Functional analysis of three peroxisomal cinnamate:CoA ligases in salicylic acid biosynthesis of Glycine max.

Salicylic acid (SA), a phenolic-derived secondary metabolite, serves as a critical signaling molecule in plant defense mechanisms. Contemporary phytochemical studies have identified two distinct biosynthetic pathways for SA production in plants: the isochorismate synthase (ICS)-mediated pathway and the phenylalanine ammonia-lyase (PAL)-dependent pathway. However, the enzymes participating in SA biosynthesis in soybean remain largely unknown. Here, we identified three peroxisomal Glycine max cinnamate:CoA ligases (GmCNLs) that are required for SA biosynthesis, and further validated their roles through Bean pod mottle virus (BPMV)-induced gene silencing experiments, which showed that silencing these three GmCNL genes significantly reduced SA content in soybean, thereby weakening soybean disease resistance to Xanthomonas axonopodis pv. glycine (Xag). Furthermore, this study indicates that GmCNL2 may play a major role in the PAL pathway-derived SA biosynthesis in response to pathogen infection. We further elucidated the key step in the process of PAL pathway-mediated SA biosynthesis in soybean and provided valuable insights into the potential for enhancing soybean disease resistance through the manipulation of GmCNLs expression.