The Sterol Methyltransferases SMT1, SMT2, and SMT3 Influence Arabidopsis Development through Nonbrassinosteroid Products
The Sterol Methyltransferases SMT1, SMT2, and SMT3 Influence Arabidopsis Development through Nonbrassinosteroid Products
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DOI：
10.1104/pp.109.152587
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发表时间：
2010-06-01
期刊：
影响因子：
7.4
通讯作者：
Nelson, Timothy
中科院分区：
文献类型：
--
作者：
Carland, Francine;Fujioka, Shozo;Nelson, Timothy
植物甾醇是细胞膜的结构组分，其为膜提供刚性、渗透性和区域特性。类固醇也是油菜素类固醇信号分子的前体。越来越多的证据表明，特定的甾醇在发育过程中的模式形成中发挥作用。CVP 1编码C-24甾醇甲基转移酶2（SMT 2），是拟南芥（Arabidopsis thaliana）的三种SMTs之一。SMT 2和SMT 3也编码C-24 SMT，催化将结构甾醇的合成与信号传导油菜素类固醇衍生物区分开的反应，并且受到高度调节。在cvp 1突变体中SMT 2的缺乏导致中度发育缺陷，包括异常的子叶静脉图案，锯齿状花器官和身材减少，但植物是可行的，这表明SMT 3活性可以替代SMT 2的损失。为了测试SMT 2和SMT 3的不同发育作用，我们鉴定了转录本无效的SMT 3突变体。虽然smt 3单突变体表现为野生型，但cvp 1 smt 3双突变体表现出比cvp 1突变体更强的缺陷，如子叶脉不连续，并产生新的表型，包括根生长缺陷、顶端优势丧失、不育和同源异型花转化。这些表型与特定甾醇的配置文件中的主要变化，但没有显着改变油菜素类固醇配置文件。cvp 1突变体中甾醇谱的改变影响生长素反应，表现为弱的生长素不敏感性，增强axr 1生长素抗性，异位表达DR 5：β-葡萄糖醛酸酶在发育中的胚胎，和缺陷的反应生长素抑制PIN 2-绿色荧光蛋白内吞作用。我们讨论了这些结果所暗示的甾醇的发展作用。
Plant sterols are structural components of cell membranes that provide rigidity, permeability, and regional identity to membranes. Sterols are also the precursors to the brassinosteroid signaling molecules. Evidence is accumulating that specific sterols have roles in pattern formation during development. COTYLEDON VASCULAR PATTERNING1 (CVP1) encodes C-24 STEROL METHYLTRANSFERASE2 (SMT2), one of three SMTs in Arabidopsis (Arabidopsis thaliana). SMT2 and SMT3, which also encodes a C-24 SMT, catalyze the reaction that distinguishes the synthesis of structural sterols from signaling brassinosteroid derivatives and are highly regulated. The deficiency of SMT2 in the cvp1 mutant results in moderate developmental defects, including aberrant cotyledon vein patterning, serrated floral organs, and reduced stature, but plants are viable, suggesting that SMT3 activity can substitute for the loss of SMT2. To test the distinct developmental roles of SMT2 and SMT3, we identified a transcript null smt3 mutant. Although smt3 single mutants appear wild type, cvp1 smt3 double mutants show enhanced defects relative to cvp1 mutants, such as discontinuous cotyledon vein pattern, and produce novel phenotypes, including defective root growth, loss of apical dominance, sterility, and homeotic floral transformations. These phenotypes are correlated with major alterations in the profiles of specific sterols but without significant alterations to brassinosteroid profiles. The alterations to sterol profiles in cvp1 mutants affect auxin response, demonstrated by weak auxin insensitivity, enhanced axr1 auxin resistance, ectopically expressed DR5:beta-glucuronidase in developing embryos, and defective response to auxin-inhibited PIN2-green fluorescent protein endocytosis. We discuss the developmental roles of sterols implied by these results.