March 2022 ESRFnews16

STRUCTURAL BIOLOGY

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F C A N D É / E

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At the ESRF s ID23-2 beamline, Zubieta and her colleagues have discovered how the evening complex protein affects the response of plants to warmer temperatures early in the year.

Zubieta became interested in the evening complex at a conference back in 2014 when she met Philip Wigge, a biologist studying it at the University of Cambridge in the UK (he is now at the University of Potsdam and the Leibniz Institute for Vegetable and Ornamental Crops in Grossbeeren, Germany), whom she later came to work with. At the time, she knew the evening complex was tricky territory for a structural biologist. One of its pro- teins, EARLY FLOWERING 3 (ELF3), is largely disor- dered a challenge for protein crystallography and the basic mantra that structure determines function. Zubieta was hopeful that the complex s ordered parts would be sufficient to betray that function. In fact, the evening complex has three components: the

scaffold protein ELF3, as well as the small peptide ELF4 and a DNA-binding protein, LUX. In 2020, Zubieta and her team came to the ESRF s ID23-2 and ID29 beamlines to solve the structure of the domain of LUX that binds to DNA. Together with work performed by the researchers

collaborators in Germany, the Spanish National Research Council and the National Institute of Science Education and Research in Bhubaneshwar, India, the results showed that LUX recruits ELF3 and ELF4 in a specific manner, with ELF3 decreasing LUX s binding ability and ELF4 restoring it. Meanwhile, in vitro studies performed by Stephanie Hutin in Zubieta s team revealed that the evening complex binds more weakly to DNA as the temperature increases. The message: it is the binding of the complex to DNA that restrains flowering. At higher temperatures, ELF3 stops that binding making it important for the elongation growth and flowering of plants earlier in the year when the temperature is warm (PNAS 117 6901). If we can make the evening complex bind to DNA bet-

ter, it may slow down growth and entry into reproduction, explains Zubieta. At this time, when climate change is a reality, the evening complex could be very useful as a way to tune growth under warmer conditions. Zubieta s team is currently investigating ways to stabilise the binding of the evening complex even under higher temperatures to slow down growth and early flowering. Follow-up experiments using an ELF3 mutant expressed

in A. thaliana demonstrated the same resilience to early flowering. But this did not explain how the original ELF3 responds the way it does. Zubieta and colleagues found a clue in the disordered region of ELF3 that is enriched in polar amino-acid residues and depleted of charged

With climate change a reality, the evening complex could be very useful as a way to tune growth under warmer conditions