Abstract
Stilbene compounds belong to a family of secondary metabolites that are derived from the phenylpropanoid pathway. Production of the stilbene phytoalexin, resveratrol, in grape (Vitis spp.) berries is known to be induced by ultraviolet-C radiation (UV-C), which has numerous regulatory effects on plant physiology. While previous studies have described changes in gene expression caused by UV-C light in several plant species, such information has yet to be reported for grapevine. We investigated both the resveratrol content and gene expression responses of berries from V. amurensis cv. Tonghua-3 following UV-C treatment, to accelerate research into resveratrol metabolism. Comparative RNA-Seq profiling of UV-C treated and untreated grape berries resulted in the identification of a large number of differentially expressed genes. Gene ontology (GO) term classification and biochemical pathway analyses suggested that UV-C treatment caused changes in various cellular processes, as well as in both hormone and secondary metabolism. The data further indicate that UV-C induced increases in resveratrol may be related to the transcriptional regulation of genes involved in the production of secondary metabolites and signaling, as well as several transcription factors. We also observed that following UV-C treatment, 22 stilbene synthase (STS) genes exhibited increases in their expression levels and a VaSTS promoter drove the expression of the GUS reporter gene when expressed in tobacco. We therefore propose that UV-C induction of VaSTS expression is an important factor in promoting resveratrol accumulation. This transcriptome data set provides new insight into the response of grape berries to UV-C treatment, and suggests candidate genes, or promoter activity of related genes, that could be used in future functional and molecular biological studies of resveratrol metabolism.
Highlights
Stilbenes, which are a small family of secondary metabolites derived from the phenylpropanoid pathway, are produced in a taxonomically broad range of plant species and have been associated with both enhancing plant disease resistance and having a positive effect on human health as a dietary component (Chong et al, 2009)
The highest levels of resveratrol were found in V. amurensis Tonghua3 (2.19 μg/g FW at maturity); this genotype was chosen for further study
While numerous studies to date have investigated the effect of UV radiation on diverse plant species, most have focused on the biosynthesis and accumulation of various metabolites in response to UV-B radiation
Summary
Stilbenes, which are a small family of secondary metabolites derived from the phenylpropanoid pathway, are produced in a taxonomically broad range of plant species and have been associated with both enhancing plant disease resistance and having a positive effect on human health as a dietary component (Chong et al, 2009). Resveratrol has been suggested to have health benefits associated with a moderate consumption of red wine (Siemann and Creasy, 1992), and many studies have reported that it can prevent, or slow, the progression of a wide variety of illnesses, including cancer and cardiovascular disease, and that it may even extend the lifespan of various organisms (Baur and Sinclair, 2006). As such, it is one of the most extensively studied natural products. As a result of the potentially damaging effects of UV radiation, plants have evolved a number of sophisticated mitigation mechanisms, such as the accumulation of UV-absorbing phenolic and flavonoid molecules in epidermal cells to reduce light penetration, and the activation of antioxidant defenses to limit photo-oxidative damage (Hollósy, 2002; Kasim et al, 2008)
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