Jr. Dominguez-solis et al., The cytosolic O-acetylserine(thiol)lyase gene is regulated by heavy metalsand can function in cadmium tolerance, J BIOL CHEM, 276(12), 2001, pp. 9297-9302
Regulation of the expression of the cytosolic O-acetyl-serine(thiol)lyase g
ene (Atcys-3A) from Arabidopsis thaliana under heavy metal stress condition
s has been investigated. Northern blot analysis of Atcys-3A expression show
s a 7-fold induction after 18 h of cadmium treatment. Addition of 50 muM Cd
Cl2 to the irrigation medium of mature Arabidopsis plants induces a rapid a
ccumulation of the mRNA throughout the leaf lamina, the root and stem corte
x, and stem vascular tissues when compared with untreated plants, as observ
ed by in situ hybridization. High pressure liquid chromatography analysis o
f GSH content shows a transient increase after 18 h of metal treatment. Our
results are compatible with a high cysteine biosynthesis rate under heavy
metal stress required for the synthesis of GSH and phytochelatins, which ar
e involved in the plant detoxification mechanism. Arabidopsis-transformed p
lants overexpressing the Atcys-3A gene by up to g-fold show increased toler
ance to cadmium when grown in medium containing 250 muM CdCl2, suggesting t
hat increased cysteine availability is responsible for cadmium tolerance. I
n agreement with these results, exogenous addition of cystine can, to some
extent, also favor the growth of wild type plants in cadmium-containing med
ium. Cadmium accumulates to higher levels in leaves of tolerant transformed
lines than in wild-type plants.