Maillot-Vernier P, Gondet L, Schaller H, Benveniste P, Belliard G
Laboratoire de Génétique Physiologique IBMC-CNRS, Strasbourg, France.
Mol Gen Genet. 1991 Dec;231(1):33-40. doi: 10.1007/BF00293818.
A genetic and biochemical characterization is presented of a tobacco mutant that was previously shown to have an increased sterol content with an accumulation of biosynthetic intermediates. We first show that a precise regulation of the membrane sterol composition occurs in this mutant, via a selective esterification process. Indeed, sterols representing the usual end-products of the biosynthetic pathway are preferably integrated into the membranes as free sterols, whereas most of the intermediates pool is esterified and stored in cytoplasmic lipid droplets. It is further demonstrated that overproduction of sterols by the LAB1-4 mutant is due to a single nuclear and semi-dominant mutation. Finally, increase of biosynthesis and esterification of unusual sterols are shown to be responsible for the resistance of LAB1-4 calli to LAB170 250F, the triazole pesticide used to select this mutant. However, differentiated LAB1-4 tissues do not express the resistance trait, suggesting that sterol biosynthesis might not be the only site of action for the triazole at the plant level.
本文介绍了一种烟草突变体的遗传和生化特征，该突变体先前已被证明具有较高的甾醇含量，并积累了生物合成中间体。我们首先表明，通过选择性酯化过程，该突变体中膜甾醇组成存在精确调控。实际上，代表生物合成途径常见终产物的甾醇更倾向于以游离甾醇的形式整合到膜中，而大部分中间体池则被酯化并储存在细胞质脂滴中。进一步证明，LAB1 - 4突变体中甾醇的过量产生是由于单个核基因且半显性突变所致。最后，研究表明不寻常甾醇生物合成和酯化的增加是LAB1 - 4愈伤组织对用于筛选该突变体的三唑类农药LAB170 250F产生抗性的原因。然而，分化的LAB1 - 4组织不表现出抗性特征，这表明甾醇生物合成可能不是三唑类农药在植物水平上的唯一作用位点。
