Characterization of Phospholipase D from Arabidopsis thaliana Callus in Response to Ent-Kaurene Diterpenoid Leukamenin E

Abstract

A variety of components have been isolated from various higher plants and characterized as allelochemicals, which can play an important role in natural plant communities. Leukamenin E is an ent-kaurene diterpenoid isolated from Isodon racemosa (Hemsl) Hara. Phospholipase D (PLD) is a key enzyme involved in membrane phospholipid catabolism during plant growth, development, and stress responses. To further explore and elaborate the responses of PLD to leukamenin E treatment, the activities and expression patterns of the PLD gene in Arabidopsis thaliana (A. thaliana) callus were researched. When A. thaliana callus was incubated with leukamenin E at concentrations of 100 and 200 μM for 48 h, the activities of PLD in microsomal and mitochondrial membranes exhibited an upregulation behavior, with the highest levels at 24 and 36 h, respectively. RT-PCR analyses suggested that PLD activity partially corresponded to the A. thaliana PLD gene transcript level. As indicators of membrane damage, electrolyte leakage and malondialdehyde contents increased significantly and peaked at hour 36 and then decreased when A. thaliana callus was treated by leukamenin E. The contents of osmotic adjustment components proline and soluble sugar also shared similar trends. These results demonstrated that the specific mechanism of the A. thaliana response to leukamenin E was linked to PLD.