Role of benzophenone-3 additive in chronic toxicity of polyethylene microplastic fragments to Daphnia magna.

Plastic additives may accelerate adverse effects of microplastics (MPs). This study aimed to identify the role of benzophenone-3 (BP-3) additive (10.82 ± 1.20% w/w) in chronic toxicity of polyethylene MP fragments to Daphnia magna (D. magna). MP fragments with and without BP-3 (48.37 ± 6.26 and 44.39 ± 11.16 µm, respectively) were synthesized and 4 d-old D. magna were exposed for 17 d. Daphnids exposed to MP/BP-3 fragments (98%) showed higher survival than those exposed to MP fragments (62%), which can be explained by a significantly low (p < 0.0001) bioconcentration of MP/BP-3 fragments. BP-3 leachate induced significantly low (p < 0.05) phototactic behavior of D. magna, likely leading to the low bioconcentration of MP/BP-3 fragments. Unlike MP fragments, both MP/BP-3 fragments and BP-3 additive inhibited embryonic development and offspring growth in a similar manner. Additionally, only BP-3 additive significantly induced (p < 0.05) higher lipid peroxidation in D. magna. This study suggests the critical role of plastic additives in MPs chronic toxicity to aquatic organisms, which should be further identified for other environmentally relevant plastic additives.

Size-dependent chronic toxicity of fragmented polyethylene microplastics to Daphnia magna.

Fragmented microplastics (MPs) are emerging contaminants in freshwater environments; however, long-term assessment of their toxicity remains limited. This study aimed to evaluate and compare the chronic toxicity (21 d) of synthesized polyethylene MP fragments and commercial polyethylene MP beads to Daphnia magna. Ingestion of small- and large-sized MP fragments (17.23 ± 3.43 and 34.43 ± 13.09 µm, respectively) by D. magna was significantly (p < 0.05) higher, by 8.3 and 5.2 times, respectively, than that of MP beads (39.54 ± 9.74 µm). The survival of D. magna exposed to small- and large-sized MP fragments (20 and 60%, respectively) was significantly (p < 0.05) lower than that of individuals exposed to MP beads (90%). In particular, small-sized MP fragments significantly (p < 0.05) reduced algal feeding (from 95% to 76%), body length (from 4.20 mm to 3.98 mm), and the number of offspring (from 109 to 74) in D. magna, when compared with MP beads, likely due to their longer retention time and greater interference in the digestive tract. These findings suggest that fragmentation of MPs into µm-scale particles can pose a significant ecological risk to aquatic organisms; moreover, further studies are required to identify the underlying toxicity mechanism.

Expression of Camelina WRINKLED1 Isoforms Rescue the Seed Phenotype of the Arabidopsis wri1 Mutant and Increase the Triacylglycerol Content in Tobacco Leaves.

Triacylglycerol (TAG) is an energy-rich reserve in plant seeds that is composed of glycerol esters with three fatty acids. Since TAG can be used as a feedstock for the production of biofuels and bio-chemicals, producing TAGs in vegetative tissue is an alternative way of meeting the increasing demand for its usage. The WRINKLED1 (WRI1) gene is a well-established key transcriptional regulator involved in the upregulation of fatty acid biosynthesis in developing seeds. WRI1s from Arabidopsis and several other crops have been previously employed for increasing TAGs in seed and vegetative tissues. In the present study, we first identified three functional CsWRI1 genes (CsWRI1A. B, and C) from the Camelina oil crop and tested their ability to induce TAG synthesis in leaves. The amino acid sequences of CsWRI1s exhibited more than 90% identity with those of Arabidopsis WRI1. The transcript levels of the three CsWRI1 genes showed higher expression levels in developing seeds than in vegetative and floral tissues. When the CsWRI1A. B, or C was introduced into Arabidopsis wri1-3 loss-of-function mutant, the fatty acid content was restored to near wild-type levels and percentages of the wrinkled seeds were remarkably reduced in the transgenic lines relative to wri1-3 mutant line. In addition, the fluorescent signals of the enhanced yellow fluorescent protein (eYFP) fused to the CsWRI1 genes were observed in the nuclei of Nicotiana benthamiana leaf epidermal cells. Nile red staining indicated that the transient expression of CsWRI1A. B, or C caused an enhanced accumulation of oil bodies in N. benthamiana leaves. The levels of TAGs was higher by approximately 2.5- to 4.0-fold in N. benthamiana fresh leaves expressing CsWRI1 genes than in the control leaves. These results suggest that the three Camelina WRI1s can be used as key transcriptional regulators to increase fatty acids in biomass.