A Low-Phytate Soybean Line Disturbs Seed Development-Dependent mRNA Splicing in the Phytate synthesis gene inositol-1,3,4 trisphosphate 5/6-kinase (GmITPK3)

Low-phytate (LP) crops may improve the mineral bioavailability in monogastric animals, which will serve to decrease phosphate pollution. Recently, we reported a newly developed LP soybean line with normal emergence, growth, and yield when compared to the Natto-kotsubu (Natto) cultivar as well as lower phytic acid content than the CX1834 line. However, the mechanism underlying the reduced levels of phytic acid (InsP6) in this LP line requires further elucidation. In this study, an intron retention (IR) event was detected in inositol-1,3,4 trisphosphate 5/6-kinase 3 (GmITPK3) in Natto, normal-phytate (NP) and LP leaves. The abundance of each IR transcripts (IRTs) was changed during seeds development may maintain the phytic acid level in Natto cultivar, however, the abundant of IRTs produced in LP line may perturb the phosphorylation of InsP4 to InsP5 and/or create a negative feedback effect on InsP4 and InsP3 synthesis, leading to reduced phytic acid levels in the LP line during seed development. Hence, the GmITPK3 mutant might involve the decrease the level of phytic acid in seeds without harming the plants, thus representing a new strategy for LP crop development.