MAPK signaling pathway and rhizosphere modulation: mechanisms of arbuscular mycorrhizal symbiosis in enhancing Phragmites communis tolerance to triclocarban stress.

Abstract

With escalating global health challenges, triclocarban (TCC) contamination has reemerged as a critical ecological threat, especially in wetland ecosystems. Yet, the mechanisms by which arbuscular mycorrhizal fungi (AMF) regulate plant root resistance and the rhizosphere environment under TCC exposure remain poorly understood. Here, we established an AMF-Phragmites communis symbiotic system and conducted TCC exposure experiments. Our results demonstrated that TCC exposure significantly inhibited mycorrhizal colonization, root morphology, and the antioxidant system of P. communis. Specifically, under the 5 mg kg^- 1 soil TCC exposure, arbuscule abundance decreased by 3.53-fold, root total length declined to 1011.13 cm, and the integrated biomarker response index value of the antioxidant system dropped to 0.25. In contrast, arbuscular mycorrhizal (AM) symbiosis promoted root morphological and physiological growth. Transcriptome analysis revealed that AM symbiosis upregulated genes encoding key enzymes in the Mitogen-Activated Protein Kinase (MAPK) signaling pathway (e.g., MAPKKK and MAPK family members), whereas TCC exposure downregulated their expressions. Furthermore, in the rhizosphere soil, the composition and structure of microbial communities were distinctly influenced by AM symbiosis and TCC exposure. Compared to AM symbiosis, which upregulated soil metabolites associated with metabolism, TCC exposure downregulated soil metabolites across multiple functional categories, including metabolism, environmental information processing, and cellular processes. This research broadens our understanding of how AM symbiosis enhances the resistance of P. communis and maintains the stability of the rhizosphere environment under TCC exposure, and evidences the potential of AMF application in improving the purification capacity of wetland systems.