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. 2019 Dec 7;20(24):6185. doi: 10.3390/ijms20246185

Figure 6.

Figure 6

Proposed model of the molecular mechanism leading to the high accumulation of resveratrol after treatment with UV-C in Polygonum cuspidatum leaf. Deamination of phenylalanine ammonia by phenylalanine ammonia-lyase (PAL) is the first step in the resveratrol biosynthesis pathway. Then, the conversions of cinnamic acid into p-coumaric acid and subsequently into 4-coumarate-CoA are catalyzed by cinnamic acid 4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL), respectively. The last step in the pathway consists of the conversion of one 4-coumarate-CoA and three malonyl-CoA units into resveratrol or naringenin chalcone by stilbene synthase (STS) or chalcone synthase (CHS), respectively. Later, resveratrol is converted into pterostilbene by resveratrol O-methyltransferase (ROMT). PAL, C4H, 4CL and STS were found strongly up-regulated in PC6H and PC12H as compared to PC, while CHS displayed the opposite trend. STS and CHS share the same substrate. P. cuspidatum tends to prioritize resveratrol accumulation by diverting the substrate “one 4-coumarate-CoA and three malonyl-CoA units” to the resveratrol synthesis pathway over the naringenin chalcone synthesis pathway through up-regulation of STS genes and down-regulation of CHS genes in response to UV-C exposure. High induction of ROMT also suggests that pterostilbenes may also be accumulated. PC, PC6H and PC12H represent samples collected before, 6 h and 12 h after UV-C treatment, respectively.