Lasiodiplodia theobromae-induced alteration in ROS metabolism and its relation to gummosis development in Prunus persica

Peach gummosis caused by Lasiodiplodia theobromae is one of the most detrimental diseases to peaches in southern China. Reactive oxygen species (ROS) play major roles in plant-pathogen interactions, however, their roles in the pathogenesis of peach gummosis, especially shoot disease in perennials, are largely unknown. In this study, the effects of L. theobromae on ROS production-scavenging systems and on signalling transduction during L. theobromae-induced gummosis in current-year peach shoots were investigated. The infection by L. theobromae led to a ROS burst and activated the plant antioxidant enzyme-dependent scavenging system. With disease progression, the capacity of the plant antioxidant machinery declined, and allowed for ROS accumulation and eventual malondialdehyde production. As for the fungus L. theobromae, the transcripts of genes related to ROS production were significantly repressed, and concomitantly the expression of genes related to antioxidant systems and oxidative stress resistance was markedly upregulated, perhaps to alleviate oxidative stress for successful colonisation. Moreover, genes involved in phytohormones biosynthesis and pathogenesis-related proteins were all markedly promoted, which could contribute to the restriction of disease development in peach shoots. Overall, the results showed that the ROS production-scavenging system in P. persica might affect disease development during peach-L. theobromae interaction. Our findings lay the foundations for future in-depth investigations of the molecular mechanisms and regulatory networks underlying L. theobromae-mediated shoot diseases in terms of ROS production-scavenging systems.