Fig. 4: Decreased proline levels contribute to decreased T3SS- and growth-inducing activity of apoplastic wash fluid from flg22-treated Arabidopsis leaves.

a Absolute quantification of proline levels in apoplastic wash fluid (AWF) from mock-and flg22-treated leaves. Graphed are means ± SE of proline abundance, n = 8. Data were pooled from eight independent experiments. b, c P. syringae DC3000 hrpL_promoter:gfp were cultured in (b) minimal medium containing 10 mM fructose and supplemented with or without 100 µM proline, or (c) in mock- and flg22-AWF supplemented with or without 100 µM proline. Graphed are means ± SE of normalized GFP fluorescence, n = 3. d Growth of P. syringae DC3000 hrpL_promoter:gfp in mock- and flg22-AWF isolated from Col-0 leaves and supplemented with or without 100 µM proline. Graphed are means of culture optical density at λ = 600 nm ± SE, n = 3. Data in b–d are representative of three independent experiments. Asterisks in panels a and b denote significance based on two-sided t-test, ***p < 0.001. Lower case letters in c and d denote significance groupings based on ANOVA with Tukey’s HSD, p < 0.05.