Organophosphate diesters (DAPs) and hydroxylated organophosphate flame retardants (HO-OPFRs) as biomarkers of OPFR contamination in a typical freshwater food chain.

Organophosphate flame retardants (OPFRs) can rapidly biotransform into two types of metabolites in biota: (1) organophosphate diesters (DAPs) and (2) hydroxylated OPFRs (HO-OPFRs). Therefore, the levels of parent OPFRs alone are not sufficient to indicate OPFR pollution in biological organisms. This study analyzed 12 OPFR metabolites, including 6 DAPs and 6 HO-OPFRs, in a typical freshwater food chain consisted of crucian carp, catfish, mud carp, snakehead, and oriental river prawn. The total concentrations of OPFR metabolites were comparable to those of parent OPFRs, and ranged from 0.65 to 17 ng/g ww. Bis(2-butoxyethyl) 3'-hydroxy-2-butoxyethyl phosphate (14%-77%), di-n-butyl phosphate (DNBP) (6.7%-24%), bis(1-chloro-2-propyl) phosphate (BCIPP) (0.7%-35%), and 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) (6.0%-24%) were the major OPFR metabolites. Various aquatic species exhibited significant differences in their OPFR metabolite/parent ratios (MPR) (p < 0.05), indicating varying biotransformation potentials of different organisms for various OPFRs. The growth-independent accumulation of tri-n-butyl phosphate (TNBP), tris(chloro-2-propyl) phosphate (TCIPP), triphenyl phosphate, and 2-ethylhexyl diphenyl phosphate in mud carps could be explained by their biotransformation potential. A significant negative correlation was found between the concentration of bis(2-butoxyethyl) phosphate and δ15N values (p < 0.05), with a calculated trophic magnification factor (TMF) of 0.66. Significant positive correlations were observed between BCIPP and TCIPP (R2 = 0.25, p < 0.05), as well as between DNBP and TNBP (R2 = 0.30, p < 0.01), implying that these two DAPs could be used as biomarkers to quantitatively assess TCIPP and TNBP contamination in wild aquatic organisms.

Identification of Respiratory Burst Oxidase Homolog (Rboh) Family Genes From Pyropia yezoensis and Their Correlation With Archeospore Release.

Reactive oxygen species (ROS) play important regulatory roles in plant growth and development, as well as in cell differentiation and stress responses. Respiratory burst oxidase homolog (RBOH) is the key enzyme in ROS production. So far, the Rboh family genes in Pyropia yezoensis have not been comprehensively characterized, and whether their function was involved in the formation of archeospores is still unknown. In this study, a total of 11 PyRboh genes were identified from the P. yezoensis genome by homology mining. Through phylogenetic analysis, it is suggested that the PyRboh genes were evolutionarily conserved among the lineages of red algae, but a few genes exhibited a species-specific manner. The treatment of P. yezoensis blades with NADPH oxidase inhibitor diphenylene iodonium (DPI) could significantly inhibit the formation of archeospores, suggesting that RBOH may be involved in the formation of archeospores. According to PyRboh gene expression analysis using the P. yezoensis strains with obvious differences in releasing archeospores, it is showed that the expression trends of most genes were consistent, with no significant difference between strains, whereas the expression pattern of the two P. yezoensis-specific genes (PyRbohJ and PyRbohK) was positively correlated with the amount of archeospores. Furthermore, as treatment of blades with allantoin resulted in a significant increase in the release of archeospores, the expression levels of PyRbohJ and PyRbohK were also consistently upregulated, further confirming the relationship between the two genes and archeospore formation. These findings provide insights into the molecular mechanism of P. yezoensis archeospore formation.