Abstract:

It is well known that the phytic acid (myo-inositol-1, 2, 3, 4, 5, 6-hexakisphosphate or Ins P6) in maize (Zea mays), wheat (Triticum compactum), rice (Oryza sativa), and soybean (Glycine max) is an anti-nutritional factor in grains, phytic acid typically
represents approximately 80% of maize seed total phosphorus. The identification of mutants with low phytic acid (lpa) is a possible solution to solve the problem. In this study, the content of inorganic phosphorus of twenty maize inbred lines were analyzed by colorimetric reagent, the inorganic phosphorus content of Qi 319 was about 0.93 mg mg^-1, which was higher than that of control material
(0.15 mg mg^-1), further investigation of phytic acid based on standard curve indicated that the content of phytic acid in Qi 319 grains was 1.31 mg mg^-1, close to the maize lpa241/lpa241 mutant (1.20 mg mg^-1) identified by Nielsen’s laboratory in 2003, which was
significantly lower than that of Lpa241/Lpa241 wild type and control maize inbred lines (>2.8 mg mg^-1). F₁ seeds derived from Qi
319 and wild type Lpa241/Lpa241 crossing showed low inorganic phosphorus, indicated that the gene controlling low phytic acid of
Qi 319 was recessive, homozygous low phytic acid seed was identified from Qi 319 ×/Lpa241/lpa241 F₁ seeds suggested that lpa loci of Qi 319 may allelic to lpa241/lpa241. To investigate the mechanism of lpa in Qi 319, the content of myo-inositol-3-phophate
synthase (MIPS) was assayed Western blot by using anti-MIPS antibody derived from Arabidopsis MIPS protein, according to se
quence analysis, the similarity of amino acid between maize and Arabidopsis MIPS protein is 88%. In contrast with the low content of
MIPS in lpa241/lpa241, the expression of MIPS in Qi 319 increased significantly, suggesting that both mutants are related to MIPS,
but their mechanism is different from each other. It is worthwhile to point out that the agronomic behavior of reported lpa mutant is not satisfying for breeding applications, while Qi 319 is a wildly used inbred line with several combinations in production. This discovery will broaden its application and provide a novel resource for lpa breeding program.

Key words:

Maize, Inbred line, Low phytic acid, MIPS