Abstract
Callus of a metal hypertolerant fern, Athyrium yokoscense (Ay), was exposed to 100 μM of Cd, and the molecular/physiological responses were compared to those in callus of Nicotiana tabacum (Nt). Ay could grow without any visible damage by the Cd exposure, while Nt reduced the growth severely. At that time, Ay and Nt differently accumulated Cd in cell wall fraction (about 90% and 40%,respectively), although each total cellular Cd content was almost the same. The Cd exposure reduced only Fe concentration in Nt. Phytochelatin synthase gene (PCS) expressions and the synthesis of phytochelatins, which plays a major role in Cd detoxification among common plant species, were stable even after the Cd exposure in Ay, while both of these increased significantly in Nt. These results suggest that the Cd tolerance of Ay is based on a phytochelatin-independent Cd-exclusion from inner cells and a preferential uptake of essential metals.
