UV-B shock induces photoprotective flavonoids but not antioxidant activity in Antarctic Colobanthus quitensis (Kunth) Bartl

Abstract

Colobanthus quitensis, the only dicot that inhabits Antarctica, is subjected to different abiotic factors such as high UV-B levels in spring-summer. Several authors described the flavonoid biosynthesis as crucial to tolerating UV-B enriched environments. The goal of this work is the study of the relationship between biosynthesis of flavonoids, resistance to high UV-B levels and the maintenance of redox homeostasis. With this objective, C. quitensis plantlets were subjected to low, medium and high levels of UV-B radiation, in the presence and absence of aminooxiacetic acid (AOA), a phenylalanine ammonia-lyase (PAL) inhibitor with the aim to determine the role of flavonoids in the capacity of C. quitensis to survive to UV-B. The results showed that plants subjected to increasing levels of UV-B, in the absence of the inhibitor, did not present oxidative damage; on the other hand, plants that were treated by the inhibitor showed oxidative stress symptoms and photosynthetical damage. Oxidative damage was correlated with flavonoids content; at the molecular level, these results showed an increase in transcript levels related to the phenylpropanoid pathway enzymes and their activity, as well as the expression of the UVR8−COP1-HY5 transduction system. Moreover, in AOA treated plants, the results show significant damage and plant death. Our results suggest that the survival mechanism showed by C. quitensis to UV-B radiation is mediated by biosynthesis of flavonoids.