Discovery Of Novel Genes Involved In The Metabolism Of Phytic Acid In Maize

Phytic acid and its metabolic intermediates are involved in many physiological regulationpathways, but the metabolism pathway of phytic acid is poorly known in the plant in spite of itsirreplaceable biological functions. In this research, we employ an association population consisted of527maize inbred lines for genome wide association study (GWAS), and get some candidate genes.we gathered the seeds of those inbred lines from three different locations in two years, totally1104samples were gathered and detect the content of five type inositol phosphates in the seeds of thoseinbred lines by LC-MS. The heritability (H) of each type of inositol phosphates were calculated and thecontent of InsP2(IP2) and inorganic phosphorus (Pi) were chosen as the traits data to ran a GWAS asthey have the highest heritability, with518738SNPs as molecular markers. Approximately35SNP sitesthat have high levels of correlation with the traits variation in this population (observed value–log(p)＞5.72) were selected as candidates, and the transcript sequences of them were also obtained from theannotation file. We screen those genes through bioinformatics method to analyze the domains andpredict the functions related to the synthesis of inositol phosphates. Then we get nine genes that mostlikely have some conserved domains and functions that have relations with the target metabolicpathway;To get more evidences to support the GWAS result, we analysis the3known genes’(MIK, ITPK-1,LPA-1) expression profile in different tissues of maize especially in the embryo (where is the mainlocation of the phytic acid synthesis) through real-time fluorescence quantitative PCR (Q-RT-PCR). Theresults show that those three genes co-expressed in the embryo and coordinate with the phytic acidsynthesis processes. In addition, their expression tendency can be distinguished with each other for theyparticipate in different step of the synthesis of phytic acid. By analysis of the nine candidate genes, wefound five of them co-expressed with the three known genes. GENE3, GENE5and GENE6have thesame expression tendency with the known MIK gene. Therefore we assume that they may participate inthe earlier stage of the phytic acid synthesis. GENE2and GENE7have the same expression tendencywith the known ITPK-1gene, we presume that they may participate in the middle stage of the phyticacid synthesis.We analysis those five candidate genes form four different aspects including GWAS,bioinformatics, gene co-expression and gene-metabolic pathway coordination, the evidences from thoseaspects are coincident, and further study on those five genes may exploit a new space on the domain ofinositol phosphates metabolic research and provide breaking points to promote the development aboutthe metabolism research of phytic acid, through more directed evidences are needed to support ourwork.