Fig. 1

Non-destructive visualisation and quantification of leaf colonisation by bioluminscent P. syringae pv. tomato D3000 expressing the luxCDABE operon from Photorhabdus luminescens (Pst::LUX). A Representative example of the spatial–temporal pattern Pst::LUX colonisation in a hyper-susceptible NahG plant of Arabidopsis. Top panels show black and white images of the plant taken under bright field illumination. Bottom panels show bacterial bioluminescence acquired from the same plant by a quantum efficiency CCD camera in complete darkness. Red outlines indicate the plant surface area obtained from the bright field images. B Quantification of Pst::LUX colonisation of Arabidopsis plants that vary in salicylic acid (SA)-dependent resistance. Bacterial bioluminescence was measured in hyper-susceptible NahG, wild-type Col-0 and Col-0 pretreated with 250 μM of the resistance-inducing SA analogue BTH. Data represent relative bioluminscence values normalised by leaf surface area per plant. Statistically significant differences between genotypes/treatments at each time-point (letters) were assesed by one-way ANOVA, followed by Tukey’s post-hoc for multiple comparisons (p < 0.05). Error bars represent standard errors of the mean (n = 24). C Quantification of Pst::LUX colonisation of tomato plants (cv. MoneyMaker) that vary in SA-dependent resistance. Bioluminescence was measured in plants pre-treated with water (mock; susceptible) or 2.5 mM SA (resistant). Data represent relative bioluminscence values normalised by leaf surface area per plant. Statistically significant differences between treatments at each time-point were assesed by a Student’s t-test (*p < 0.05; ***p < 0.001). Error bars represent standard error of the mean (n = 15). dpi: days post inoculation