Phospholipid metabolism in roots and microsomes of sunflower seedlings: Inhibition of choline phosphotransferase activity by boron

Abstract

The action of boron on phospholipid composition and synthesis in roots and microsomes from sunflower seedlings has been studied. The fatty acid composition and relative amounts of individual molecular species of phospholipids in roots and microsomes were very similar. In both the content of phospholipids was decreased and the relative levels of their component fatty acids changed by treatment with 50 ppm of boron. This concentration of boron in the culture medium was found to inhibit the in vivo [1- 14C] acetate incorporation into root lipids and that of [Me- 14C] choline into phosphatidylcholine of root microsomes. Cytidine-5-diphospho (CDP)-[Me- 14C] choline incorporation into phosphatidylcholine of isolated microsomes was also inhibited by 50 ppm of boron when present in the growth medium of seedlings. These results indicate that the decrease in phosphatidylcholine labelling from [ 14C] choline observed when root microsomes were treated with boron would be caused by a decrease in CDP-choline phosphotransferase activity.