Flavonols protect Arabidopsis plants against UV-B deleterious effects

Abstract

Flavonols are synthesized by flavonol synthase (FLS) enzymes (Martens et al., 2010). These compounds absorb UV-B light in the 280?320 nm region, and their concentration increases in plants exposed to environmental abiotic and biotic stresses, including UV-B; consequently, flavonols are thought to act as UV-B filters (Agati et al., 2011). It has been also suggested that these metabolites function as reactive oxygen species (ROS) scavengers, as they contain an OH- group in the 3-position of the flavonoid skeleton, which allows them to chelate metals, inhibiting the formation of free radicals and ROS accumulation, once formed (Agati et al., 2009). For these reasons, it has been suggested that flavonols play uncharacterized roles in UV responses (Verdan et al., 2011). Nevertheless, despite the fact that the role of flavonols in UV-B protection has been inferred; the protection conferred by flavonols on the target sites of UV-B-damage has not been directly proven in planta. Recently, we demonstrated that maize FLS1 (ZmFLS1) complements the flavonol deficiency of the Arabidopsis fls1 mutant and decreases its high level of anthocyanins, characteristic of this mutant plant (Falcone Ferreyra et al., 2010). In order to demonstrate that flavonols protect plants against UV-B damage, we generated Arabidopsis transgenic plants overexpressing the maize FLS1 cDNA (35S:ZmFLS1), and evaluated different responses of these transgenic plants against UV-B damage.