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

Phytic acid is regarded as the most anti-nutrients in wheat (Triticumaestivum L.) grain because it can strongly bind to essential mineral cation, affectingbiological effectiveness of iron, zinc and other mineral elements in food or feed. TheD-myo-inositol-3-phosphate synthase (MIPS) is the key enzyme in the first step ofphytic acid synthesis pathway which catalysis glucose-6-phosphate toinositol-3-phosphate. More studies have been focused on MIPS genes and itsrelationship with phytic acid accumulation in corn and rice. Wheat is the primarystaple food for almost one-third of the world’s population. However, limitedmolecular information exists about the MIPS gene in wheat seeds, especially aboutthe relationship between transcriptional and enzymatic activity of MIPS and phytatesynthesis during seed development. So the TaMIPS genes were characterized, geneexpression pattern during grain filling and the relationship with the grain phytic acidaccumulation was analyzed. The results are as follow:Using homology cloning and insilico cloning methods, we achieved the wheatMIPS cDNA sequence and its genomic DNA sequence. The length of cDNA sequenceis1724bp, with a cDNA open reading frame (ORF) of1533bp, including52bp inthe5’ untranslated region and139bp in the3’ untranslated region. The MIPS geneencodes a protein with510amino acids. The MIPS genomic DNA sequences locatedin homologous group4A chromosomes and4D chromosomes were cloned fromwheat, and these sequences were named TaMIPS-4A and TaMIPS-4D, repectively. Aset of Chinese Spring nullisomic-tetrasomic were used to determine the chromosomallocation of TaMIPS. The full-length TaMIPS-4A contains3910bp, and theTaMIPS-4D sequence is3863bp, but they all comprises ten exons and nine introns.Fertilizer application can influence grain phytic acid, iron and zinc elementscontent. This study showed that increasing the nitrogen fertilizer application rate canenhance MIPS gene expression and improve MIPS enzyme activity; With increasingnitrogen fertilizer, grain inorganic phosphorus content was reduced, while a small increase was showed in phytic acid content. The increase in iron and zinc content wasgreater than phytic acid content. Thus, PA/Zn molar ratio and PA/Fe mole ratio weredropped with nitrogen fertilizer application rate increasing. MIPS gene expression andthe MIPS enzyme activity was decreased with zinc fertilizer application rateincreasing. At the same time, inorganic phosphorus content, zinc and iron contentwere increased, while phytic acid content was decreased. Thus PA/Zn molar ratio andPA/Fe molar ratio were decreased and bioavailability of mineral elements wasimproved. The results shows that both iron and zinc element bioavailability can beimproved by zinc fertilizer application. Nitrogen fertilizer had greater effect on ironelement bioavailability than on zinc element. It suggests that appropriate nitrogen andzinc fertilizer application can decrease phytic acid content, and improve iron and zincelement bioavailability.