Black rot, caused by Xanthomonas campestris pv. campestris ( Xcc ), is a devastating disease in cabbage. As a gaseous signaling molecule, hydrogen sulfide (H 2 S) is widely involved in plant disease resistance. However, the mechanism by which H 2 S enhances resistance to Xcc remains unclear. In our study, we demonstrate that exogenous H 2 S significantly enhances cabbage resistance to black rot by enhancing the phenylpropanoid pathway and antioxidant system. Physiological and biochemical analyses revealed that H 2 S pretreatment boosted endogenous H 2 S and nitric oxide (NO) levels by over 18.8% and 107.7%, respectively, and increased the contents of lignin and tannin by more than 16%. Concurrently, H 2 S reduced hydrogen peroxide (H 2 O 2 ) accumulation by 10.9% and the superoxide anion (O 2 − ) production rate by 42.2%, while enhancing the scavenging rates of superoxide and hydroxyl radicals. Physiological and biochemical results indicated that H 2 S application markedly promoted the accumulation of key phenolic acids, including protocatechuic acid (108.2%), chlorogenic acid (40.8%), and ferulic acid (68.9%), by upregulating the activities and related gene ( PAL , C4H , COMT ) expression level of pivotal enzymes. Integrated transcriptomic and metabolomic analyses further confirmed that H 2 S activated the phenylpropanoid biosynthesis pathway. Our findings providing new insights into the molecular mechanism of H 2 S-mediated disease resistance and a potential strategy for controlling black rot.
Liu et al. (Fri,) studied this question.