Effects of solar UV-A and UV-B radiation on gene expression and phenolic accumulation in Betula pendula leaves

Abstract

Ultraviolet (UV) radiation is an important environmental factor for plant communities; however, plant responses to solar UV are not fully understood. Here, we report differential effects of solar UV-A and UV-B radiation on the expression of flavonoid pathway genes and phenolic accumulation in leaves of Betula pendula Roth (silver birch) seedlings grown outdoors. Plants were exposed for 30 days to six UV treatments created using three types of plastic film. Epidermal flavonoids measured in vivo decreased when UV-B was excluded. In addition, the concentrations of six flavonoids determined by high-performance liquid chromatography-mass spectrometry declined linearly with UV-B exclusion, and transcripts of PAL and HYH measured by quantitative real-time polymerase chain reaction were expressed at lower levels. UV-A linearly regulated the accumulation of quercetin-3-galactoside and quercetin-3-arabinopyranoside and had a quadratic effect on HYH expression. Furthermore, there were strong positive correlations between PAL expression and accumulation of four flavonols under the UV treatments. Our findings in silver birch contribute to a more detailed understanding of plant responses to solar UV radiation at both molecular and metabolite levels.

An explanation for the natural de-bittering of Hurma olives during ripening on the tree

“…A trend was observed for the rest of the phenolic compounds analyzed in Erkence olives (Table 1), although it was not statistically significant. It must be noted that the synthesis of phenolic compounds is influenced by solar radiation, the longer the hours of exposure to solar radiation of fruit and leaves, the higher the concentration of certain phenolic compounds will be found in these materials (Spayd et al, 2002;Morales et al, 2010).…”

Current Approaches for Enhanced Expression of Secondary Metabolites as Bioactive Compounds in Plants for Agronomic and Human Health Purposes

“…For example, the concentration of phenolic compounds can be increased signifi cantly in blueberries (Vaccinium corymbosum) under UV treatments, also it has been reported that UV radiation induced the fl avonoids biosynthesis that consequently leads to an accumulation of phenolics in the leaves of silver birch (Betula pendula). The elevated ozone environment increased the concentrations of phenolics and antioxidant in red clover (Trifolium pratense) leaves [Morales et al, 2010;Saviranta et al, 2010]. The activity of some pathogens has been limited when phenolic compounds are expressed in some coffee genotypes, showing higher resistance to the leaf miner Leucoptera coffeella, a serious coffee pest [Magalhães et al, 2008].…”

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

“…UV-A and blue light are key factors in the photorepair of DNA damage caused by UV-B. In addition, UV-A and the high irradiance of photosynthetically active radiation (PAR) induce the expression of genes conferring UV protection and the accumulation of phenolics in plants (Ibdah et al, 2002;Götz et al, 2010;Morales et al, 2010).…”

“…In natural environments, plants are usually exposed to high and variable fluxes of PAR and also much higher irradiances of UV-A than of UV-B radiation. Field studies have shown that besides UV-B, solar UV-A regulates gene expression and the accumulation of flavonoids in silver birch (Betula pendula) leaves (Morales et al, 2010). Moreover, it is usually specific compounds rather than the total phenolics that are differentially regulated by different doses of solar UV-A and UV-B radiation (Kotilainen et al, 2009;Morales et al, 2010).…”