RNAi mediated down regulation of myo-inositol-3-phosphate synthase to generate low phytate rice.
RNAi mediated down regulation of myo-inositol-3-phosphate synthase to generate low phytate rice.
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DOI：
10.1186/1939-8433-6-12
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发表时间：
2013-05-15
期刊：
影响因子：
--
通讯作者：
Datta K
中科院分区：
文献类型：
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作者：
Ali N;Paul S;Gayen D;Sarkar SN;Datta SK;Datta K
植酸（InsP 6）被认为是谷物中磷和肌醇磷酸的主要来源。鉴于其抗营养素特性，降低谷物中的植酸水平是期望的，以最大限度地提高矿物质生物利用度并最小化磷废物管理的负荷。我们在这里报告RNAi介导的种子特异性沉默肌醇-3-磷酸合成酶（MIPS）基因催化的植酸生物合成的第一步。此外，我们还研究了MIPS沉默对肌醇及其相关代谢的可能影响，因为植酸生物合成的第一步也是MIPS催化的肌醇合成的限速步骤。得到的转基因水稻植株（T3）显示MIPS基因表达下调4.59倍，这对应于种子中植酸水平的显著降低和无机磷酸盐量的同时增加。转基因植株的肌醇含量也减少，这是由于植酸生物合成途径的第一步被破坏，这进一步降低了抗坏血酸的水平并改变了转基因植株对脱落酸（阿坝）的敏感性。此外，我们的研究结果表明，在转基因植物中，较低的植酸水平导致二价阳离子的增加，其中1.6倍的铁浓度增加在精米种子是值得注意的。这种增加可能是由于减少螯合二价金属（铁）阳离子，这可能与较高的铁生物利用度在水稻籽粒胚乳。本研究表明，种子特异性沉默转基因水稻植株中的MIPS可以产生植酸水平的显著降低，沿着无机磷含量的增加。然而，也证明了低植酸盐种子具有不期望的肌醇和抗坏血酸盐水平的减少，这可能导致种子在萌发期间对脱落酸的敏感性。因此，这表明，虽然MIPS是产生低植酸转基因植物的主要目标，MIPS的下调可能会对肌醇合成和参与关键植物代谢的相关途径产生不利影响。本文的在线版本（doi：10.1186/1939-8433-6-12）包含补充材料，可供授权用户使用。
Phytic acid (InsP6) is considered as the major source of phosphorus and inositol phosphates in cereal grains. Reduction of phytic acid level in cereal grains is desirable in view of its antinutrient properties to maximize mineral bioavailability and minimize the load of phosphorus waste management. We report here RNAi mediated seed-specific silencing of myo-inositol-3-phosphate synthase (MIPS) gene catalyzing the first step of phytic acid biosynthesis in rice. Moreover, we also studied the possible implications of MIPS silencing on myo-inositol and related metabolism, since, first step of phytic acid biosynthesis is also the rate limiting step of myo-inositol synthesis, catalyzed by MIPS. The resulting transgenic rice plants (T3) showed a 4.59 fold down regulation in MIPS gene expression, which corresponds to a significant decrease in phytate levels and a simultaneous increment in the amount of inorganic phosphate in the seeds. A diminution in the myo-inositol content of transgenic plants was also observed due to disruption of the first step of phytic acid biosynthetic pathway, which further reduced the level of ascorbate and altered abscisic acid (ABA) sensitivity of the transgenic plants. In addition, our results shows that in the transgenic plants, the lower phytate levels has led to an increment of divalent cations, of which a 1.6 fold increase in the iron concentration in milled rice seeds was noteworthy. This increase could be attributed to reduced chelation of divalent metal (iron) cations, which may correlate to higher iron bioavailability in the endosperm of rice grains. The present study evidently suggests that seed-specific silencing of MIPS in transgenic rice plants can yield substantial reduction in levels of phytic acid along with an increase in inorganic phosphate content. However, it was also demonstrated that the low phytate seeds had an undesirable diminution in levels of myo-inositol and ascorbate, which probably led to sensitiveness of seeds to abscisic acid during germination. Therefore, it is suggested that though MIPS is the prime target for generation of low phytate transgenic plants, down-regulation of MIPS can have detrimental effect on myo-inositol synthesis and related pathways which are involved in key plant metabolism. The online version of this article (doi:10.1186/1939-8433-6-12) contains supplementary material, which is available to authorized users.