Mechanisms of arsenic hyperaccumulation in Pteris species: root As influx and translocation

• Published in: Planta Vol. 219; no. 6; pp. 1080 - 1088
• Main Authors: Poynton, C.Y, Huang, J.W, Blaylock, M.J, Kochian, L.V, Elless, M.P
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.10.2004; Springer; Springer Nature B.V
• Subjects: Agronomy. Soil science and plant productions; Arsenates; Arsenic; Arsenic - metabolism; Arsenites; Biological and medical sciences; Biological Transport; Economic plant physiology; Ferns; Fundamental and applied biological sciences. Psychology; Hyperaccumulators; Kinetics; Nephrolepis exaltata; Phosphates; Phosphates - metabolism; physiological transport; Plant roots; Plant Roots - metabolism; Plant Shoots - metabolism; Plants; Pteris - metabolism; Pteris cretica; Pteris vittata; quantitative analysis; Radioisotopes; Roots; Speciation; Species Specificity; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Time Factors; toxic substances; Translocation; uptake mechanisms; Translocation; Root; Plant leaf; Pteridophyta; Pteris; Phytoremediation; Membrane transport; Arsenate; Phosphate; Above ground plant part; Kinetics; Arsenite; Filicineae
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-004-1304-8

Several species of fern from the Pteris genus are able to accumulate extremely high concentrations of arsenic (As) in the fronds. We have conducted short-term unidirectional As influx and translocation experiments with 73As-radiolabeled arsenate, and found that the concentration-dependent influx of arsenate into roots was significantly larger in two of these As-hyperaccumulating species, Pteris vittata (L.) and Pteris cretica cv. Mayii (L.), than in Nephrolepis exaltata (L.), a non-accumulating fern. The arsenate influx could be described by Michaelis-Menten kinetics and the kinetic parameter K(m) was found to be lower in the Pteris species, indicating higher affinity of the transport protein for arsenate. Quantitative analysis of kinetic parameters showed that phosphate inhibited arsenate influx in a directly competitive manner, consistent with the hypothesis that arsenate enters plant roots on a phosphate-transport protein. The significantly augmented translocation of arsenic to the shoots that was seen in these As hyperaccumulator species is proposed to be due to a combination of the increased root influx and also decreased sequestration of As in the roots, as a larger fraction of As could be extracted from roots of the Pteris species than from roots of N. exaltata. This leaves a larger pool of mobile As available for translocation to the shoot, probably predominantly as arsenite.