Exposure to polyethylene terephthalate microplastics induces reprogramming of flavonoids metabolism and gene regulatory networks in Capsicum annuum

Micro/Nano-plastics (M/NPs) have emerged as a globally concerning pollutant. However, research on the phytotoxicity of M/NPs on plant secondary metabolism and the underlying molecular mechanisms is still limited. Pepper, a widely cultivated vegetable, is rich in flavonoids, which are a class of important secondary metabolites found throughout the plant kingdom with multiple biological functions. In this study, we conducted a detailed assessment of the physiological toxicity of Polyethylene Terephthalate microplastics (PET-MPs) on the growth of pepper seedlings. Results showed that PET-MPs significantly inhibited pepper growth, particularly root development. Moreover, PET-MPs exposure resulted in a burst of ROS, causing oxidative damage. KEGG pathways analysis illustrated that PET-MPs significantly altered the flavonoid biosynthesis and phenylpropanoid biosynthesis pathways at both the metabolome and transcriptome levels. Weighted gene correlation network analysis (WGCNA) identified ten structural genes and nine transcription factor genes that play pivotal roles in regulating flavonoid biosynthesis. In summary, this study elucidates the alterations in the flavonoid composition, along with the underlying gene regulatory network governing flavonoid metabolism under PET-MPs exposure in pepper. These findings enhance our comprehension of MPs pollution and provide valuable insights for the development of sustainable agro-ecosystems and food security in the future.