Physiological and molecular mechanisms of melatonin to alleviate benzoic acid-induced autotoxicity stress in Prunus persica

Autotoxicity stress is well known as a critical factor in the replant problem that hinders the sustainable development of agriculture. Benzoic acid (BA) is identified as a major autotoxin in peach replant problem, and causes serious growth inhibition of peach plants. Melatonin is a multi-functional molecule that plays a key role in alleviating stress-induced damage in plants. However, the functions and the inherent molecular mechanisms of melatonin under autotoxicity stress remains largely elusive. Here, we found that application of melatonin significantly enhanced BA tolerance in peach seedlings. Exogenous melatonin mitigated the negative impact of BA stress on peach root growth. Melatonin pretreatment boosted flavonoid biosynthesis and increased soluble sugar content of peach plants under BA stress. In addition, melatonin also promoted the reactive oxygen species scavenging by enhancing the antioxidant capacity. Consistent with these alterations, transcriptome analysis demonstrated that up-regulations of flavonoid biosynthesis, starch and sucrose metabolism, and antioxidant-related genes were observed when melatonin applied under BA stress. Furthermore, we also observed that an induction in genes involved in xenobiotic transmembrane transport, cell wall organization or biogenesis, and α-linolenic acid metabolism, which might contribute to the melatonin-mediated BA tolerance. Collectively, our findings reveal that melatonin confers BA tolerance of peach seedlings, primarily attributed to increased flavonoid and soluble sugar levels, enhanced antioxidant capacities, and extensive transcriptome reprograming. This opens new avenues for utilizing melatonin to alleviate peach replant problem. •Melatonin significantly enhanced benzoic acid tolerance in peach seedlings.•Melatonin pretreatment boosted flavonoid biosynthesis under benzoic acid stress.•Melatonin improved soluble sugar contents and antioxidant capacities.•Extensive transcriptome reprogram contributed to the melatonin-mediated benzoic acid tolerance.