Abstract
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 (H2O2) initiate signaling events, resulting in the attenuation of Fe acquisition through the inhibition of FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT). As this H2O2 increase occurs in a FIT-dependent manner, our aim was to understand the processes involved in maintaining H2O2 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 H2O2 levels in roots. Analysis of the Fe homeostasis transcription cascade revealed that H2O2 influences the gene expression of downstream regulators FIT, BHLH genes of group Ib, and POPEYE (PYE); however, H2O2 did not affect their upstream regulators, such as BHLH104 and ILR3. Our data shows that FIT and CAT2 participate in a regulatory loop between H2O2 and prolonged Fe deficiency.
Highlights
Plants are constantly confronted with a varying array of stress conditions to which they need to respond and adapt in order to survive
Our gene expression analysis revealed CAT2 as a potential FITdependent regulator of H2O2 levels under prolonged Fe deficiency.To understand how CAT2 participates in the regulation of Fe deficiency responses, we investigated the Fe response in the previously characterized CAT2 loss-of-function mutant cat2-1 (Bueso et al, 2007; Queval et al, 2007)
Among reactive oxygen species (ROS), H2O2 is directly involved in the regulation of responses to prolonged Fe deficiency through promoting the expression of the transcription factor ZINC FINGER OF ARABIDOPSIS THALIANA12 (ZAT12) and regulating its stability (Brumbarova et al, 2016b; Le et al, 2016)
Summary
Plants are constantly confronted with a varying array of stress conditions to which they need to respond and adapt in order to survive Aerobic metabolic processes, such as photosynthesis and respiration, as well as chemical reactions in the cell, lead to the production of reactive oxygen species (ROS), the most prominent of them being superoxide (O2 ̇ −), hydrogen peroxide (H2O2), hydroxyl radical (OH·), and singlet oxygen (1O2). ROS can be produced in different cellular compartments and have different reactivity and stability They can increase in amount under stress conditions and damage proteins, nucleic acids, and lipids, eventually triggering cell death. Arabidopsis thaliana (Arabidopsis) has three catalase genes, CAT1, CAT2, and CAT3, whose products dismutate H2O2 to H2O and O2, with varying contributions of the three proteins in the different plant organs (Mhamdi et al, 2010). CAT loss-offunction mutants have been successfully employed as a model system to study the role of ROS in abiotic and biotic stress responses (Mhamdi et al, 2010; Sewelam et al, 2014; Schmidt et al, 2020)
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