Cells react to oxidative stress conditions by launching a defense response through the induction of nuclear gene expression. The advent of microarray technologies allowed monitoring of oxidative stress-dependent changes of transcript levels at a comprehensive and genome-wide scale, resulting in a series of inventories of differentially expressed genes in different organisms. We performed a meta-analysis on hydrogen peroxide (H(2)O(2))-induced gene expression in the cyanobacterium Synechocystis PCC 6803, the yeast Saccharomyces cerevisiae and Schizosaccharomyces pombe, the land plant Arabidopsis thaliana, and the human HeLa cell line. The H(2)O(2)-induced gene expression in both yeast species was highly conserved and more similar to the A. thaliana response than that of the human cell line. Based on the expression characteristics of genuine antioxidant genes, we show that the antioxidant capacity of microorganisms and higher eukaryotes is differentially regulated. Four families of evolutionarily conserved eukaryotic proteins could be identified that were H(2)O(2) responsive across kingdoms: DNAJ domain-containing heat shock proteins, small guanine triphosphate-binding proteins, Ca(2+)-dependent protein kinases, and ubiquitin-conjugating enzymes.