Brassinosteroid/sterol synthesis and plant growth as affected by Ika and Ikb mutations of pea
Brassinosteroid/sterol synthesis and plant growth as affected by Ika and Ikb mutations of pea
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DOI：
10.1104/pp.119.4.1517
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发表时间：
1999-04-01
期刊：
影响因子：
7.4
通讯作者：
Yokota, T
中科院分区：
文献类型：
--
作者：
Nomura, T;Kitasaka, Y;Yokota, T
矮豌豆 (Pisum sativum) 突变体 Ika 和 Ikb 分别对油菜素类固醇 (BR) 不敏感和缺乏。通过外源应用油菜素内酯及其生物合成前体，Ikb突变体的矮化表型被恢复为野生型。对该突变体中内源甾醇的气相色谱-质谱分析表明，它积累了24-亚甲基胆固醇和异岩藻甾醇，但缺乏它们的氢化产物菜油甾醇和谷甾醇。使用H-2标记的24-亚甲基胆固醇的喂养实验表明lkb突变体不能异构化和/或还原Delta(24(28))双键。因此，Ikb 突变体的侏儒症是由于 24 亚甲基胆固醇合成菜油甾醇受阻而引起的 BR 缺陷所致。 Ikb突变还破坏了膜的甾醇组成，与野生型相比，其含有异岩藻甾醇作为主要甾醇并且缺乏豆甾醇。 Ika 突变体并不缺乏 BR，因为它积累了卡斯特酮。与一些对赤霉素不敏感的矮化突变体一样，Ika 突变体中卡斯特酮的过量产生可能归因于由于 BR 的感知/信号转导受损而缺乏反馈控制机制。讨论了卡斯特酮是一种具有生物活性的 BR 的可能性。
The dwarf pea (Pisum sativum) mutants Ika and Ikb are brassinosteroid (BR) insensitive and deficient, respectively. The dwarf phenotype of the Ikb mutant was rescued to wild type by exogenous application of brassinolide and its biosynthetic precursors. Gas chromatography-mass spectrometry analysis of the endogenous sterols in this mutant revealed that it accumulates 24-methylenecholesterol and isofucosterol but is deficient in their hydrogenated products, campesterol and sitosterol. Feeding experiments using H-2-labeled 24-methylenecholesterol indicated that the lkb mutant is unable to isomerize,and/or reduce the Delta(24(28)) double bond. Dwarfism of the Ikb mutant is, therefore, due to BR deficiency caused by blocked synthesis of campesterol from 24methylenecholesterol. The Ikb mutation also disrupted sterol composition of the membranes, which, in contrast to those of the wild type, contained isofucosterol as the major sterol and lacked stigmasterol. The Ika mutant was not BR deficient, because it accumulated castasterone. Like some gibberellin-insensitive dwarf mutants, overproduction of castasterone in the Ika mutant may be ascribed to the lack of a feedback control mechanism due to impaired perception/signal transduction of BRs. The possibility that castasterone is a biologically active BR is discussed.