Ultraviolet-B acclimation is supported by functionally heterogeneous phenolic peroxidases

• Published in: Scientific reports Vol. 10; no. 1; p. 16303
• Main Authors: Rácz, Arnold, Czégény, Gyula, Csepregi, Kristóf, Hideg, Éva
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.10.2020; Nature Publishing Group
• Subjects: 631/449/2661; 631/449/2667; 631/449/2686; Acclimation; Acclimatization; Antioxidants; Antioxidants - metabolism; Chlorogenic acid; Heterogeneity; Humanities and Social Sciences; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Isoforms; Leaves; multidisciplinary; Nicotiana - enzymology; Nicotiana - radiation effects; Peroxidase; Peroxidases - metabolism; Peroxidases - physiology; Phenolic compounds; Phenols; Phenols - metabolism; Photosynthesis; Plant Proteins - metabolism; Plant Proteins - physiology; Quercetin; Science; Science (multidisciplinary); Tobacco; Ultraviolet radiation; Ultraviolet Rays
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-73548-5

Tobacco plants were grown in plant chambers for four weeks, then exposed to one of the following treatments for 4 days: (1) daily supplementary UV-B radiation corresponding to 6.9 kJ m −2 d −1 biologically effective dose (UV-B), (2) daily irrigation with 0.1 mM hydrogen peroxide, or (3) a parallel application of the two treatments (UV-B + H 2 O 2 ). Neither the H 2 O 2 nor the UV-B treatments were found to be damaging to leaf photosynthesis. Both single factor treatments increased leaf H 2 O 2 contents but had distinct effects on various H 2 O 2 neutralising mechanisms. Non-enzymatic H 2 O 2 antioxidant capacities were increased by direct H 2 O 2 treatment only, but not by UV-B. In contrast, enzymatic H 2 O 2 neutralisation was mostly increased by UV-B, the responses showing an interesting diversity. When class-III peroxidase (POD) activity was assayed using an artificial substrate (ABTS, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)), both treatments appeared to have a positive effect. However, only UV-B-treated leaves showed higher POD activities when phenolic compounds naturally occurring in tobacco leaves (chlorogenic acid or quercetin) were used as substrates. These results demonstrate a substrate-dependent, functional heterogeneity in POD and further suggest that the selective activation of specific isoforms in UV-B acclimated leaves is not triggered by excess H 2 O 2 in these leaves.