It is the simplest example of an aryl azo compound
There are also data indicating that epigenetic mechanisms, particularly DNA methylation, are involved in the regulation of stilbene biosynthesis in plants. Treatment of grapevine cell cultures with the DNA demethylation agent 5-azacytosine and the subsequent analysis of STS DNA methylation and transcription levels revealed that the higher level of cytosine DNA methylation within particular STS genes, the lower level of resveratrol was detected in the cell cultures (Kiselev et al. ; Tyunin et al. ). Subsequently, it has been shown that UV-C- and SA-induced accumulation of stilbenes and transcription of STS genes were coupled to a reduction in the cytosine DNA methylation of these STS genes (Kiselev et al. ; Tyunin and Kiselev ). The data suggest that epigenetic mechanisms might directly or indirectly contribute to the stress-induced activation of stilbene biosynthesis.
K. Barry Sharpless -- Publications
Recent studies show that other abiotic stress factors, such as high light and high temperature exposure, could also induce stilbene biosynthesis. Ahn et al. () irradiated grape berries with different light sources (white fluorescent and purple, blue, and red LED lights) and reported that the accumulation of stilbenes and expression of stilbene biosynthesis genes were mainly induced under red and blue LED lightening. Using LC-QTOF-MS-based metabolite profiling, Degu et al. () demonstrated that high light treatment (2500 µmol m−2 s−1) applied to detached Shiraz grape berries led to a transient increase in stilbene levels at pre-veraison (piceid) and veraison (piceid and viniferin) stages, while high temperature (40 °C) specifically induced viniferin content at all sampling times only at the pre-veraison stage. Recent results obtained by Deng et al. () showed that high temperature (40 °C) induced expression of the PAL-, C4H-, 4CL-, and STS-like genes and increased piceatannol levels in the leaves of Gnetum parvifolium, but did not affect resveratrol levels. However, the following analysis revealed that the high temperature conditions inhibited the accumulation of both resveratrol and piceatannol in G. parvifolium stems and roots, while expression of the stilbene biosynthesis genes was increased with some variability (Deng et al. ).
Earlier this year, research at the Kee-Hong Kim lab of Purdue University had preliminary evidence showing that a trans-stilbene compound, Piceatannol, had an ability to inhibit the development of human adipose cells. The mechanism is based around the idea that Piceatannol interacts with a preadipocyte's (immature fat cell) insulin receptors in such a way that surpresses it's growth into a mature adipose cell. Piceatannol is a metabolite of resveratrol, a compoud currently under investigation for possible anti-cancer properites. Piceatannol differs from resveratrol by one hydroxyl group on one of the aromatic rings.
Piceatannol is currently very costly to synthesize. On the advent of such a discovery, we felt that if we were to engineer a pathway to optimize the production of Piceatannol from cheaper substrates through the utilization of our PUF and RNA scaffold projects, we could show the versatility of our PUF toolkit working with an RNA scaffold.
However, before researchers can begin using our PUF toolkit to produce piceatannol in vivo, we took steps to acquire and characterize the necessary genes for our:
Epoxides may be mono- or polyfunctional
Taken together, the data show that the plant phytohormones JA, MeJA, SA, ET, and ABA positively regulate stilbene biosynthesis, while there are no data on the effect of gibberellic acid (GA) and brassinosteroids (BRs), to the best of our knowledge. The precise mechanism of the hormone-mediated regulation of stilbene biosynthesis remains unclear. A study dissecting the transcriptional response to hormone elicitors in V. vinifera cells presented some information on the regulatory cascades activated by MeJA alone or in combination with modified CDs (Almagro et al. ). MeJA up-regulated MYC2, MYC3, and JAZ grapevine transcription factor (TF) genes, which are the main factors regulating the JA responses (Almagro et al. ). In addition, genes encoding other grapevine TFs (WRKY, NAC, ARF2, and MYB), some ethylene signaling proteins, and a putative MAPKKK were markedly up-regulated in the presence of MeJA alone or combined with cyclodextrins (Almagro et al. ). Therefore, the mechanisms transcriptionally activated by MeJA and leading to increased stilbene production could involve these proteins.
They are polymerized by a cationic or an anionic mechanism
In addition to the studies reporting on the positive effect of JA, MeJA, SA, and ET on stilbene production, three recent investigations suggest that abscisic acid (ABA) is involved in the signaling network regulating stilbene biosynthesis in plant cells. First, Nicolas et al. () have shown that overexpression of the gene encoding the abscisic acid response element-binding factor 2 (VvABF2), a grape ABA-responsive basic leucine zipper transcription factor, strongly increased the accumulation of stilbenes (t-resveratrol and t-piceid) in grapevine transgenic cell lines, especially after treatment with ABA. Notably, this study also showed that treatment with ABA itself increased t-resveratrol production in the control (untransformed) grapevine cells (Nicolas et al. ). Then, Kageyama et al. () reported that ABA induced biosynthesis of bisbibenzyls, a group of stilbenoid compounds, in the liverwort Marchantia polymorpha. Recently, Degu et al. () demonstrated that ABA exogenously applied to detached grapevine berries substantially and progressively increased the content of resveratrol, piceid, and viniferin (in berries collected at the pre-veraison but not at veraison stage).