Lipid Remodeling and Signaling in Resistant and Susceptible Oat Cultivars during Powdery Mildew Infection

Lipids play essential roles in both membrane structure and immune regulation in plants. To investigate lipid-based defense mechanisms in oats (Avena sativa) against Blumeria graminis f. sp. avenae (Bga), we conducted integrated lipidomic and transcriptomic analyses on a resistant cultivar (‘Galileo’) and a susceptible one (‘Longyan 2’). ‘Galileo’ showed stronger lipid remodeling and transcriptional responses, including a higher phosphatidylcholine to phosphatidylethanolamine ratio and upregulation of PLA11, PLA15, and PLDδ1. This was accompanied by increased lysophospholipids and FFA(18:3), suggesting enhanced salicylic acid-mediated defense. Although total TAG levels remained stable, polyunsaturated TAG species were enriched in ‘Galileo’, supporting fatty acid buffering and homeostasis. Reductions in MGDG and DGDG, along with differential expression of GDSL lipase genes, further indicated lipid-mediated immune activation. Higher levels of ceramides, phytosphingosine, and cholesteryl esters suggest roles in ROS detoxification and lipid droplet-mediated signaling. These findings underscore lipid remodeling as a key factor in oat resistance to Bga.