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.