title: Development of low phytate rice by RNAi mediated seed-specific silencing of inositol 1,3,4,5,6-pentakisphosphate 2-kinase gene (IPK1).
abstract: 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.
authors.affiliation: Plant Molecular Biology and Biotechnology Laboratory, Department of Botany, University of Calcutta, Kolkata, West Bengal, India.
authors.forename: Nusrat
authors.initials: N
authors.lastname: Ali
authors.forename: Soumitra
authors.initials: S
authors.lastname: Paul
authors.forename: Dipak
authors.initials: D
authors.lastname: Gayen
authors.forename: Sailendra Nath
authors.initials: SN
authors.lastname: Sarkar
authors.forename: Karabi
authors.initials: K
authors.lastname: Datta
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Datta
mesh_terms: D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics; D007294:Inositol / Q000378:metabolism; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D010710:Phosphates; D007294:Inositol; D010833:Phytic Acid; D017853:Phosphotransferases (Alcohol Group Acceptor); C502806:inositol 1,3,4,5,6-pentakisphosphate 2-kinase