Ultraviolet-B acclimation is supported by functionally heterogeneous phenolic peroxidases
Arnold Rácz1, Gyula Czégény1, Kristóf Csepregi1
1Department of Plant Biology, Faculty of Sciences, University of Pécs, Ifjúság u. 6, Pecs, 7624, Hungary.
Scientific Reports
|October 2, 2020
Summary
UV-B radiation and hydrogen peroxide treatments increased hydrogen peroxide levels in tobacco leaves but affected antioxidant mechanisms differently. UV-B specifically activated certain enzymes, indicating a complex plant response to stress.
Area of Science:
- Plant Physiology
- Biochemistry
- Environmental Stress Response
Background:
- Hydrogen peroxide (H2O2) is a reactive oxygen species involved in plant signaling and stress responses.
- UV-B radiation can induce oxidative stress in plants, necessitating protective mechanisms.
- Understanding how plants neutralize H2O2 under different stress conditions is crucial for plant resilience.
Purpose of the Study:
- To investigate the distinct effects of UV-B radiation and hydrogen peroxide (H2O2) treatments on tobacco leaf physiology.
- To elucidate the differential impacts of these treatments on H2O2-scavenging mechanisms, including enzymatic and non-enzymatic pathways.
- To examine the substrate-dependent activity of class-III peroxidase (POD) in response to UV-B and H2O2.
Main Methods:
- Tobacco plants were subjected to supplementary UV-B radiation, H2O2 irrigation, or a combined treatment for four days.
- Leaf photosynthesis was assessed to determine treatment-induced damage.
- Levels of H2O2 and the activity of H2O2-neutralizing enzymes (specifically class-III peroxidase) were measured using various substrates.
Main Results:
- Neither UV-B nor H2O2 treatments alone or in combination damaged leaf photosynthesis.
- Both treatments elevated leaf H2O2 content, but UV-B primarily enhanced enzymatic antioxidant capacities, while H2O2 boosted non-enzymatic capacities.
- Class-III peroxidase (POD) activity showed substrate-dependent responses, with UV-B treatment leading to higher activity against natural phenolic substrates compared to an artificial substrate.
Conclusions:
- UV-B radiation and H2O2 trigger distinct H2O2-scavenging pathways in tobacco leaves.
- The observed substrate-dependent activity of POD suggests functional heterogeneity and selective isoform activation in UV-B acclimated leaves.
- Elevated H2O2 levels alone do not appear to be the sole trigger for the activation of specific POD isoforms under UV-B stress.
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