# Impact of Environmental Factors on Stilbene Biosynthesis
## 3 Impact of Environmental Factors on the Biosynthesis of Stilbenes
### Temperature  
Temperature is an environmental factor of primary importance for plants. It is among the most crucial climatic drivers of biodiversity [274; 275] and significantly affects gene expression, protein synthesis, enzymatic activity, and overall primary and secondary metabolism [276; 277; 278]. Numerous studies have investigated the influence of temperature on the biosynthetic pathway of polyphenols, but only a small fraction of these have focused on stilbenes [204; 205; 206; 207] (Table 1). A recent study on _Gnetum parifolium_ revealed that exposure to high temperature (40 \({}^{\circ}\)C) enhances resveratrol and piceatannol biosynthesis in leaves of young seedlings, as well as increasing the expression of five _STS_-like genes in leaves of mature trees, fruit flesh, and seeds [204]. Subsequently, the same authors confirmed the increased expression of _STS_-like genes under high temperature; however, they did not find a significant increase in the accumulation of total stilbenes in stems and roots of one-year-old plants, suggesting an influence from post-transcriptional regulation on stilbene biosynthesis [205]. The impact of temperature on stilbene biosynthesis was also investigated in grapevines on whole plants, post-harvested fruits, and cultured cells. In 2017, [PERSON] and co-workers [206] analyzed the entire transcriptome of the berry skin in _V. vinifera_ cv. San-giovese during ripening under high temperature or low temperature regimes characterized respectively by 26 and 21 \({}^{\circ}\)C as average and 42 and 35 \({}^{\circ}\)C as maximum daily air temperature. They observed an inhibitory effect of high temperatures on stilbene biosynthesis, in contrast to low temperatures that induced the expression of several members of _STS_ and _PAL_ multigene families, indicating the activation of stilbene biosynthesis. A coordinated expression of _STS_ and _PAL_ has been often observed in grape berries, suggesting that several enzymatic steps in the stilbene biosynthetic pathway are co-regulated [279]. An inhibitory effect of high temperature on the stilbene biosynthetic pathway in grapevine was also reported by [PERSON] et al. [280] and [PERSON] et al. [207]. Several studies investigated the impact of post-harvest temperature treatment on stilbene biosynthesis. Grapes stored at 0 \({}^{\circ}\)C showed a cultivar-dependent modulation in the expression of _STS_ genes, as well as in the accumulation of resveratrol, resveratrol-glucoside, _trans_-piceatannol, z-miyabenol, and pallidol, especially in the Red Globe cultivar [208; 209]. Grape berries cv. Shiraz exposed to high temperature (40 \({}^{\circ}\)C) showed an increase in viniferin content, which was accompanied by a decrease in the resveratrol and picedi content [210]. It was also reported that cold storage in combination with UV-C enhanced _cis_- and _trans_piceid content in cv. Red Globe berries stored at 4 \({}^{\circ}\)C, while no increase of picoids was obtained by UV-C postharvest treatment alone [196]. Different wilting conditions during winemaking were also investigated by [PERSON] and co-workers [185], revealing an increase of resveratrol and _STS_ mRNA under traditional (ambient temperature for 100 days), low temperature (28 \({}^{\circ}\)C for 15 days), and mixed temperature (45 \({}^{\circ}\)C for 36 h, ambient temperature for 94 d) wilting, especially with the latter method. No increase in resveratrol was reported with high temperature (45 \({}^{\circ}\)C for 110 h) wilting. Temperature-dependent resveratrol accumulation was observed by [PERSON] and colleagues [217], who reported an optimal range for _trans_-resveratrol biosynthesis at 15-20 \({}^{\circ}\)C, a delayed accumulation of this stilbene at 5 \({}^{\circ}\)C, and inhibition at -20 \({}^{\circ}\)C and under heat shock (65 \({}^{\circ}\)C for 2 h immediately after cane harvest, followed by storage at 20 \({}^{\circ}\)C).