RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content, Alters Transcripts of Phytic Acid Biosynthetic Genes, and Modulates Mineral Distribution in Rice Seeds

• Published in: Rice science Vol. 27; no. 4; pp. 315 - 328
• Main Authors: Karmakar, Aritra, Bhattacharya, Sananda, Sengupta, Shinjini, Ali, Nusrat, Sarkar, Sailendra Nath, Datta, Karabi, Datta, Swapan K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2020; Plant Nutrition Department,Centre Mondial de I’Innovation Roullier,Saint Malo 35400,France; Laboratory of Translational Research on Transgenic Crops,Department of Botany,University of Calcutta,Kolkata 700019,West Bengal,India%Laboratory of Translational Research on Transgenic Crops,Department of Botany,University of Calcutta,Kolkata 700019,West Bengal,India; Elsevier
• Subjects: inositol triphosphate kinase-1; mineral content; phytic acid; RNA interference silencing; X-ray microfluorescence; phytic acid; X-ray microfluorescence; mineral content; RNA interference silencing; inositol triphosphate kinase-1
• ISSN: 1672-6308; 1876-4762
• DOI: 10.1016/j.rsci.2020.05.007

Phytic acid is the principal storage form of phosphorus in plant seeds and an essential signalling molecule in several regulatory processes of plant development. However, it is known as an anti-nutrient compound owing to its potent chelating property. Thus, reducing the phytic acid content in crops is desirable. Studies involving regulation of MIPS and IPK1 genes to generate low phytate rice have been reported earlier. However, the functional significance of OsITPK and the effect of its down-regulation on phytic acid content and the associated pleiotropic effects on rice have not yet been investigated. In this study, tissue specific RNA interference (RNAi)-mediated down-regulation of a major ITPK homolog (OsITP5/6K-1) resulted in 46.2% decrease in phytic acid content of T2 transgenic seeds with a subsequent 3-fold enhancement in the inorganic phosphorus content. Silencing of OsITP5/6K-1 altered the transcript levels of essential phytic acid pathway genes, without significantly affecting the transcript levels of other OsITPK homologs. Furthermore, the mapping of elements through X-ray microfluorescence analysis revealed significant changes in the spatial distribution pattern and translocation of elements in low phytate seeds. Additionally, low phytate polished seeds exhibited 1.3-fold and 1.6-fold enhancement in iron and zinc content in the grain endosperm, respectively. Silencing of OsITP5/6K-1 also altered the amino acid and myo-inositol content of the transgenic seeds. Our results successfully established that RNAi-mediated silencing of OsITP5/6K-1 gene significantly reduced the phytate levels in seeds without hampering the germination potential of seeds and plant growth. The present study provided an insight into the mechanism of phytic acid biosynthesis pathway.