Plant regeneration of the arsenic hyperaccumulator Pteris vittata L. from spores and identification of its tolerance and accumulation of arsenic and copper

An in vitro plant regeneration system was established from the spores of Pteris vittata and identification of its tolerance, and accumulation of gametophytes and callous, to arsenic (As) and copper (Cu) was investigated. The highest frequency (100%) of callus formation was achieved from gametophyte explants treated with 0.5 mg l(-1) 6-benzylaminopurine (6-BA) + 0.5 mg l(-1) gibberellin acid (GA). Furthermore, sporophytes were differentiated from the callus tissue derived from gametophyte explants on MS medium supplemented with 0.5 mg l(-1) 6-BA, 0.5-1.0 mg l(-1) GA and additional 300 mg l(-1) lactalbumin hydrolysate (LH) for 4 weeks. The optimum combination of 1/2 MS + 1.0 mg l(-1) GA + 0.5 mg l(-1) 6-BA + 300 mg l(-1) LH promoted sporophyte formation on 75 +/- 10% of the callus. Every callus derived from gametophyte explants could achieve 3-4 sporophytes. The in vitro growth of gametophyte and callus was accelerated in the medium containing Na3AsO4 lower than 0.5 mM, but this growth was inhibited with 2 mM Na3AsO4. And with the increase of Na3AsO4 in the culture medium from 0 to 2 mM, the As accumulation in gametophytes and callus increased and achieved a level of 763.3 and 315.4 mg kg(-1), respectively. Gametophytes and calluses transplanted to culture medium, supplemented with different concentrations of CuSO4, are similar to those in Na3AsO4, and the Cu accumulation in gametophytes could achieve 7,940 mg kg(-1) when gametophytes were subcultured in medium containing 3 mM CuSO4. These results suggested that the high efficiency propagation system could be a useful and rapid means to identify other heavy metal tolerance and accumulation. Further, the regeneration ability of callus made it possible for genetic transformation of this fern.