Proposed Dual Mechanisms of Arbuscular Mycorrhizal Fungi in Enhancing Soybean Resistance to Continuous Cropping via the LACS8-Palmitoleic Acid Axis.

Abstract

Intensive soybean (Glycine max L.) production is severely constrained by continuous cropping obstacles, which induce root oxidative stress and lipid peroxidation. These processes compromise cell membrane integrity, inhibiting plant development, and ultimately reducing yield and quality. This study investigated whether the alleviation of continuous cropping obstacles by arbuscular mycorrhizal fungi (AMF) was associated with fatty acid synthesis and root membrane lipid systems. Through Funneliformis mosseae (F. mosseae)-inoculated pot experiments, we integrated physiological, transcriptomic, proteomic, and metabolomic analyses to investigate the effects of AMF inoculation on fatty acid synthesis and root membrane lipid systems in soybean roots. Results showed that F. mosseae inoculation effectively mitigated membrane lipid peroxidation and promoted growth. Specifically, it significantly increased plant height, root metabolic activity, and superoxide dismutase (SOD) activity by 21.23%, 49.34%, and 46.17%, respectively. Conversely, hydrogen peroxide (H₂O₂) content, lipoxygenase (LOX) activity, and malondialdehyde (MDA) content decreased by 34.88%, 25.82%, and 47.83%, respectively. Furthermore, LACS8 upregulation was associated with fatty acid biosynthesis and palmitoleic acid accumulation in F. mosseae-inoculated plants. In summary, these results suggest a dual protective mechanism involving structural membrane repair and antioxidant defense, associated with the LACS8-palmitoleic acid pathway, and potentially related to the alleviation of soybean continuous cropping obstacles. This multi-omics study provides new insights into the potential role of fatty acid biosynthesis in soybean adaptation to continuous cropping under AMF inoculation. These findings deepen the understanding of AMF-plant stress resistance and support utilizing AMF inoculants for sustainable soybean production.