Screening of cadmium-responsive genes in Arabidopsis thaliana

Seedlings of Arabidopsis thaliana were treated with Cd, and transcript populations that changed their levels were screened by a fluorescent differential display method. Among the 170 cDNAs initially identified, 31 were further characterized for their identity, expression profile and response to other stresses. Sequencing revealed 10, 12 and 15 to be related to signal transduction, protein denaturing stress and responses to active oxygen species, respectively. Many of these genes responded not only to Cd, but also to oxidative stress, Cu ions and a protein denaturation agent. Upon introduction into yeast cells, two genes, encoding ATMEKK1 and a putative farnesylated protein that has two metal binding motifs, endowed marked toleration of Cd toxicity. These results suggest that oxidative stress and protein denaturation are important components of Cd toxicity, and that to cope with such stresses, plants activate a set of genes involved in metal detoxification, protein refolding and wound healing. The results also suggested temporarily and spatially well-regulated protein phosphorylation and activation of transcription factors, accompanied by their transcription.