A Biomonitoring System of Environmental Cadmium Exposure Based on Fluorescence-Tagged Fission Yeast

Objectives: Our previous studies have constructed SPBC776.03 Δ strain of Schizosaccharomyces pombe , and shown that deficiency of SPBC776.03 gene may lead to mototic chromosome missegrega-tion during cell cycle. This work aims to establish a biomoniting system based on fission yeast to assess the genotoxity and mutangenecity of environmental cadmium ions. Methods: Rad22-GFP DNA repair foci examination, articifical mini-chromosome loss test, and real-time quantitative PCR. Results: Using PCR-based techniques and homologous recombination, a yeast strain called Rad22-GFP was constructed as an indicator of environmental genotoxic agents, in which the DNA damge associated gene Rad22 was tagged with GFP in its chromosomal locus. Under Cd exposure, this indicator strain displayed multiple (>2) DNA repair foci, whereas none was observed with untreated control. As for the positive control strain SPBC776.03 Δ, multiple (>2) DNA repair foci were observed during cell cycle even in the absence of Cd stress. Real-time qPCR analyses have revealed that, SPBC776.03 transcriptional levels were found to downregulate by three-fold when exposed to Cd 2+ , in contrast to untreated wild-type counterparts, suggesting that SPBC776.03 would be a responsive gene of fission yeast to the Cd stress. Conclusions: Our studies have constructed a biomointoring system of envirommental cadmium exposure based on fluorescence-tagged Rad22 expression, Rad22-GFP, in fission yeast, which has advantages of speediness and convenience in the assessment of Cd toxicity.