Isolation and genetic analysis of Chlamydomonas reinhardtii strains resistant to cadmium

Abstract

In Chlamydomonas reinhardtii, cadmium induces reduction of growth, reduction of chlorophyll content, and lethality. The toxicity was higher in a cell wall-deficient strains than in the wild type. By growing the cells on agar medium containing cadmium at concentrations inducing high lethality, stable resistant clones were isolated. The resistance was due to a nuclear mutation (cadA(R)) which probably preexisted in the wild-type cell population, as suggested by the fluctuation test. A double mutant (cadA(R) cadB(R)) was selected on media containing higher concentrations of cadmium. The cadB(R) mutation, which is unlikely to cadA(R), determines a resistance intermediate between the CadA(R) mutant and the wild-type strain. Both cadA(R) and cadB(R) mutations are partially dominant.