RNAi-INDUCED TRANSCRIPTIONAL SILENCING OF INOSITOL POLYPHOSPHATE 6-/3-/5-KINASE (IPK2) GENE IN SOYBEAN SEEDS TO GENERATE LOW PHYTATE LINES

Abstract

Soybean is one of the leading oilseed crops in the world and is showing a remarkable surge in its utilization in formulating animal feeds and supplements. Its dietary consumption, however, is incongruent with its existing industrial demand due to the presence of anti-nutritional factors in sufficiently large amounts. Phytic acid, in particular, raises concern as it causes a concomitant loss of indigestible complexed minerals and charged proteins in the waste and results in reduced mineral bioavailability in both livestock and humans. Reducing the seed phytate level thus seems indispensable to overcome the nutritional menace associated with soy grain consumption. To conceive our objective, we designed and expressed an inositol poly phosphate 6-/3-/5-kinase gene-specific intron-containing self-complementary hairpin RNAi construct in the seeds of Pusa-16 soybean cultivar. Inositol polyphosphate 6-/3 /5-kinase is a multifunctional kinase which catalyzes the formation of inositol pentakisphosphate, the immediate substrate of PA biosynthesis. Due to a broad range of substrate specificity, it plays a pivotal role in regulating the cellular phytic acid turnover and is therefore conceived to be the most appropriate target for effective seed phytate reduction. We subsequently conducted a genotypic, phenotypic, and biochemical analysis of the developed putative transgenic populations and found low phytic acid levels, moderate accumulation of inorganic phosphate and elevated mineral content in some lines. These low phytic acid lines did not show any reduction in seedling emergence and displayed an overall good agronomic performance, thus, proving to be a successful attempt.