetic sex determination (GSD), which were able to sex-reverse, and in species with an environmental sex determination (ESD) system. However, this pattern strongly depends on evolutionary constrains and is detected only when females need more energy for reproduction. Here, I describe the mechanisms involved in this environmentally driven sex allocation (EDSA), which involves two main energy pathways, lipid and carbohydrate metabolism. These pathways act through various enzymes and are not necessarily independent of the previously known transducers of environmental signals in species with ESD: calcium-redox, epigenetic, and stress regulation pathways. Overall, there is evidence of a link between energy level and the sexual fate of individuals of various species, including reptiles, fish, amphibians, insects, and nematodes. As energy pathways are evolutionarily conserved, this knowledge opens new avenues to advance our understanding of the mechanisms that allow animals to adapt their sex according to the local environment.

[Analysis of differentially expressed genes from female and male postparasitic Ovomermis sinensis juveniles]

Mermithidae, as an important natural predator of pests such as Bollworm, has great potential for natural biological control of invasive pests. Unfortunately, the in vitro culture of the nematode has not yet been successful, delaying the commercial application of this pest control method. The key reason for this failure is the inability of the worms to accomplish sex differentiation, sparking a strong interest in this process. Here, we analyzed the differences in gene expression of female and male postparasitic Ovomermis sinensis juveniles by mRNA differential display. In total, 20 gene fragments that had differential expression in male and female worms were isolated, including 8 male- and 12 female-specific ones. Bioinformatics methods were employed to analyze sequences of these fragments, in which ensembl analysis shows 4 fragments have comparable parts with C. elegence's X chromosome, we speculate those fragments are important genes which influence sex differentiation of Ovomermis sinensis, This data provides an idea for further study of the molecular mechanism of sex differentiation in mermithids.

sNASP, a histone H1-specific eukaryotic chaperone dimer that facilitates chromatin assembly

NASP has been described as a histone H1 chaperone in mammals. However, the molecular mechanisms involved have not yet been characterized. Here, we show that this protein is not only present in mammals but is widely distributed throughout eukaryotes both in its somatic and testicular forms. The secondary structure of the human somatic version consists mainly of clusters of alpha-helices and exists as a homodimer in solution. The protein binds nonspecifically to core histone H2A-H2B dimers and H3-H4 tetramers but only forms specific complexes with histone H1. The formation of the NASP-H1 complexes is mediated by the N- and C-terminal domains of histone H1 and does not involve the winged helix domain that is characteristic of linker histones. In vitro chromatin reconstitution experiments show that this protein facilitates the incorporation of linker histones onto nucleosome arrays and hence is a bona fide linker histone chaperone.