UVR8 Mediates UV-B-Induced Arabidopsis Defense Responses against Botrytis cinerea by Controlling Sinapate Accumulation

Abstract

Light is emerging as a central regulator of plant immune responses against herbivores and pathogens. Solar UV-B radiation plays an important role as a positive modulator of plant defense. However, since UV-B photons can interact with a wide spectrum of molecular targets in plant tissues, the mechanisms that mediate their effects on plant defense have remained elusive. Here, we show that ecologically meaningful doses of UV-B radiation increase Arabidopsis resistance to the necrotrophic fungus Botrytis cinerea and that this effect is mediated by the photoreceptor UVR8. The UV-B effect on plant resistance was conserved in mutants impaired in jasmonate (JA) signaling (jar1-1 and P35S:JAZ10.4) or metabolism of tryptophan-derived defense compounds (pen2-1, pad3-1, pen2 pad3), suggesting that neither regulation of the JA pathway nor changes in levels of indolic glucosinolates (iGS) or camalexin are involved in this response. UV-B radiation, acting through UVR8, increased the levels of flavonoids and sinapates in leaf tissue. The UV-B effect on pathogen resistance was still detectable in tt4-1, a mutant deficient in chalcone synthase and therefore impaired in the synthesis of flavonoids, but was absent in fah1-7, a mutant deficient in ferulic acid 5-hydroxylase, which is essential for sinapate biosynthesis. Collectively, these results indicate that UVR8 plays an important role in mediating the effects of UV-B radiation on pathogen resistance by controlling the expression of the sinapate biosynthetic pathway.

Canopy Light and Plant Health

“…1). UV-B radiation has also been reported to increase plant resistance to microbial pathogens (Gunasekera et al, 1997;Wargent et al, 2006;Gunasekera and Paul, 2007;Kunz et al, 2008;Demkura and Ballaré, 2012) and can interact with the plant to modify the composition of microbial communities in the phyllosphere (Kadivar and Stapleton, 2003;Balint-Kurti et al, 2010). Treatment with unnaturally high doses of UV-B radiation, or with UV wavelengths not present in the daylight spectrum (UV-C, l , 280 nm), has also been reported to activate defense-related pathways in several species (Bridge and Klarman, 1973;Brederode et al, 1991;Conconi et al, 1996;Mert-Turk et al, 2003;Glawischnig, 2007); however, the ecological significance of these responses is not clear.…”

“…(Stratmann et al, 2000;Izaguirre et al, 2003;Demkura et al, 2010). However, synergistic effects of UV-B and JA elicitation have not been observed for several classic markers of the JA response in Arabidopsis (Arabidopsis thaliana; Demkura and Ballaré, 2012). Similarly, mixed results have been obtained regarding the effects of UV-B radiation on JA accumulation (A-H- Mackerness et al, 1999;Demkura et al, 2010).…”

Reversion of the Arabidopsis UV-B photoreceptor UVR8 to the homodimeric ground state

“…Specific UV-B perception is facilitated by the photoreceptor UV RESISTANCE LOCUS 8 (UVR8) identified only recently in Arabidopsis (7). In agreement with its photoreceptor function, uvr8 null mutants show a strongly reduced response to UV-B (8)(9)(10)(11), which even is absent under conditions specifically activating UV-B photoreceptor responses (4). In contrast, UV-B stress responses are not affected per se in uvr8 mutants (12).…”

Cloning and Construction of Overexpression Vector for FaUVR8 Gene Transformation with Strawberry

“…Studies have shown that UVR8 can stimulate the biosynthesis of acid salt enhanced plant resistance to Botrytis cinerea [8], Botrytis cinerea [9] is an important disease of strawberry harm of protected cultivation, the control methods mainly rely on chemical agents, long-term use of this kind of medicament not only makes strawberry resistance to Botrytis cinerea, and serious pollution the environment is not conducive to agricultural products, production and sales. If the overexpression of strawberry FaUVR8 can be confirmed, the plant resistance to Botrytis cinerea can be significantly improved, which will be of great significance in the production practice.…”