The strigolactone hormones govern plant growth and development. A nasty parasitic weed, Striga, senses traces of these hormones to identify its targets. After functionally characterizing several strigolactone receptors from Striga, Toh et al. solved the crystal structure of one that is especially sensitive. The structure shows an unexpectedly large ligand-binding pocket, which may explain how Striga manages to sense picomolar concentrations of the range of strigolactones.
S. Toh, D. Holbrook-Smith, P. J. Stogios, O. Onopriyenko, S. Lumba, Y. Tsuchiya, A. Savchenko, P. McCourt, Structure-function analysis identifies highly sensitive strigolactone receptors in Striga. Science 350, 203–207 (2015). [Abstract] [Full Text]