White leaf spot in maize (WLS) severely threatens maize yield and quality. Risk assessment suggests that it may become one of the most significant maize diseases in China. Exogenous arachidonic acid offers a novel strategy for enhancing crop stress resistance. This study aims to investigate the effects and mechanisms of ARA in inducing resistance against WLS. The study found that 15 µM ARA effectively induces systemic resistance in maize against WLS. This resistance manifests as a multi-layered synergistic defense response. ARA treatment protected the photosynthetic performance of the leaves, primarily by maintaining the photosynthetic area, maximum photochemical efficiency, and photoprotective capacity (NPQ) of the infected leaves, thereby ensuring the supply of energy and carbon skeletons. Additionally, ARA treatment significantly enhanced the phenylalanine metabolic pathway, increasing the activity of key defense enzymes, including phenylalanine ammonia-lyase (PAL), chitinase (CHI), peroxidase (POD), and laccase (LAC). This drove the accumulation of disease resistance-related compounds such as lignin, coumarins, and flavonoids, thereby strengthening both physical and chemical barriers. Furthermore, ARA treatment reduced the accumulation of malondialdehyde (MDA), a product of membrane lipid peroxidation, and reducing sugars, indicating alleviated cellular oxidative damage and improved carbon metabolism balance. Metabolomic analysis further confirmed the critical role of phenylalanine metabolism. This study demonstrates that exogenous ARA application does not merely trigger an isolated response but initiates an integrated disease resistance program, coordinating multiple processes such as photosynthetic protection, cell wall reinforcement, and the accumulation of antimicrobial compounds. Based on the experimental results, we speculate that this systemically enhanced resistance may be closely associated with the activation of the salicylic acid signaling pathway. These findings not only provide a theoretical foundation for utilizing ARA as an eco-friendly plant resistance inducer to control WLS, but also offer novel biological insights into how endogenous signaling networks integrate multiple defense layers, thereby contributing to the advancement of sustainable agriculture.
Xia et al. (Mon,) studied this question.