Oxidised glutathione-regulated plant cell death of Chinese cabbage leaves against adapted and non-adapted Xanthomonas species

Reduced and oxidised glutathione (GSH and GSSG) and buthionine sulfoximine (BSO) were applied to Xanthomonas campestris pv. campestris (Xcc) and X. vesicatoria (Xv) during liquid cultures, and to Chinese cabbage seedlings to decipher the roles of glutathione in the plant immunity against an adapted Xcc and a non-adapted Xv. In vitro antibacterial activities of GSH, GSSG and BSO were evaluated in Xcc and Xv cultures after 24 h and 48 h, respectively. GSH and GSSG exhibited in vitro antibacterial activities against Xcc and Xv, but BSO did not. In planta, GSH did not change the Xcc-caused tissue damage, but GSSG reduced leaf damage caused by Xcc infection at 2 and 3 d. BSO accelerated the damage. Neither GSH, GSSG, nor BSO altered gradually increasing Xcc bacterial growth in the mock-treated leaves. GSSG decreased Xv-triggered electrolyte leakage at 24 h and reduced Xv bacterial growth in the leaves at 7 d. In conclusion, exogenous GSH, GSSG and BSO treatments altered reactive oxygen species (ROS) and nitric oxide (NO) levels in the leaves before bacterial inoculation, and these changes led to differences in tissue damage in inoculated leaves.