Plant Coumarin\nMetabolism–Microbe Interactions:\nAn Effective Strategy for Reducing Imidacloprid Residues and Enhancing\nthe Nutritional Quality of Pepper

Imidacloprid\n(IMI) stress positively correlates with the potential\nof coumarins to alleviate abiotic stress. However, little is known\nabout the pathways and mechanisms by which coumarin reduces the IMI\nresidue by regulating plant secondary metabolism and plant–microbe\ninteractions. This study examined the impact of coumarin on the uptake,\ntranslocation, and metabolism of IMI in pepper plants by modulating\nthe signal molecule levels and microbial communities in the rhizosphere\nand phyllosphere. Analysis of 2 h28 d pesticide residue dynamics\nrevealed that coumarin dramatically reduced IMI concentration in pepper\nfruits. Coumarin upregulated the phenylpropane pathway genes, which\nincreased the levels of flavonoids, phenolic acids, phytohormones,\nand capsaicinoids. Importantly, phyllosphere and rhizosphere microbial\ndiversity results showed that coumarin improved the abundance of beneficial\nmicroorganisms and positively correlated with secondary metabolite\nsecretion. Therefore, coumarin exploited the interaction between the\nphenylpropane and coumarin synthesis pathways and beneficial microbes\nto enhance the nutritional quality and IMI degradation.