Characterization of Arsenate Reductase in the Extract of Roots and Fronds of Chinese Brake Fern, an Arsenic Hyperaccumulator

Abstract

Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.

First evidence on different transportation modes of arsenic and phosphorus in arsenic hyperaccumulator Pteris vittata

“…It is only in non-hyperaccumulating plants, such as Holcus lanatus L. and Lemna gibba, that As has been confirmed to be taken up via a P translocation system (Meharg and Macnair, 1992;Ullrich-Eberius et al, 1989). In As-hyperaccumulating P. vittata, there has been no direct evidence on the cotransporter for the analogs As and P. In addition, As(V) is mostly reduced to As(III) (not a P analog) in P. vittata rhizoids, which is the main As form transported to aboveground parts, and this reduction process is regarded as an important process distinguishing an As hyperaccumulator from a non-hyperaccumulator (Duan et al, 2005;Huang et al, 2004). Therefore, it would be interesting to study the interaction of As and P, before and after the reduction of As(V) to As(III) in P. vittata rhizoids, from a more microscopic and dynamic perspective.…”

Photoinitiated Polymerization: Advances, Challenges, and Opportunities

“…The limitations associated with the non-nucleophilic counterion of onium compounds, especially SbF 6 -and AsF 6 -, include high toxicity and high cost because of their central heavy metals. It was reported 227,228 that long-term exposure of these metal salts to human skin led to increased incidences of various cancers. Furthermore, the preparation of such initiators from their corresponding onium salts with halides requires additional steps, i.e., counteranion exchange; thus, this makes them expensive.…”

Multivariate analysis of elements in chinese brake fern as determined using neutron activation analysis

“…However, routine analysis of As with NAA for the determination of As contamination or screening for As hyperaccumulators is invalid. Numerous studies have confirmed the As-hyperaccumulation property of the Chinese brake fern; however, little is known about the correlation between As and other elements in this fern (2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Two experiments reported that K increased and Ca decreased in the fronds of the Chinese brake fern when As was added to the pots (25,26).…”

“…The fern has great ability for tolerance and accumulation of As; it can accumulate more than 1000 mg/kg As in its fronds when growing on the tailings with 23,400 mg/kg As in the field and soils spiked with 1500 mg/kg As in greenhouse conditions (5,6). A growing interest has been focused on the mechanisms of As uptake and accumulation by this fern; however, much has been left unresolved (7)(8)(9)(10)(11).…”