Accumulation of Rare Phytosterols in Plant Cells on Treatment with Metabolic Inhibitors and Mevalonic Acid

Abstract

Root application of the metabolic inhibitors D-ethionine (100 μm) and L-ethionine (30 μm), which were expected to inhibit alkylation of the sterol side chains, merely reduced the sterol content in the roots of Medicago sativa seedlings. The major sterol was stigmasterol. However, when (3RS)-mevalonic acid (2 mm) was applied together with ethionine, cydoartenol (about 50% of the total sterols) accumulated in the roots. The hypocotyls of the ethionine-treated seedlings accumulated cholesterol (34% of the total sterols), and mevalonic acid showed no additional effect in this case.

In a suspension culture of Nicotiana tabacum, the most abundant sterol was campesterol. When cells were treated with buthiobate (100 μm), a potent inhibitor of lanosterol 14α-demethylation in yeasts and fungi, obtusifoliol accumulated in the treated cells (50% of the total sterols). 14α-Methylfecosterol also accumulated in the treated cells. The addition of mevalonic acid (1 mm together with buthiobate increased the obtusifoliol content (63% of the total sterols).