A role for β,β-xanthophylls in Arabidopsis UV-B photoprotection

• Published in: Journal of experimental botany Vol. 69; no. 20; pp. 4921 - 4933
• Main Authors: Emiliani, Julia, D'Andrea, Lucio, Lorena Falcone Ferreyra, María, Maulión, Evangelina, Rodriguez, Eduardo, Rodriguez-Concepción, Manuel, Casati, Paula
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 14-09-2018
• Subjects: MEP pathway; violaxanthin; xanthophylls; Isoprenoids; UV-B damage; zeaxanthin
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/ery242

Carotenoids have a role in UV-B photoprotection in Arabidopsis thaliana and this requires β,β-xanthophylls, but not other plastidial isoprenoids.
Abstract
Plastidial isoprenoids, such as carotenoids and tocopherols, are important anti-oxidant metabolites synthesized in plastids from precursors generated by the methylerythritol 4-phosphate (MEP) pathway. In this study, we found that irradiation of Arabidopsis thaliana plants with UV-B caused a strong increase in the accumulation of the photoprotective xanthophyll zeaxanthin but also resulted in slightly higher levels of γ-tocopherol. Plants deficient in the MEP enzymes 1-deoxy-D-xylulose 5-phosphate synthase and 1-hydroxy-2-methyl-2-butenyl 4-diphosphate synthase showed a general reduction in both carotenoids and tocopherols and this was associated with increased DNA damage and decreased photosynthesis after exposure to UV-B. Genetic blockage of tocopherol biosynthesis did not affect DNA damage accumulation. In contrast, lut2 mutants that accumulate β,β-xanthophylls showed decreased DNA damage when irradiated with UV-B. Analysis of aba2 mutants showed that UV-B protection was not mediated by ABA (a hormone derived from β,β-xanthophylls). Plants accumulating β,β-xanthophylls also showed decreased oxidative damage and increased expression of DNA-repair enzymes, suggesting that this may be a mechanism for these plants to decrease DNA damage. In addition, in vitro experiments also provided evidence that β,β-xanthophylls can directly protect against DNA damage by absorbing radiation. Together, our results suggest that xanthophyll-cycle carotenoids that protect against excess illumination may also contribute to protection against UV-B.