Glutathione-S-transferase in Nereis succinea (Polychaeta) and its induction by xeno-estrogen

RNA-Seq Analyses of Midgut and Fat Body Tissues Reveal the Molecular Mechanism Underlying Spodoptera litura Resistance to Tomatine

Plants produce secondary metabolites to provide chemical defense against herbivorous insects, whereas insects can induce the expression of detoxification metabolism-related unigenes in counter defense to plant xenobiotics. Tomatine is an important secondary metabolite in tomato (Lycopersicon esculentum L.) that can protect the plant from bacteria and insects. However, the mechanism underlying the adaptation of Spodoptera litura, a major tomato pest, to tomatine in tomato is largely unclear. In this study, we first found that the levels of tomatine in tomatoes subjected to S. litura treatment were significantly increased. Second, we confirmed the inhibitory effect of tomatine on S. litura by adding moderate amounts of commercial tomatine to an artificial diet. Then, we utilized RNA-Seq to compare the differentially expressed genes (DEGs) in the midgut and fat body tissues of S. litura exposed to an artificial diet supplemented with tomatine. In total, upon exposure to tomatine, 134 and 666 genes were upregulated in the S. litura midgut and fat body, respectively. These DEGs comprise a significant number of detoxification-related genes, including 7 P450 family genes, 8 glutathione S-transferases (GSTs) genes, 6 ABC transport enzyme genes, 9 UDP-glucosyltransferases genes and 3 carboxylesterases genes. Moreover, KEGG analysis demonstrated that the upregulated genes were enriched in xenobiotic metabolism by cytochrome P450s, ABC transporters and drug metabolism by other enzymes. Furthermore, as numerous GSTs were induced by tomatine in S. litura, we chose one gene, namely GSTS1, to confirm the detoxification function on tomatine. Expression profiling revealed that GSTS1 transcripts were mainly expressed in larvae, and the levels were the highest in the midgut. Finally, when larvae were injected with double-stranded RNA specific to GSTS1, the transcript levels in the midgut and fat body decreased, and the negative effect of the plant xenobiotic tomatine on larval growth was magnified. These results preliminarily clarified the molecular mechanism underlying the resistance of S. litura to tomatine, establishing a foundation for subsequent pest control.

Long-term exposure to caffeine and carbamazepine: Impacts on the regenerative capacity of the polychaete Diopatra neapolitana

The toxicity induced in non-target organisms by pharmaceutical drugs has been the focus of several studies. In the aquatic environment, most of the studies have been devoted to fish and bivalves, while little is known on the impacts induced in polychaetes. The present study evaluated the impacts of carbamazepine and caffeine on the regenerative capacity of Diopatra neapolitana, a polychaete species with high ecological and economic relevance. Under laboratory controlled conditions polychaetes were exposed, during 28 days, to carbamazepine (Ctl-0.0; 0.3; 3.0; 6.0; 9.0 μg/L) and caffeine (Ctl-0.0; 0.5; 3.0; 18.0 μg/L). During the experiment, at days 11, 18, 25, 32, 39 and 46 after amputation, for each specimen, the percentage of the body width regenerated was determined and the number of new segments was counted. The regenerative capacity was assessed considering the number of days needed to achieve full regeneration and the total number of new segments. The obtained results revealed that with the increase of drugs concentrations organisms regenerated less new segments and took longer to completely regenerate.

Preliminary evaluation of Diopatra neapolitana regenerative capacity as a biomarker for paracetamol exposure

An increasing number of studies established unequivocal relationships between exposure to pharmaceutical drugs and toxicity in wildlife. However, few studies investigated physiological alterations caused by such compounds in polychaetes. Thus, in this study, the effects of increasing concentrations of paracetamol were studied in the polychaete Diopatra neapolitana using tissue regenerative capacity as a biomarker. The obtained results revealed that individuals exposed to ecologically relevant concentrations (namely, 25 μg/L) of paracetamol exhibited significantly lower capacity to regenerate their body in comparison with control organisms. This study evidenced that paracetamol can induce significant physiological alterations in D. neapolitana resulting in an overall diminished regenerative capacity, which is of significance to a species with high ecological and economic relevance. Additionally, this study indicates the promise of D. neapolitana as a test organism in laboratory-based bioassays, but also as an adequate sentinel species to pharmaceutical drugs.

17β-Estradiol induces supernumerary primordial germ cells in embryos of the polychaete Platynereis dumerilii

In the polychaete Platynereis dumerilii exactly four primordial germ cells (PGCs) arise in early development and are subject to a transient mitotic arrest until the animals enter gametogenesis. In order to unravel the mechanisms controlling the number of PGCs in Platynereis, we tested whether the steroid 17β-estradiol (E2) is able to induce PGC proliferation, as it had been described in other species. Our data provide strong support for such a mechanism, showing that E2 significantly increases the occurrence of larvae with supernumerary PGCs in Platynereis in a dose dependent manner. E2 responsiveness is restricted to early developmental stages, when the PGCs are specified. During these stages, embryos exhibit high expression levels of the estradiol receptor (ER). The ER transcript localizes to the yolk-free cytoplasm of unfertilized eggs and segregates into the micromeres during cleavage stages. Nuclear ER protein is found asymmetrically distributed between daughter cells. Neither transcript nor protein is detectable in PGCs at larval stages. Addition of the specific estradiol receptor inhibitor ICI-182,780 (ICI) abolishes the proliferative effect of E2, suggesting that it is mediated by ER signaling. Our study reports for the first time an ER mediated proliferative effect of E2 on PGCs in an invertebrate organism.

Development and maturation in the nereidid polychaetes Platynereis dumerilii and Nereis succinea exposed to xenoestrogens

Few studies link biochemical, cellular and whole animal effects of toxic compounds with growth and reproductive output on invertebrate model organisms. Thus, we explore the effects of xenoestrogens on nereid worms. Larvae of Platynereis dumerilii exposed to estradiol (E(2)) ethynylestradiol (EE(2)) and nonyplhenol (NP) observing the effects on growth, primordial germ cell (PGC) proliferation and maturation. In addition, a single exposure study was performed with a 50 days latency period on adult worms of Nereis succinea. Since reduced glutathione (GSH) is required in detoxification of NP and is the precursor of the spawning pheromone nereithione (CSSG) in N. succinea, we analysed how the estrogenic chemical NP affects GSH concentrations. PGC were not affected by exposure to E(2) and EE(2) from 24hpf to 6 days. Chronic exposure of P. dumerilii with NP over the full life cycle did not influence segment proliferation. Mature females that developed, even at high concentrations, were able to spawn and successful fertilization occurred. However, at high NP levels no P. dumerilii males matured. A significant decline of GSH can be seen in N. succinea males upon treatment with NP, but not in females, indicating that females stabilize GSH levels even in stress situations. This study shows some results that link the foundation to causally integrate toxic exposure to xenoestrogens with development, growth and reproductive outputs in nereidid polychaetes.