Development of a bioassay for engineered nanoparticles (ENPs) in the environment

As the global production and use of the nanoparticles increases, it is certain that the engineered nanoparticles will be released into the environment. However, their effects on the humans, other organisms, and ecosystems are still unknown. In order to understand the potential toxicity and bioavailable concentration of the metal-based engineered nanoparticles or toxic trace metals in the environment, Chlamydomonas rehardtii was utilized as a study model to construct the bioassay. Although C. reinhardtii primarily serves as a model organism in biology research, the prevalent reporter genes such as GFP or luciferase are poorly expressed in this organism. No efficient bioluminescent or biofluorescent reporters are available for constructing our bioassay, thus, an endogenous gene, the CRLpcr-1 gene which encodes protochlorophyllide oxidoreductase, as a reporter gene was first evaluated and expected to be served as a useful and robust reporter gene in C. reinhardtii. The 4.9 kb transgene including the nickel inducible promoter, the Cyc6 promoter, the reporter gene, the CRLpcr-1 gene, and the selectable marker was assembled using homologous recombination in Saccharomyces cerevisiae. The results showed that C. reinhardtii failed to express the CRLpcr-1 transgene probably due to the transcriptional gene silencing mechanism. In future, a new strain that is defective in transcriptional silencing which is genetic crossed with a new mutant strain (pc1, y7, cw15, arg7) with flagella could be employed to construct our bioassay