A CADMIUM-SENSITIVE, GLUTATHIONE-DEFICIENT MUTANT OF ARABIDOPSIS-THALIANA

The roots of the cadmium-sensitive mutant of Arabidopsis thaliana, cad 1-1, become brown in the presence of cadmium. A new cadmium-sensitive mutant affected at a second locus, cad2, has been identified using thi s phenotype. Genetic analysis has shown that the sensitive phenotype i s recessive to the wild type and segregates as a single Mendelian locu s. Assays of cadmium accumulation by intact plants indicated that the mutant is deficient in its ability to sequester cadmium. Undifferentia ted callus tissue was also cadmium sensitive, suggesting that the muta nt phenotype is expressed at the cellular level. The revel of cadmium- binding complexes formed in vivo was decreased compared with the wild type and accumulation of phytochelatins was about 10% of that in the w ild type. The level of glutathione, the substrate for phytochelatin bi osynthesis, in tissues of the mutant was decreased to about 15 to 30% of that in the wild type. Thus, the deficiency in phytochelatin biosyn thesis can be explained by a deficiency in glutathione.