a, View of P1.1. b, Orthogonal view. c, View of P1.2 element of Lettuce. d, Orthogonal view of c. e, Fluorescence of site-directed mutants of P1.1 and P1.2 in the presence of DFHBI-1T, normalized to wild-type (mean ± s.d., n ≥ 3). Striped bar, A14T•T29, T15G•T28C mutant. f, Fluorescence of Lettuce constructs with shortened P1 in the presence of DFHBI-1T, normalized to wild-type (mean ± s.d., n ≥ 3). g, Schematic of circular permutation. h, Fluorescence of Lettuce constructs with permuted P1 (P1cp) in the presence of DFHBI-1T, normalized to wild-type (mean ± s.d., n ≥ 3). i, Fluorescence of Lettuce mutant A14T•T29, T15G•T28C and shortened P1cp in the presence of DFHBI-1T, normalized to wild-type (mean ± s.d., n ≥ 3).