Plant Molecular Biology and Biotechnology Laboratory, Department of Botany, University of Calcutta, Kolkata, West Bengal, India.
PLoS One. 2013 Jul 2;8(7):e68161. doi: 10.1371/journal.pone.0068161. Print 2013.
Phytic acid (InsP(6)) is considered to be the major source of phosphorus and inositol phosphates in most cereal grains. However, InsP(6) is not utilized efficiently by monogastric animals due to lack of phytase enzyme. Furthermore, due to its ability to chelate mineral cations, phytic acid is considered to be an antinutrient that renders these minerals unavailable for absorption. In view of these facts, reducing the phytic acid content in cereal grains is a desired goal for the genetic improvement of several crops. In the present study, we report the RNAi-mediated seed-specific silencing (using the Oleosin18 promoter) of the IPK1 gene, which catalyzes the last step of phytic acid biosynthesis in rice. The presence of the transgene cassette in the resulting transgenic plants was confirmed by molecular analysis, indicating the stable integration of the transgene. The subsequent T4 transgenic seeds revealed 3.85-fold down-regulation in IPK1 transcripts, which correlated to a significant reduction in phytate levels and a concomitant increase in the amount of inorganic phosphate (Pi). The low-phytate rice seeds also accumulated 1.8-fold more iron in the endosperm due to the decreased phytic acid levels. No negative effects were observed on seed germination or in any of the agronomic traits examined. The results provide evidence that silencing of IPK1 gene can mediate a substantial reduction in seed phytate levels without hampering the growth and development of transgenic rice plants.
植酸（InsP(6)）被认为是大多数谷物中磷和肌醇磷酸盐的主要来源。然而，由于缺乏植酸酶，单胃动物不能有效地利用 InsP(6)。此外，由于其螯合矿物质阳离子的能力，植酸被认为是一种抗营养物质，使这些矿物质无法被吸收。鉴于这些事实，降低谷物中的植酸含量是几种作物遗传改良的理想目标。在本研究中，我们报告了利用 Oleosin18 启动子进行的 RNAi 介导的种子特异性沉默（seed-specific silencing）IPK1 基因，该基因催化水稻中植酸生物合成的最后一步。转基因植物中存在转基因盒的情况通过分子分析得到证实，表明转基因的稳定整合。随后的 T4 转基因种子显示 IPK1 转录物的表达下调了 3.85 倍，这与植酸盐水平的显著降低以及无机磷酸盐（Pi）含量的相应增加相关。由于植酸水平降低，低植酸水稻种子在胚乳中也积累了 1.8 倍的铁。在种子发芽或任何检查的农艺性状方面均未观察到负面影响。结果表明，沉默 IPK1 基因可以介导种子植酸盐水平的显著降低，而不会阻碍转基因水稻植物的生长和发育。
