Phytic acid (myo-inositol-1, 2, 3, 4, 5, 6-hexakisphosphate or Ins P 6 ) typically represents approximately 75% to 80% of maize (Zea mays) seed total P. Here we describe the origin, inheritance, and seed phenotype of two non-lethal maize low phytic acid mutants, lpa1-1 and lpa2-1. The loci map to two sites on chromosome 1S. Seed phytic acid P is reduced in these mutants by 50% to 66% but seed total P is unaltered. The decrease in phytic acid P in mature lpa1-1 seeds is accompanied by a corresponding increase in inorganic phosphate (P i ). In mature lpa2-1 seed it is accompanied by increases in P i and at least three other myo-inositol (Ins) phosphates (and/or their respective enantiomers): d-Ins(1,2,4,5,6) P 5 ; d-Ins (1,4,5,6) P 4 ; and d-Ins(1,2,6) P 3 . In both cases the sum of seed P i and Ins phosphates (including phytic acid) is constant and similar to that observed in normal seeds. In both mutants P chemistry appears to be perturbed throughout seed development. Homozygosity for either mutant results in a seed dry weight loss, ranging from 4% to 23%. These results indicate that phytic acid metabolism during seed development is not solely responsible for P homeostasis and indicate that the phytic acid concentration typical of a normal maize seed is not essential to seed function.

Phosphorous in soybean [Glycine max (L.) Merr.] seed is stored primarily as phytic acid, which is nutritionally unavailable to nonruminant livestock. The objective of this study was to isolate mutations that reduce soybean seed phytic acid P and increase seed inorganic P. Following treatment with ethyl methanesulfonate, M2 through M6 plants were screened for high seed inorganic P. Seeds of M2 plants high in inorganic P produced progenies high in inorganic P through the M6 generation. M6 progenies of one plant averaged 6.84 g kg−1 seed phytic acid and inorganic P varied from 2.34 to 4.41 g kg−1 or 60 to 66% of phytic acid P plus inorganic P. M6 progenies of a second plant averaged 10.89 g kg−1 phytic acid and varied from 1.21 to 3.84 g kg−1 inorganic P, representing from 47 to 51% of the sum of phytic acid P plus inorganic P. In contrast, nonmutant seeds of the check cultivar Athow contained 15.33 g kg−1 phytic acid and averaged 0.74 g kg−1 inorganic P, representing 15% of the sum of phytic acid P plus inorganic P. Low phytic acid and high inorganic P in these progenies should increase the nutritional value of soy meal and reduce excess P in livestock manure.

Raboy, 1997). Trace levels (Ͻ5% of total Ins P) of "lower" Ins polyphosphates (Ins bis-, tris-, tetrakis-, and Phytic acid (myo-inositol 1,2,3,4,5,6 hexakisphosphate) is the most pentakisphosphates) are also often observed in mature, abundant form of phosphorus (P) in seeds and is virtually indigestible by humans or non-ruminant livestock. It was hypothesized that one wild-type seeds. Normally, inorganic P (P i ) typically repclass of maize (Zea mays L.) and barley (Hordeum vulgare L.) low resents about 5% (Ϯ3%) of seed total P and all other phytic acid mutations, designated lpa1, interrupt myo-inositol supply forms of organic P (DNA, RNA, free nucleotides, phosduring seed development and may be mutations of the myo-inositol pholipids, sugar phosphates, etc.), referred to here as 1-phosphate synthase (MIPS) gene. This study describes the isolation, cellular P, represent about 10 to 20% of seed total P. inheritance, and genetic mapping of the first rice lpa1 mutation and Substantial variation in seed total P of a given line or reexamines the MIPS/lpa1 candidate gene hypothesis in rice. Grain genotype can result from environmental or genotypic from 3632 rice M2 lines, derived from gamma-irradiated seed, was factors that alter the supply of P to the developing seed. screened for the lpa phenotype. Two mutations, one lethal and oneIn wild-type plants, this variation is mostly due to varianon-lethal, were identified. The non-lethal mutation is phenotypically tion in seed phytic acid P, while the P i and cellular P similar to maize and barley lpa1 mutants and was designated rice lpa1-1. Homozygosity for rice lpa1-1 reduces the phytic acid portion fractions of seed total P tend to remain constant (reof seed P from 71 to 39% and increases the inorganic portion of seed viewed in Raboy, 1997). P from 5 to 32%, with little effect on total seed P. This rice lpa1Chemically induced, non-lethal recessive mutants that mutation was mapped to a 2.2-cM interval on chromosome 2L. A decrease seed phytic acid content have been isolated single-copy rice MIPS gene was mapped to a locus on rice chromosome and genetically mapped in maize (Zea mays L.; Raboy 3 that is orthologous to MIPS loci on maize chromosome 1S (near and Gerbasi, 1996; Raboy et al., 2000) and barley maize lpa1 ) and barley chromosome 4H. Unlike maize lpa1, the rice (Hordeum vulgare L.; Larson et al., 1998; Rasmussen and barley lpa1 mutations loci are clearly distinguishable from this and Hatzak, 1998). These low phytic acid (lpa) mutacanonical MIPS gene. No relationship can be inferred between the tions have the potential to alleviate the environmental maize, barley, and rice lpa1 loci. Although this canonical MIPS gene and nutritional problems associated with phytic acid in may be an appropriate target for controlling seed phytic acid synthesis, modifications of other genes (e.g., maize lpa2, barley lpa1, barley

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Much of the P in corn (Zea mays L.) grain is present in the form of phytic acid. Phytic acid P is unavailable to monogastric animals with most being excreted in the waste. As a result, the substantial P stores in grain are essentially wasted and may contribute to water pollution rather than animal productivity. The initial goal of this research was to isolate chemically induced mutants with reduced levels of phytic acid P in corn. Such mutants, referred to as low phytic acid or Ipa, were isolated and were found to have little or no other effect on kernel composition including no effect on total grain P content. The first mutant characterized, Ipal‐1, a 65% reduction in phytic acid and is accompanied by a molar‐equivalent increase in inorganic P. This mutant was backcrossed into elite corn inbred lines and resulting hybrids were evaluated for yield and other important agronomic traits. Preliminary field trials indicated germination, stalk strength, grain moisture at harvest, and flowering date were not affected by Ipal‐1. Some, but not all, Ipal‐1 hybrids had yield reductions. In a preliminary chick feeding trial, the low phytic acid grain resulted in greater P availability and reduced P content in the waste. Altering the phytic acid content genetically in corn is possible and may have the potential to improve feeding efficiencies and reduce P released to the environment.

Background: Genetically modified, low-phytic acid strains of maize were developed to enhance mineral absorption, but have not been tested previously in humans. Objectives: We evaluated the mineral and phytic acid contents of a low-phytic acid "flint" maize (LPM, the lpa-1-1 mutant) and its parent, wild-type strain (WTM) and measured iron absorption from tortillas prepared with each type of maize and from a reference dose of ferrous ascorbate. Design: Proximate composition and mineral and phytic acid contents were measured by standard techniques. Iron absorption from tortillas was evaluated by using the extrinsic tag method and was measured as the incorporation of radiolabeled iron into the red blood cells of 14 nonanemic men 2 wk after intake. Results: The phytic acid content of LPM was 3.48 mg/g, Ϸ35% of the phytic acid content of WTM; concentrations of macronutrients and most minerals were not significantly different between strains. Iron absorption results were adjusted to 40% absorption of ferrous ascorbate. Iron absorption was 49% greater from LPM (8.2% of intake) than from WTM (5.5% of intake) tortillas (P < 0.001, repeated-measures analysis of variance). Conclusion: Consumption of genetically modified, low-phytic acid strains of maize may improve iron absorption in human populations that consume maize-based diets.Am J Clin Nutr 1998;68:1123-7. KEY WORDSIron, iron absorption, iron deficiency, phytic acid, corn, maize, tortilla, men INTRODUCTIONNonheme iron from cereals and other plant sources is poorly absorbed because of the presence of inhibitors of iron absorption, such as phytic acid, tannins, and selected dietary fibers, which irreversibly bind iron in the intestinal lumen (1-3). One possible approach to improving iron absorption is to reduce the phytic acid content of foods by genetically modifying their capacity to synthesize phytic acid (4; V Raboy et al, unpublished observations, 1994). Recent experiments indicate that much of the phytic acid in maize and other cereals can be removed through genetic engineering without affecting the total phosphorus content of the grain or the health of the plant (V Raboy, K Young, P Gerbasi, unpublished observations, 1994). This offers great promise for human trace mineral nutrition, especially in populations that are primarily dependent on plantderived diets.Before promoting the large-scale production of low-phytic acid grain for human consumption, it is necessary that we determine whether a reduction in phytic acid content affects other components of the grain and whether low-phytic acid mutants do indeed have the expected effect on mineral absorption from mixed diets consumed by humans. We therefore conducted several laboratory analyses of the nutrient content of low-phytic acid and unmodified strains of maize and completed a clinical study of the effect of substituting the low-phytic acid maize on the absorption of nonheme iron from maize tortillas. The studies were conducted with maize tortillas because this is the most common form in which maize is ...