Characterization of the TaMIPS gene from winter wheat (Triticum aestivum L.) and changes in its expression pattern with phytic acid accumulation in seeds during grain filling

D-myo-Inositol-3-phosphate (D-Ins(3)P1) synthase (MIPS EC 5.5.1.4) catalyzes the first step in the phytic acid biosynthetic pathway. To understand the function of the MIPS gene and phytic acid accumulation, the TaMIPS gene was characterized, and changes in gene expression and MIPS activity were analyzed. The full-length genomic DNA sequence of the TaMIPS gene, located in homologous group 4 chromosomes, was characterized. TaMIPS comprises ten exons and nine introns, with 3910 bp in total, with a cDNA open reading frame (ORF) of 1533 bp encoding a protein with 510 amino acids. The transcription of this gene was detected in roots, stems, flag leaves and immature seeds at 15 day after flowering (DAF), and high levels of gene transcripts were detected in immature seeds at 14 DAF. The enzymatic activity of MIPS was found to be high before 14 DAF, followed by a gradual reduction until seed maturity. The phytic acid concentration also gradually increased with seed maturity. A wheat cultivar with a high phytic acid content had higher enzymatic activity and higher levels of expression of MIPS than did a cultivar with low phytic acid content. The results show that the TaMIPS gene may play an important role in regulating phytate synthesis.

► We characterized a Myo-inositol-1-phosphate synthase gene (TaMIPS) in wheat. ► We analyzed gene expression and enzyme activity of two wheat cultivar seeds. ► Phytic acid accumulation in wheatgrains during seed maturation was analyzed. ► High phytate cultivar had higher enzymatic activity and gene expression. ► Wheat TaMIPS gene may be important in regulating phytate synthesis.