A. Representative photo of transgenic bioluminescent Nicotiana benthamiana leaves injected with solution of individual hispidin precursors. The images are representative of four experiments repeated independently with similar results B, C. Injections of hispidin and luciferin in leaves of bioluminescent and wild-type N. benthamiana plants. The experiment was repeated twice independently with similar results. D. Box plots showing luminescence response at sites of injections of mixtures of hispidin precursors of various compositions. Data points are shown, Luminescence change is absolute change of signal (ΔL = luminescence after injection – initial luminescence). Strikethrough text highlights the absence of a compound in the mixture. Notably, only mixtures containing caffeic acid induced the increase of luminescence. The box extends from the lower to upper quartile values of the data, orange line represents the median. Whiskers represent a full data range. Groups containing multiple reagens (Kruskal-Wallis H Test, H-statistic=48.59, p=7.11e-10) and single potential reagents (Kruskal-Wallis H Test, H-statistic: 68.65, p=8.3e-15) were analyzed separately. P-values of post-hoc pairwise Mann-Whitney U-tests highlighting the effect of caffeic acid on the luminescence response are indicated below the brackets between the box plots E. Effect of injections of three successive luciferin precursors on the intensity of luminescence of N. benthamiana leaves.