CHARACTERIZATION OF ARABIDOPSIS-THALIANA CDNAS THAT RENDER YEASTS TOLERANT TOWARD THE THIOL-OXIDIZING DRUG DIAMIDE

Diamide oxidizes cellular thiols and induces oxidative stress, To isol ate plant genes which may, when overexpressed, increase tolerance of p lants toward oxidative damage, an in vivo diamide tolerance screening in yeasts,cas used, An Arabidopsis cDNA library in a yeast expression vector was used to transform a yeast strain with intact antioxidant de fense, Cells from approximate to 10(5) primary transformants were sele cted for resistance to diamide, Three Arabidopsis cDNAs which confer d iamide tolerance were isolated, This drug tolerance was specific and n o cross tolerance toward hydroperoxides was found, One cDNA (D3) encod es a polypeptide which has an amino-terminal J domain characteristic o f a divergent family of DnaJ chaperones, Another (D18) encodes a putat ive dTDP-D-glucose 4,6-dehydratase. Surprisingly, the third cDNA (D22) encodes a plant homolog of gamma-glutamyltransferases. It would have been difficult to predict that the expression of those genes would lea d to an improved survival under conditions of depletion of cellular th iols, Hence, we suggest that this cloning approach may be a useful con tribution to the isolation of plant genes that can help to cope with o xidative stress.