Overexpression of CYP710A1 and CYP710A4 in transgenic Arabidopsis plants increases the level of stigmasterol at the expense of sitosterol
Overexpression of CYP710A1 and CYP710A4 in transgenic Arabidopsis plants increases the level of stigmasterol at the expense of sitosterol
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DOI：
10.1007/s00425-007-0618-8
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发表时间：
2008-01-01
期刊：
影响因子：
4.3
通讯作者：
Sitbon, Folke
中科院分区：
文献类型：
--
作者：
Arnqvist, Lisa;Persson, Mattias;Sitbon, Folke
谷甾醇和豆甾醇是维管束植物中的主要甾醇。改变豆甾醇和谷甾醇的比例可以影响细胞膜的性质，特别是在不同的胁迫下，但对豆甾醇的生物合成知之甚少。然而，最近，Morikawa等人。植物细胞18：1008-1022,2006)在拟南芥中发现，豆甾醇和油菜籽甾醇的合成是由两个独立的甾醇C-22去饱和酶催化的，分别由基因CYP710A1和CYP710A2编码。这些蛋白属于一个小的细胞色素P450亚家族，有四个成员，命名为CYP710A1-A4，与参与麦角固醇合成的酵母甾醇C-22去饱和酶Erg5p有关。在这里，我们报告了我们对拟南芥CYP710A家族的平行研究。为了阐明细胞色素P710A蛋白的功能，获得了高表达细胞色素P710A1和细胞色素P710A4的转基因拟南芥植株。与野生型植株相比，两种类型的转化子都表现出正常的表型，但含有较高水平的游离豆甾醇和较低水平的游离谷甾醇。CYP710A1转化子还显示出更高水平的豆甾醇、胆固醇、24-甲基胆固醇和异胡萝卜醇的酯化形式。结果证实了Morikawa等人的发现。(植物细胞18：1008-1022,2006)关于细胞色素P710A1在豆甾醇合成中的功能的研究，并表明细胞色素P710A4也具有这一功能。此外，我们的结果表明，增加豆甾醇水平本身就足以刺激其他主要甾醇的酯化。
Sitosterol and stigmasterol are major sterols in vascular plants. An altered stigmasterol:sitosterol ratio has been proposed to influence the properties of cell membranes, particularly in relation to various stresses, but biosynthesis of stigmasterol is poorly understood. Recently, however, Morikawa et al. (Plant Cell 18:1008-1022, 2006) showed in Arabidopsis thaliana that synthesis of stigmasterol and brassicasterol is catalyzed by two separate sterol C-22 desaturases, encoded by the genes CYP710A1 and CYP710A2, respectively. The proteins belong to a small cytochrome P450 subfamily having four members, denoted by CYP710A1-A4, and are related to the yeast sterol C-22 desaturase Erg5p acting in ergosterol synthesis. Here, we report on our parallel investigation of the Arabidopsis CYP710A family. To elucidate the function of CYP710A proteins, transgenic Arabidopsis plants were generated overexpressing CYP710A1 and CYP710A4. Compared to wild-type plants, both types of transformant displayed a normal phenotype, but contained increased levels of free stigmasterol and a concomitant decrease in the level of free sitosterol. CYP710A1 transformants also displayed higher levels of esterified forms of stigmasterol, cholesterol, 24-methylcholesterol and isofucosterol. The results confirm the findings of Morikawa et al. (Plant Cell 18:1008-1022, 2006) regarding the function of CYP710A1 in stigmasterol synthesis, and show that CYP710A4 also has this capacity. Furthermore, our results suggest that an increased stigmasterol level alone is sufficient to stimulate esterification of other major sterols.