摘要: The polysaccharide chitin is a major scaffolding molecule in the insect cuticle. In order to be functional, both chitin amounts and chitin organization have been shown to be important parameters. Despite great advances in the past decade, the molecular mechanisms of chitin synthesis and organization are not fully understood. Here, we have characterized the function of the Chitinase 6 (Cht6) in the formation of the wing, which is a simple flat cuticle organ, in the fruit fly Drosophila melanogaster. Reduction of Cht6 function by RNA interference during wing development does not affect chitin organization, but entails a thinner cuticle suggesting reduced chitin amounts. This phenotype is opposed to the one reported recently to be caused by reduction of Cht10 expression. Probably as a consequence, cuticle permeability to xenobiotics is enhanced in Cht6-less wings. We also observed massive deformation of these wings. In addition, the shape of the abdomen is markedly changed upon abdominal suppression of Cht6. Finally, we found that suppression of Cht6 transcript levels influences the expression of genes coding for enzymes of the chitin biosynthesis pathway. This finding indicates that wing epidermal cells respond to activity changes of Cht6 probably trying to adjust chitin amounts. Together, in a working model, we propose that Cht6-introduced modifications of chitin are needed for chitin synthesis to proceed correctly. Cuticle thickness, according to our hypothesis, is in turn required for correct organ or body part shape. The molecular mechanisms of this processes shall be characterized in the future.

摘要: With the completion of the draft assembly of the giant panda genome sequence, RNA sequencing technology has been widely used in genetic research on giant pandas. We used RNA-seq to examine black and white hair follicle samples from adult pandas. By comparison with the giant panda genome, 75 963 SNP loci were labeled, 2426 differentially expressed genes (DEGs) were identified, and 2029 new genes were discovered, among which 631 were functionally annotated. A cluster analysis of the DEGs showed that they were mainly related to the Wnt signaling pathway, ECM-receptor interaction, the p53 signaling pathway, and ribosome processing. The enrichment results showed that there were significant differences in the regulatory networks of hair follicles with different colors during the transitional stage of hair follicle resting growth, which may play a regulatory role in melanin synthesis during growth. In conclusion, our results provide new insights and more data support for research on the color formation in giant pandas.

摘要: Evaluating the fitness of hybrids can provide important insights into genetic differences between species or diverging populations. We focused on surface- and cave-ecotypes of the widespread Atlantic molly Poecilia mexicana and raised F1 hybrids of reciprocal crosses to sexual maturity in a common-garden experiment. Hybrids were reared in a fully factorial 2 x 2 design consisting of lighting (light vs. darkness) and resource availability (high vs. low food). We quantified survival, ability to realize their full reproductive potential (i.e., completed maturation for males and 3 consecutive births for females) and essential life-history traits. Compared to the performance of pure cave and surface fish from a previous experiment, F1s had the highest death rate and the lowest proportion of fish that reached their full reproductive potential. We also uncovered an intriguing pattern of sex-specific phenotype expression, because male hybrids expressed cave molly life histories, while female hybrids expressed surface molly life histories. Our results provide evidence for strong selection against hybrids in the cave molly system, but also suggest a complex pattern of sex-specific (opposing) dominance, with certain surface molly genes being dominant in female hybrids and certain cave molly genes being dominant in male hybrids.

摘要: The microbial consortium within an organism is crucial for its development and immune status. Alteration of the host microbiome by antibiotics or antinutritional factors may contribute to increased disease susceptibility. Here, we investigated whether exposure to different microbes could influence zebrafish larval microbiota composition and modulate their immune response towards a saponin challenge. Adult zebrafish were exposed to the antibiotic oxytetracycline (OxyT) or control tank water and their intestinal content was harvested after 30 h (24 h exposure, 6 h wash-out). Subsequently, zebrafish embryos were exposed to either OxyT-treated content or non-treated content from 3 to 6 days post fertilization (dpf). At 6 dpf part of the group received a saponin challenge until 8 dpf. Zebrafish larvae exposed to OxyT-treated adult gut content (3-6 dpf) showed an altered microbiota composition compared to controls. Interestingly, larvae exposed to saponin-treated OxyT-content showed fewer macrophages (as visualized by fluorescent microscopy using mpx:GFP114;mpeg:mCherry transgenic fish) in the overall fish as well as around the gut area than saponin-treated control-exposed larvae. Fewer macrophages were associated with a decreased expression of interleukin 22 (il22) in larvae exposed to saponin-treated OxyT-content compared to controls. Overall, this study shows that exposure to different microbial environments early in life might affect disease susceptibility of larval zebrafish.

摘要: Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes (conjugation and autogamy) that rely on their unique nuclear dimorphism, i.e., the presence of both a germline micronucleus (MIC) and a somatic macronucleus (MAC) in a single cell. The sexual processes show a high diversity in different ciliates. To better understand the differentiation and evolution of sexual processes in closely related species, we investigated the nuclear events during conjugation in Paramecium jenningsi strain GZ, a poorly studied close relative of the well-known P. aurelia complex. The main results include: (1) the conjugation process takes about 48 h, including three prezygotic divisions (meiosis I, II, and mitosis) and three postzygotic divisions; (2) the MICs are dominated by the parachute phase at the prophase of meiosis I; (3) after meiosis II, a variable number of nuclei undergo the third prezygotic division, and the two products near the paroral cone become the genetically identical migratory and stationary pronuclei; (4) the synkaryon divides three times to form the MIC and the MAC anlagen, but only one nuclear product of the first postzygotic division completes the next two divisions; and (5) an extra cell division is required to complete the last step of conjugation, during which two MIC anlagen undergo mitotic division while two MAC anlagen are distributed between the daughter cells without division. The com-parison of the nuclear events during conjugation in representatives of the class Oligohymenophorea reveals that usually there are three prezygotic divisions and a variable number of postzygotic divisions. However, the number of selected and differentiated nuclei after each division differs among species. This study provided a new model ciliate for further investigations of nuclear selection and differentiation as well as nuclear morphology during meiosis.