Multiple Roles for UV RESISTANCE LOCUS8 in Regulating Gene Expression and Metabolite Accumulation in Arabidopsis under Solar Ultraviolet Radiation    

Abstract

Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280-315 nm) are mediated by the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8). Beyond our understanding of the molecular mechanisms of UV-B perception by UVR8, there is still limited information on how the UVR8 pathway functions under natural sunlight. Here, wildtype Arabidopsis (Arabidopsis thaliana) and the uvr8-2 mutant were used in an experiment outdoors where UV-A (315-400 nm) and UV-B irradiances were attenuated using plastic films. Gene expression, PYRIDOXINE BIOSYNTHESIS1 (PDX1) accumulation, and leaf metabolite signatures were analyzed. The results show that UVR8 is required for transcript accumulation of genes involved in UV protection, oxidative stress, hormone signal transduction, and defense against herbivores under solar UV. Under natural UV-A irradiance, UVR8 is likely to interact with UV-A/blue light signaling pathways to moderate UV-B-driven transcript and PDX1 accumulation. UVR8 both positively and negatively affects UV-Aregulated gene expression and metabolite accumulation but is required for the UV-B induction of phenolics. Moreover, UVR8-dependent UV-B acclimation during the early stages of plant development may enhance normal growth under long-term exposure to solar UV.

The UVR8 UV-B Photoreceptor: Perception, Signaling and Response

“…Moreover, the effect of UV-B on pathogen resistance was found to be mediated by UVR8 (Demkura and Ballare 2012). A role for UVR8 remains to be established in a number of other UV-B responses in Arabidopsis, including stomata regulation (Eisinger et al 2003), phototropism (Eisinger et al 2003, Shinkle et al 2004, dynamics of phytohormones under UV-B (Savenstrand et al 2004, Hectors et al 2012, vitamin B6 biosynthesis (Brosche et al 2002, Ristilä et al 2011, Morales et al 2013) and alterations in secondary metabolism (Jansen et al 2008, Kusano et al 2011. A number of further UVR8-mediated responses can be deduced from UV-B-induced and UVR8-dependent gene expression changes (Brosche et al 2002, Ulm et al 2004, Brown et al 2005, Oravecz et al 2006, Hectors et al 2007, Zhou et al 2007, Favory et al 2009, Morales et al 2013) but these remain to be validated.…”

“…flavonol glycosides) (Kliebenstein et al 2002, Favory et al 2009, Morales et al 2013 (Figure 7). Such responses are brought about by UV-B-induced expression of a range of genes (Kliebenstein et al 2002, Ulm et al 2004, Brown et al 2005, Favory et al 2009).…”

Singlet oxygen scavenging by leaf flavonoids contributes to sunlight acclimation in Tilia platyphyllos

“…During photoinhibition by excess PAR singlet oxygen ( 1 O 2 ) is photoproduced by the reaction mutant Arabidopsis leaves suggested an interaction of UVR8 with other photoreceptors to 1 modulate UV-A responses in the presence of UV-B (Morales et al 2013). …”

Stress Responses of Peanut (<i>Arachis hypogaea</i> L.) Genotypes as Measured by Trigonelline Content after Exposure to UV-B Radiation

“…Plant growth stages may play an important role in stress response as individuals at R7 had trigonelline concentrations 47.3% to 52.4% higher than individuals at R1. Plant age may be a more important variable than genotypic variability for the development of UV-B tolerant peanut crops [41]. Comparative transcriptomic study of UV-B responsive genes across multiple plant growth stages could clarify the differential expression in secondary metabolite biosynthesis due to plant age and could provide a stronger basis for the development of UV-B resistant crops.…”