Characterization of Arsenic Biotransformation by a Typical Bryophyte Physcomitrella patens.

Arsenic (As) is a ubiquitous environmental toxin that has created catastrophic human health and environmental problems around world. Physcomitrella patens is a potential model plant for the study of environmental monitoring, which exists in all kinds of ecosystems. In this study, arsenic metabolism was investigated by this moss. When supplied with different levels of arsenate (50, 100, 200 µmol/L) for a 4-week period, the total arsenic concentrations were up to 231.4-565.4 mg/kg DW in this moss. Arsenite concentration increased with increasing external arsenate concentrations, the proportion was up to 25.1-36.8% of the total As. An arsenate reductase, PpACR2, was identified and functionally characterized. Heterologous expression of PpACR2 in an As(V)-sensitive strain WC3110 (ΔarsC) of Escherichia coli conferred As(V) resistance. Purified PpACR2 protein exhibited the arsenate reductase activity. Given its powerful As accumulation ability, the bryophyte could be exploited in bioremediation of As-contaminated environments.