Effects of an anti-WSSV transgenic cyanobacterial oral agent on the development, reproduction, and physiology of Daphnia magna

Trans- vp 28 gene cyanobacteria have good efficacy as an oral agent against shrimp white spot syndrome virus (WSSV) infection in shrimp and have promising applications. However, little research on the environmental safety of transgenic cyanobacteria has been published. Species of Cladocera, an order of aquatic arthropods commonly found in aquatic ecosystems, might be exposed to the VP28 protein released from VP28-transgenic cyanobacteria. In this study we cultured Daphnia magna in M4 medium (M4 medium was supplemented with trans-vp28 gene cyanobacteria named S-vp28 group, trans-empty vector cyanobacteria named S-pRL489 group, wild-type cyanobacteria named S-WT group, and Scenedesmus obliquus named G-group as control, respectively) to evaluate the impact of the cyanobacteria on the growth and development of D. magna . In the 21-day toxicology experiment, the results showed the morphology of D. magna showed no abnormalities. The mean number of eggs and the total number of eggs laid by D. magna were not significantly different in these groups. but the shedding time of D. magna in the cyanobacteria group was faster than that of D. magna in the control group. In the 7-day toxicology experiment, we measured the activities of acetylcholinesterase (AchE), catalase (CAT), glutathione S-transferase (GST), and gene transcription levels of D. magna . The results showed that there were no significant differences in AchE and CAT activities of D. magna in the three cyanobacteria groups. The GST activity of D. magna in the green algae group was significantly higher than that in the cyanobacteria groups. At the same time, there was no significant difference between the S-pRL489 group and the S-vp28 group. We found no significant correlation between enzyme activity levels and gene transcription levels in each group. This study indicates the Trans- vp 28 gene cyanobacteria did not adversely affect this non-target species.