An Arabidopsis Mutant Tolerant to Lethal Ultraviolet-B Levels Shows Constitutively Elevated Accumulation of Flavonoids and Other Phenolics

Abstract

The isolation and characterization of mutants hypersensitive to ultraviolet (UV) radiation has been a powerful tool to learn about the mechanisms that protect plants against UV-induced damage. To increase our understanding of the various mechanisms of defense against UVB radiation, we searched for mutations that would increase the level of tolerance of Arabidopsis plants to UV radiation. We describe a single gene dominant mutation (uvt1) that leads to a remarkable tolerance to UVB radiation conditions that would kill wild-type plants. Pigment analyses show a constitutive increase in accumulation of UV-absorbing compounds in uvt1 that increases the capacity of the leaves to block UVB radiation and therefore is likely to be responsible for the elevated resistance of this mutant to UVB radiation. These increases in absorption in the UV region are due, at least in part, to increases in flavonoid and sinapate accumulation. Expression of chalcone synthase (CHS) mRNA was shown to be constitutively elevated in uvt1 plants, suggesting that the increases in absorption may be a consequence of changes in gene expression. Expression of CHS in uvt1 was shown to be still inducible by UV, indicating that the uvt1 lesion may not affect the UV-mediated regulation of CHS gene expression. Our data support an important role for UV screens in the overall protection of plants to UVB radiation. The uvt1 mutant could prove to be an important tool to elucidate further the exact role of UV-absorbing pigments in UV protection as well as the relative contribution of other mechanisms to the overall tolerance of plants to UV radiation.

Retracted: Nitric oxide enhances plant ultraviolet‐B protection up‐regulating gene expression of the phenylpropanoid biosynthetic pathway

“…Flavonoids and anthocyanins were extracted according to Bieza & Lois (2001). One hundred milligrams of leaves were grounded in liquid N2 and flavonoids were extracted for 2 h at 4°C with 400 mL of methanol, centrifuged for 10 min at 10 000 g, and the supernatant was quantified at A330 nm in an Ultrospec 1100 pro spectrophotometer (Amersham Biosciences, Cambridge, UK).…”

Plant L10 Ribosomal Proteins Have Different Roles during Development and Translation under Ultraviolet-B Stress

“…UV-B photons generate photoproducts in DNA and can also directly damage proteins, lipids, and RNA (Britt, 1996;Gerhardt et al, 1999;Casati and Walbot, 2004). Thus, plants have evolved mechanisms of protection (Stapleton and Walbot, 1994), repair (Waterworth et al, 2002;Bergo et al, 2003), and avoidance (Mazza et al, 2000;Bieza and Lois, 2001). Although UV-B photon perception and signal transduction are largely unknown (Brosche and Strid, 2003;Frohnmeyer and Staiger, 2003;Ulm and Nagy, 2005), it was recently shown that the basic domain/Leu zipper transcription factor long hypocotyl 5 (HY5), first identified as a factor for normal growth in visible light, is also an important participant in the long-wavelength (300-315 nm) UV-B light-induced signal transduction cascade in Arabidopsis (Ulm et al, 2004).…”

Plantas medicinais: fatores de influência no conteúdo de metabólitos secundários

“…No caso específico dos flavonóides, estes são acumulados principalmente em tecidos superficiais (tais como epiderme, subepiderme, pêlos, cutícula e material epicuticular) e utilizados pela planta como filtros UV, pois absorvem radiação UV-B sem alterar a radiação fotossinteticamente ativa 101,111,112 . Além disso, também podem atuar como "radical-scavengers" e antioxidantes 108,113 .…”