Abstract
Phytic acid (InsP6) is considered to be the major source of phosphorus and inositol phosphates in most cereal grains. However, InsP6 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.
Highlights
Phytic acid is known as the major source of phosphorus in cereal grains, comprising approximately 1–2% of the dry weight and accounting for approximately 65–80% of the total seed phosphorus [1]
We demonstrated the efficient down-regulation of phytic acid, as mediated by silencing of the IPK1 gene, the product of which catalyzes the last step of the phytate biosynthesis
In Arabidopsis, a T-DNA disruption of the gene for InsP5 2-kinase has been reported to have resulted in an 83% decrease in phytic acid levels [28]
Summary
Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate or IP6) is known as the major source of phosphorus in cereal grains, comprising approximately 1–2% of the dry weight and accounting for approximately 65–80% of the total seed phosphorus [1]. During the process of germination, endogenous grain phytase is activated, which degrades phytate, releasing stored phosphorus, myo-inositol and bound mineral cations [1] that are further utilized by the developing seedlings. Phytate has six negatively charged ions, making it a potent chelator of such divalent cations as Fe2+, Zn2+, Ca2+, and Mg2+ and rendering these ions unavailable for absorption by monogastric animals [4]. In view of these adverse effects, many attempts have been made to reduce the phytic acid content in cereals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
