Induction of phytochelatin (class III metallothionein) and incorporation of copper in transformed hairy roots of Rubia tinctorum exposed to cadmium

Hairy roots of Rubia tinctorum L. were cultured in Murashige-Skoog liquid medium containing cadmium (Cd) chloride (100 mu mol/L), and the induction of phytochelatin including desglycyl type (PC) was studied using a high performance liquid chromatograph connected with an inductively coupled plasma-atomic emission spectrometer. The total Cd concentration in the hairy roots was kept almost constant from days 1 to 14 during Cd exposure, but the portion that was recovered from the supernatant fraction increased with time. The increase reflected the induction of Cd-binding PC. The PC also contained copper as a metal constituent. When the metal composition in PC induced by Cd was compared in the hairy roots and the normal root cultures of R. tinctorum, the latter showed a notably higher Cu/Cd ratio, mainly due to a lower Cd level.