AM Fungi Alleviate Soybean Continuous Cropping Obstacles by Regulating Root Phenylpropanoid Biosynthesis Pathway

Continuous soybean cropping degrades soil quality and promotes pathogen accumulation, thereby restricting plant growth and reducing yield and quality. Arbuscular mycorrhizal fungi (AMF) enhance plant resistance to various stressors. This study investigates the role of phenylpropanoid biosynthesis in soybean roots in overcoming the challenges of continuous cropping, leveraging AMF's stress resistance properties from genetic and proteomic perspectives. A combined transcriptomic and proteomic analysis of soybean roots, along with phenotypic assessments, was conducted to elucidate AMF-mediated regulation of phenylpropanoid biosynthesis in mitigating continuous cropping stress. The results showed that AMF inoculation under continuous cropping conditions increased soluble protein content and root vitality, promoting plant height, fresh weight, and dry weight. Both continuous cropping and AMF inoculation influenced the expression of genes and proteins involved in phenylpropanoid biosynthesis in soybean roots. Continuous cropping suppressed genes such as pnc1 and Glyma.09G284700 and proteins including peroxidase, β-glucosidase. In contrast, AMF inoculation upregulated genes such as 4cll7, pnc1, and prxc3, along with proteins such as PAL, PRXC3, PER54, BGLU44.1, BGLU44.2, and CYP73A11, thereby alleviating continuous cropping stress and promoting soybean growth. Therefore, this study demonstrates that AMF mitigates continuous cropping stress by enhancing phenylpropanoid biosynthesis in soybean roots, providing theoretical and practical insights for sustainable soybean production.