Brassinosteroid-induced changes of lipid composition in leaves of Pisum sativum L. during senescence.

The effect of steroid phytohormone 24-epibrassinolide (EBR) on the composition of some lipid classes (free fatty acids, triacylglycerols and galactolipids) in detached pea leaves was studied for the first time. EBR (0.1μM) promoted senescence and increased the content of 14:0, 16:0 and 18:1 free fatty acids as well as 18:2 and 18:3 bound to triacylglycerols in the detached leaves in contrast to mock-treated leaves. The content of all identified fatty acids bound to galactolipids decreased in the detached leaves treated with EBR compared to that in mock-treated leaves. These findings suggest that free fatty acids are liberated from polar lipids and then undergo esterification to neutral lipids in the detached leaves upon EBR treatment. We propose that steroid phytohormones may be involved into regulation of leaf senescence via alteration of cell lipid composition.