Fig. 7: Proposed mechanism for stabilization of monomeric UVR8 by naringenin chalcone (NGC) derivatives and its effects on UVR8-mediated gene regulation.
From: Flavonoid pathway intermediates implicate UVR8 in functions beyond canonical UV-B signaling
a Under growth chamber light conditions, UVR8 predominantly exists in the cytosol as an inactive homodimer. A minor fraction of UVR8 is present in the nucleus in its monomeric form, where it interacts with COP1 (E3 ubiquitin ligase) to inhibit COP1-mediated degradation of HY5. Defense-related genes I are activated by endogenous SA. b Under natural sunlight conditions, accumulated NGC derivatives elevate SA levels and directly bind to UVR8 monomers. This SA accumulation leads to the activation of defense-related genes II. The formation of monomeric UVR8-NGC derivative complex promotes the activation of a subset of UVR8-regulated genes that don’t require UV-B signaling. COP1, CONSTITUTIVELY PHOTOMORPHOGENIC1; HY5, ELONGATED HYPOCOTYL5; NGC, naringenin chalcone; SA, salicylic acid; UVR8, UV RESISTANCE LOCUS8.
