Inhibition of Sterol Biosynthesis and Stem Elongation of Tobacco Seedlings Induced by Some Hypocholesterolemic Agents

Abstract

Incorporation of DL-[2-¹⁴C]mevalonic acid ([2-¹⁴C]MVA) into 4-desmethylsterols in Nicotiana tabacum cv. Turkish Samson seedlings was inhibited by SK&F 7997-A₃,¹ SK&F 7732-A₃, AY 9944, and the plant growth retardant, Amo 1618. Reductions in 4-desmethylsterol levels resulted from treatment with AY 9944 and Amo 1618, but not the SK&F compounds. Amo 1618 and SK&F 7997-A₃ both significantly reduced the specific activity of each of the four major 4-desmethylsterols examined. Although SK&F 7732-A₃ reduced the specific activity of campesterol, and AY 9944 reduced the specific activity of stigmasterol, neither had an effect on the specific activity of β-sitosterol. Stem elongation of tobacco seedlings was retarded by SK&F 7997-A₃, AY 9944, and SK&F 7732-A₃, particularly the former, and the retarded plants thus produced were morphologically indistinguishable from the Amo 1618-treated plants. Application of exogenous stigmasterol, or GA₃, to the chemically-retarded plants resulted in a reversal of stem growth retardation.