Insights into hydrogen sulfide defense against black rot of cabbage at morphological, cellular and transcriptional metabolic levels

Black rot caused by Xanthomonas campestris pv. campestris (Xcc) has resulted in severe damage to cabbage yields worldwide. Hydrogen sulfide (H₂S), an important gaseous signaling molecule, is involved in mediating plant defense responses to various adversity stresses. However, few studies have investigated how H₂S enhances resistance mechanisms in plants under biotic stress. Therefore, in this experiment, we investigated the effects of exogenous H₂S on the extent of plant-pathogen interactions, antioxidant mechanisms, plant pathogenesis, cellular integrity and accumulation of secondary metabolite under Xcc infested cabbage. Our study showed that Xcc inhibited the antioxidant properties and secondary metabolites synthesis of cabbage, led to significant disruption of cell wall and cell membrane integrity, which triggered severe plant diseases. The use of H₂S effectively mitigated this inhibitory effect and the extent of damage, up-regulated the expression levels of genes involved in plant-pathogen interactions, stabilized the osmoregulatory system, improved the antioxidant capacity, promoted the GSH-ASA cycle, protected cellular integrity, mitigated the extent of morbidity and enhanced the rate of substance synthesis. Thus, H₂S could improve the disease resistance of cabbage seedlings and relieved the negative effects of Xcc.