Hydrogen peroxide is a major regulator of plant programmed cell death (PCD) but little is known about the downstream genes from the H(2)O(2)-signaling network that mediate the cell death. To address this question, a novel system for studying H(2)O(2)-induced programmed cell death in Arabidopsis thaliana was used. The catalase inhibitor aminotriazole (AT) reduced the catalase activity and caused endogenous accumulation of hydrogen peroxide that eventually triggered cell death. Microarray analysis with a DNA chip representing 21500 genes and subsequent comparison with other PCD-related expression studies revealed a set of new H(2)O(2)-responsive genes that were highly regulated in a common fashion during different types of PCD. These included an oxoglutarate-dependent dioxygenase and various oxidoreductases, the transcription factors Zat11, WRKY75 and NAM, proteasomal components, a heterologous group of genes with diverse functions, and genes encoding proteins with unknown functions. Knockout lines of the oxoglutarate-dependent dioxygenase exhibited significantly reduced death symptoms and chlorophyll loss upon H(2)O(2)-induced cell death, indicating a role for this gene in the cell death network.