Integrating Transcriptome and Metabolome Analyses Revealed Salinity Induces Arsenobetaine Biosynthesis in Marine Medaka (Oryzias melastigma).

Marine fish exhibit elevated levels of arsenobetaine (AsB), while the impact and underlying mechanism of salinity on AsB biosynthesis remain inadequately explored. In this study, marine medaka (Oryzias melastigma), typically inhabiting 30‰ high salinity, were gradually acclimated to low salinities of 20, 10, and 0‰. Following acclimation, the fish were exposed to arsenate (As(V)) in their diet for 30 days. Results showed a significant accumulation of total arsenic (As) and AsB concentrations in the muscle and head tissues of the exposed fish, with these accumulations exhibiting a positive correlation with water salinity. Transcriptome analyses revealed that exposure to As(V) at low salinity may disrupt membrane components and induce cytoskeletal injuries, while at high salinity, it triggered oxidoreductase activity and transmembrane transport. Metabolome analyses indicated that low salinity induced osmotic stress, resulting in an increased requirement for amino acids to upload intracellular osmotic equilibrium in O. melastigma. Furthermore, the key organic osmolytes and amino acids, including taurine, l-methionine, guanidinoethyl sulfonate, and N-acetyl-l-aspartic acid, exhibited a negative correlation with the AsB concentration. These findings indicated that salinity can regulate osmotic balance by influencing amino acid synthesis under low salinity and stimulating AsB synthesis under high salinity conditions in O. melastigma. This study provides insights into the impact of high salinity on AsB biosynthesis, the underlying regulatory mechanisms, and implications for managing As(V) risk.

Shape-dependent adsorption of CeO2 nanostructures for superior organic dye removal.

Highly efficient removal of dye pollutants from water resources remains a great challenge. Herein, we demonstrate a new approach for the efficient removal of anionic organic dyes from wastewater using shape-dependent CeO2 nanostructures. It was found that the volume stoichiometry ratio of ethanol to water (EtOH/H2O) was a key factor affecting the CeO2 nanostructures. Accordingly, the adsorption capacity of the spindle CeO2 nanostructure for Congo red reached 162.4 mg g-1, which is much higher than that of octahedral and spherical CeO2 or other adsorbents previously reported. The superior adsorption performance may be mainly attributed to the peculiar structure and presence of electrostatic interactions between the sample surface and dye molecules. This finding will provide new avenues for using promising adsorbent materials for dye removal in water treatments.