Plants utilize a UV-B (280 to 315 nm) photoreceptor UVR8 (UV RESISTANCE LOCUS 8) to sense environmental UV levels and regulate gene expression to avoid harmful UV effects. Uniquely, UVR8 uses intrinsic tryptophan for UV-B perception with a homodimer structure containing 26 structural tryptophan residues. However, besides 8 tryptophans at the dimer interface to form two critical pyramid perception centers, the other 18 tryptophans’ functional role is unknown. Here, using ultrafast fluorescence spectroscopy, computational methods and extensive mutations, we find that all 18 tryptophans form light-harvesting networks and funnel their excitation energy to the pyramid centers to enhance light-perception efficiency. We determine the timescales of all elementary tryptophan-to-tryptophan energy-transfer steps in picoseconds to nanoseconds, in excellent agreement with quantum computational calculations, and finally reveal a significant leap in light-perception quantum efficiency from 35% to 73%. This photoreceptor is the first system discovered so far, to be best of our knowledge, using natural amino-acid tryptophans to form networks for both light harvesting and light perception.
Bibliographical noteFunding Information:
We thank Prof. Yigong Shi (Tsinghua University) for generously providing the UVR8 plasmid, and Prof. Maria-Elisabeth Michel-Beyerle (Nanyang Technological University) for stimulating discussions. This work was supported in part by the National Institute of Health (Grant GM118332 to D.Z. for experiments and GM46736 to J.G. for computation) and the National Natural Science Foundation of China (for support of collaboration effort through a visit of X.L. and a sabbatical stay of D.Z. in Shanghai Jiao Tong University and Grant No. 21533003 to J.G. for support of H.R. to complete computational work).
© 2020, The Author(s).
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't