Reactive oxygen species coordinate the transcriptional responses to iron availability in Arabidopsis

Reactive oxygen species play a central role in the regulation of plant responses to environmental stress. Under prolonged iron (Fe) deficiency, increased levels of hydrogen peroxide (H(2)O(2)) initiate signaling events, resulting in the attenuation of Fe acquisition through the inhibition of FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT). As this H(2)O(2) increase occurs in a FIT-dependent manner, our aim was to understand the processes involved in maintaining H(2)O(2) levels under prolonged Fe deficiency and the role of FIT. We identified the CAT2 gene, encoding one of the three Arabidopsis catalase isoforms, as regulated by FIT. CAT2 loss-of-function plants displayed severe susceptibility to Fe deficiency and greatly increased H(2)O(2) levels in roots. Analysis of the Fe homeostasis transcription cascade revealed that H(2)O(2) influences the gene expression of downstream regulators FIT, BHLH genes of group Ib, and POPEYE (PYE); however, H(2)O(2) did not affect their upstream regulators, such as BHLH104 and ILR3. Our data shows that FIT and CAT2 participate in a regulatory loop between H(2)O(2) and prolonged Fe deficiency.