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Hambidge KM, Huffer JW, Raboy V, Grunwald GK, Westcott JL, Sian L, Miller LV, Dorsch JA, Krebs NF. Zinc absorption from low-phytate hybrids of maize and their wild-type isohybrids. Am J Clin Nutr 2004; 79:1053-9. [PMID: 15159236 DOI: 10.1093/ajcn/79.6.1053] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Identification of allelic variants in a single gene that determine the phytate content of maize kernels and the subsequent breeding of low-phytate maize have facilitated studies designed to determine quantitatively the effects of maize phytate on the bioavailability of minerals in maize. OBJECTIVE The objective was to determine the relation between the fractional absorption of zinc (FAZ) and the phytate content and phytate:zinc molar ratios of maize tortillas prepared from hybrids with different phytate contents. DESIGN Six healthy adults were fed, as the only food for 2 d, maize tortillas prepared from 1 of 2 low-phytate mutants: lpa1-1 (lpa1-1-LP) or Nutridense Low Phytate (ND-LP), which have phytate reductions of approximately 60% and approximately 80%, respectively, compared with their respective wild-type isohybrids. Four additional subjects were fed tortillas prepared from the corresponding wild-type isohybrids (lpa1-1-WT and ND-WT) according to the same study design. Meals were extrinsically labeled with zinc stable isotopes, and FAZ was determined with a dual-isotope-tracer ratio technique. Overall FAZ values were examined in relation to dietary phytate and phytate:zinc molar ratios by using a mixed nonlinear regression model. RESULTS The mean (+/-SD) FAZ values from tortillas prepared from ND-LP, lpa1-1-LP, lpa1-1-WT, and ND-WT were 0.38 +/- 0.07, 0.28 +/- 0.04, 0.15 +/- 0.07, and 0.13 +/- 0.05, respectively. A negative relation (P < 0.001) was found between FAZ and both dietary phytate and the phytate:zinc molar ratio. The effect of dietary zinc (8-14 mg Zn/d) under these experimental conditions was not significant. CONCLUSIONS FAZ from maize tortillas is positively related to the extent of phytate reduction achieved with low-phytate hybrids.
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Affiliation(s)
- K Michael Hambidge
- University of Colorado Health Sciences Center, Department of Pediatrics, Section of Nutrition, Denver 80262, USA.
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202
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Jang DA, Fadel JG, Klasing KC, Mireles AJ, Ernst RA, Young KA, Cook A, Raboy V. Evaluation of low-phytate corn and barley on broiler chick performance. Poult Sci 2003; 82:1914-24. [PMID: 14717549 DOI: 10.1093/ps/82.12.1914] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Grains produced by low-phytate barley and corn isolines homozygous for each species' respective low phytic acid 1-1 allele were compared to grain produced by near-isogenic normal or wild-type barley and corn in broiler chick feeds. Cobb x Cobb (384) chicks were used in a 10-d study. A randomized complete block design with a factorial arrangement of 2 x 2 x 3 was used with 4 replicates (8 chicks / replicate) per treatment. Twelve isocaloric and isonitrogenous treatment diets were formulated to contain 2 types of grain (barley and corn), 2 levels of grain (40% and 60%), and 3 sources of available P (wild-type grain, wild-type P-supplemented grain, and low-phytate grain). Growth parameters, bone parameters, total bone mineral, and apparent digestibilities were measured. The mean growth and bone responses were 1) higher for barley diets compared to corn diets, 2) higher for 60% grain inclusion compared to 40%, 3) higher for low-phytate compared to wild-type grains, and 4) not different for low-phytate compared to P-supplemented wild-type grain diets. Chicks fed low-phytate-based diets excreted 33 and 43% less P than chicks fed wild-type and P-supplemented wild-type diets, respectively. Correlations between percentage bone ash, total bone ash, and bone strength indicated a strong relationship and appear to support the use of bone strength analysis as a simpler method than ash content determination as an indication of P status. Feeding low-phytate grains will reduce the need for supplemental P in chick diets.
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Affiliation(s)
- D A Jang
- Department of Animal Science, University of California, Davis, California 95616-8521, USA
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203
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Abstract
myo-Inositol-1,2,3,4,5,6-hexakisphosphate (Ins P(6)) was first described as an abundant form of phosphorus in plant seeds and other plant tissues and dubbed "phytic acid". Subsequently it was found to be a common constituent in eukaryotic cells, its metabolism a basic component of cellular housekeeping. In addition to phosphate, myo-inositol (Ins) and mineral storage and retrieval in plant organs and tissues, other roles for Ins P(6) include service as a major metabolic pool in Ins phosphate and pyrophosphate pathways involved in signaling and regulation; possibly as an effector or ligand in these processes; as a form of energy currency and in ATP regeneration; in RNA export and DNA repair; and as an anti-oxidant. The relatively recent demonstration that pyrophosphate-containing derivatives of Ins P(6) can function as phosphate donors in the regeneration of ATP is reminiscent of the proposal, made four decades ago in studies of seed development, that Ins P(6) itself may serve in this function. Studies of Ins P(6) in non-plant systems rarely include the consideration that this compound might represent a significant fraction of cellular P; cellular phosphate nutrition has been viewed as either not interesting or of little importance. However, there may be few fundamental differences among diverse eukaryotes in both the metabolic pathways involving Ins P(6) and the spectrum of possible roles for it and its metabolites.
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Affiliation(s)
- Victor Raboy
- USDA-ARS, 1691 South 2700 West, Aberdeen, ID 83210, USA.
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204
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Yip W, Wang L, Cheng C, Wu W, Lung S, Lim BL. The introduction of a phytase gene from Bacillus subtilis improved the growth performance of transgenic tobacco. Biochem Biophys Res Commun 2003; 310:1148-54. [PMID: 14559235 DOI: 10.1016/j.bbrc.2003.09.136] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Phytate, the main form of phosphorus storage in plant seeds, is well known to be an anti-nutrient and a major source of phosphorus pollution in animal manure. To improve phosphorus bio-availability, we introduced a recently characterized phytase from Bacillus subtilis into the cytoplasm of tobacco cells. Although the introduction of acid fungal phytase from Aspergillus niger in previous studies did not result in any phenotypic changes in tobacco, here we show that a tobacco line transformed with a neutral phytase exhibited phenotypic changes in flowering, seed development, and response to phosphate deficiency. The transgenic line showed an increase in flower and fruit numbers, small seed syndrome, lower seed IP6/IP5 ratio, and enhanced growth under phosphate-starvation conditions compared with the wildtype. The results suggest that the over-expression of Bacillus phytase in the cytoplasm of tobacco cells shifts the equilibrium of the inositol phosphate biosynthesis pathway, thereby making more phosphate available for primary metabolism. The approach presented here can be applied as a strategy for boosting productivity in agriculture and horticulture.
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Affiliation(s)
- Wingkin Yip
- Department of Botany, The University of Hong Kong, Pokfulam, Hong Kong, China.
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205
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Pilu R, Panzeri D, Gavazzi G, Rasmussen SK, Consonni G, Nielsen E. Phenotypic, genetic and molecular characterization of a maize low phytic acid mutant (lpa241). TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2003; 107:980-7. [PMID: 14523526 DOI: 10.1007/s00122-003-1316-y] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2002] [Accepted: 03/26/2003] [Indexed: 05/10/2023]
Abstract
Phytic acid, myo-inositol 1,2,3,4,5,6-hexakisphosphate, is the major storage compound of phosphorous (P) in plants, predominantly accumulating in seeds (up to 4-5% of dry weight) and pollen. In cereals, phytic acid is deposited in embryo and aleurone grain tissues as a mixed "phytate" salt of potassium and magnesium, although phytates contain other mineral cations such as iron and zinc. During germination, phytates are broken down by the action of phytases, releasing their P, minerals and myo-inositol which become available to the growing seedling. Phytic acid represents an anti-nutritional factor for animals, and isolation of maize low phytic acid ( lpa) mutants provides a novel approach to study its biochemical pathway and to tackle the nutritional problems associated with it. Following chemical mutagenesis of pollen, we have isolated a viable recessive mutant named lpa 241 showing about 90% reduction of phytic acid and about a tenfold increase in seed-free phosphate content. Although germination rate was decreased by about 30% compared to wild-type, developement of mutant plants was apparentely unaffected. The results of the genetic, biochemical and molecular characterization experiments carried out by SSR mapping, MDD-HPLC and RT-PCR are consistent with a mutation affecting the MIPS1S gene, coding for the first enzyme of the phytic acid biosynthetic pathway.
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Affiliation(s)
- R Pilu
- Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy
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206
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Bentsink L, Yuan K, Koornneef M, Vreugdenhil D. The genetics of phytate and phosphate accumulation in seeds and leaves of Arabidopsis thaliana, using natural variation. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2003; 106:1234-1243. [PMID: 12748774 DOI: 10.1007/s00122-002-1177-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2002] [Accepted: 10/21/2002] [Indexed: 05/24/2023]
Abstract
Phytate (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6) is the most abundant P-containing compound in plants, and an important anti-nutritional factor, due to its ability to complex essential micro-nutrients, e.g. iron and zinc. Analysis of natural variation for InsP6 and Pi accumulation in seeds and leaves for a large number of accessions of Arabidopsis thaliana, using a novel method for InsP6 detection, revealed a wide range of variation in InsP6 and Pi levels, varying from 7.0 mg to 23.1 mg of InsP6 per gram of seed. Quantitative trait locus (QTL) analysis of InsP6 and Pi levels in seeds and leaves, using an existing recombinant inbred line population, was performed in order to identify a gene(s) that is (are) involved in the regulation of InsP6 accumulation. Five genomic regions affecting the quantity of the InsP6 and Pi in seeds and leaves were identified. One of them, located on top of chromosome 3, affects all four traits. This QTL appears as the major locus responsible for the observed variation in InsP6 and Pi contents in the L er/Cvi RIL population; the L er allele decreases the content of both InsP6 and Pi in seeds and in leaves. The InsP6/Pi locus was further fine-mapped to a 99-kb region, containing 13 open reading frames. The maternal inheritance of the QTL and the positive correlation between InsP6 and total Pi levels both in seeds and in leaves indicate that the difference in InsP6 level between L er and Cvi is likely to be caused by a difference in transport rather than by an alteration in the biosynthesis. Therefore, we consider the vacuolar membrane ATPase subunit G, located in the region of interest, as the most likely candidate gene for InsP6/Pi.
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Affiliation(s)
- L Bentsink
- Laboratory of Genetics, Wageningen University, Arboretumaan 4, The Netherlands
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207
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Abstract
Deficiencies of iron and zinc are common worldwide. Various strategies have been used to combat these deficiencies including supplementation, food fortification and modification of food preparation and processing methods. A new possible strategy is to use biotechnology to improve trace element nutrition. Genetic engineering can be used in several ways; the most obvious is to increase the trace element content of staple foods such as cereals and legumes. This may be achieved by introduction of genes that code for trace element-binding proteins, overexpression of storage proteins already present and/or increased expression of proteins that are responsible for trace element uptake into plants. However, even very high levels of expression may not substantially increase the iron and zinc contents unless many atoms of trace elements are bound per protein molecule. Another possibility is to introduce a protein that specifically enhances trace element absorption even in the presence of naturally occurring inhibitors, thus improving bioavailability. Genetically modifying plants so that their contents of inhibitors of trace element absorption such as phytate are substantially reduced is another approach. Increasing the expression of compounds that enhance trace element absorption such as ascorbic acid is also a possibility, although this has received limited attention so far. Iron absorption may be increased by higher ascorbic or citric acid content but require overexpression of enzymes that are involved in the synthetic pathways. Finally, a combination of all of these approaches perhaps complemented with conventional breeding techniques may prove successful.
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Affiliation(s)
- Bo Lönnerdal
- Department of Nutrition, University of California, Davis, CA 95616, USA.
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208
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Ceylan N, Scheideler SE, Stilborn HL. High available phosphorus corn and phytase in layer diets. Poult Sci 2003; 82:789-95. [PMID: 12762402 DOI: 10.1093/ps/82.5.789] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
High available phosphorus corn (HAP) developed using the low phytic acid 1-1 (lpal-1) allele of the corn LPA1 gene containing 0.27% P, with 0.17% nonphytate P (NPP), was compared to near isogenic normal corn (LPA1), which contained 0.23% P and 0.05% NPP. Five levels of NPP from either HAPC or normal corn (0.40, 0.35, 0.30, 0.25 and 0.20% + 300 phytase units (FTU)/kg microbial phytase) were combined in a 2 x 5 factorial experiment for a total of 10 dietary treatments. Each dietary treatment was fed to eight replicate cages with five Hy-Line W-36 hens per replicate cage from 20 to 40 wk of age. Feed consumption and egg production were not significantly affected by dietary NPP level or corn type. Feed conversion ratio (g feed:g egg mass) was improved at the 0.35% NPP level (1.856) compared to the other levels of NPP--0.40, 0.30, 0.25, and 0.20% + phytase having feed conversion ratios of 1.872, 1.905, 1.930, and 1.898, respectively. Egg weight and egg mass decreased significantly as dietary NPP decreased; diets with 0.20% NPP plus phytase had equal egg mass to the 0.35 and 0.40% NPP diets. A significant corn type x NPP interaction effect was observed for egg weight, such that within the HAP corn diets, egg weight decreased more markedly at the 0.25% NPP levels compared to the normal corn 0.25% NPP diets. Specific gravity was not affected by dietary treatment, but percent dry shell was improved at the lower AP levels and with phytase treatment. Dietary NPP level and corn type had no significant effect on bone ash. Excreta levels of total phosphorus decreased significantly as dietary NPP decreased and were lower in the HAP corn excreta compared to normal corn excreta. Total P, Ca, Zn, Cu, and Mn retention were significantly affected by NPP level and corn type. HAP corn reduced Ca, Zn, Cu, and Mn retention compared to normal corn; this negative effect was alleviated by phytase supplementation to HAP corn diets. HAP corn allowed less dicalcium phosphate supplementation in layer diets compared to normal corn while supporting equal egg production. Phytase supplementation of low NPP diets had no significant positive effects on egg production parameters in either corn type diets.
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Affiliation(s)
- N Ceylan
- Department of Animal Sciences, University of Nebraska, Lincoln, Nebraska 68583-0908, USA
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209
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Abstract
Three selected aspects of human zinc homeostasis and requirements are reviewed with special reference to studies undertaken by the author and his colleagues: 1) the implications for the calculation of physiologic requirements for zinc of the interrelationship between two key variables of zinc homeostasis, intestinal excretion of endogenous zinc and total absorbed zinc, are examined at levels of absorption below those necessary to meet physiologic requirements; 2) a method for deriving average dietary zinc requirements from zinc-stable isotope tracer/metabolic studies is illustrated with examples of studies being conducted in developing countries; and 3) the effect of reduction of high intakes of phytic acid on zinc bioavailability is examined with test meals prepared from low-phytic-acid maize or isohybrid wild-type control maize.
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Affiliation(s)
- Michael Hambidge
- Department of Pediatrics, Section of Nutrition, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
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210
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Dorsch JA, Cook A, Young KA, Anderson JM, Bauman AT, Volkmann CJ, Murthy PPN, Raboy V. Seed phosphorus and inositol phosphate phenotype of barley low phytic acid genotypes. PHYTOCHEMISTRY 2003; 62:691-706. [PMID: 12620321 DOI: 10.1016/s0031-9422(02)00610-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
myo-Inositol-1,2,3,4,5,6-hexakisphosphate (Ins P(6) or "phytic acid") typically represents approximately 75% of the total phosphorus and >80% of soluble myo-inositol (Ins) phosphates in seeds. The seed phosphorus and Ins phosphate phenotypes of four non-lethal barley (Hordeum vulgare L.) low phytic acid mutations are described. In seeds homozygous for M 635 and M 955 reductions in Ins P(6), approximately 75 and >90% respectively, are accompanied by reductions in other Ins phosphates and molar-equivalent increases in Pi. This phenotype suggests a block in supply of substrate Ins. In seeds homozygous for barley low phytic acid 1-1 (lpa1-1), a 45% decrease in Ins P(6) is mostly matched by an increase in Pi but also accompanied by small increases in Ins(1,2,3,4,6)P(5). In seeds homozygous for barley lpa2-1, reductions in seed Ins P(6) are accompanied by increases in both Pi and in several Ins phosphates, a phenotype that suggests a lesion in Ins phosphate metabolism, rather than Ins supply. The increased Ins phosphates in barley lpa2-1 seed are: Ins(1,2,3,4,6)P(5); Ins(1,2,4,6)P(4) and/or its enantiomer Ins(2,3,4,6)P(4); Ins(1,2,3,4)P(4) and/or its enantiomer Ins(1,2,3,6)P(4); Ins(1,2,6)P(3) and/or its enantiomer Ins(2,3,4)P(3); Ins(1,5,6)P(3) and/or its enantiomer Ins(3,4,5)P(3) (the methods used here cannot distinguish between enantiomers). This primarily "5-OH" series of Ins phosphates differs from the "1-/3-OH" series observed at elevated levels in seed of the maize lpa2 genotype, but previous chromosomal mapping data indicated that the maize and barley lpa2 loci might be orthologs of a single ancestral gene. Therefore one hypothesis that might explain the differing lpa2 phenotypes is that their common ancestral gene encodes a multi-functional, Ins phosphate kinase with both "1-/-3-" and "5-kinase" activities. A putative pyrophosphate-containing Ins phosphate, possibly an Ins P(7), was also observed in the mature seed of all barley genotypes except lpa2-1. Barley M 955 indicates that at least for this species, the ability to accumulate Ins P(6) can be nearly abolished while retaining at least short-term ( approximately 1.0 years) viability.
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Affiliation(s)
- John A Dorsch
- USDA-ARS, 1691 South 2700 West, Aberdeen, ID 83210, USA
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211
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Affiliation(s)
- Brian Q Phillippy
- United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA 70124, USA
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212
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Shi J, Wang H, Wu Y, Hazebroek J, Meeley RB, Ertl DS. The maize low-phytic acid mutant lpa2 is caused by mutation in an inositol phosphate kinase gene. PLANT PHYSIOLOGY 2003; 131:507-15. [PMID: 12586875 PMCID: PMC166827 DOI: 10.1104/pp.014258] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2002] [Revised: 10/11/2002] [Accepted: 11/06/2002] [Indexed: 05/18/2023]
Abstract
Reduced phytic acid content in seeds is a desired goal for genetic improvement in several crops. Low-phytic acid mutants have been used in genetic breeding, but it is not known what genes are responsible for the low-phytic acid phenotype. Using a reverse genetics approach, we found that the maize (Zea mays) low-phytic acid lpa2 mutant is caused by mutation in an inositol phosphate kinase gene. The maize inositol phosphate kinase (ZmIpk) gene was identified through sequence comparison with human and Arabidopsis Ins(1,3,4)P(3) 5/6-kinase genes. The purified recombinant ZmIpk protein has kinase activity on several inositol polyphosphates, including Ins(1,3,4)P(3), Ins(3,5,6)P(3), Ins(3,4,5,6)P(4), and Ins(1,2,5,6)P(4). The ZmIpk mRNA is expressed in the embryo, the organ where phytic acid accumulates in maize seeds. The ZmIpk Mutator insertion mutants were identified from a Mutator F(2) family. In the ZmIpk Mu insertion mutants, seed phytic acid content is reduced approximately 30%, and inorganic phosphate is increased about 3-fold. The mutants also accumulate myo-inositol and inositol phosphates as in the lpa2 mutant. Allelic tests showed that the ZmIpk Mu insertion mutants are allelic to the lpa2. Southern-blot analysis, cloning, and sequencing of the ZmIpk gene from lpa2 revealed that the lpa2-1 allele is caused by the genomic sequence rearrangement in the ZmIpk locus and the lpa2-2 allele has a nucleotide mutation that generated a stop codon in the N-terminal region of the ZmIpk open reading frame. These results provide evidence that ZmIpk is one of the kinases responsible for phytic acid biosynthesis in developing maize seeds.
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Affiliation(s)
- Jinrui Shi
- Pioneer Hi-Bred International, P.O. Box 1004, Johnston, Iowa 50131, USA.
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213
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Konietzny U, Greiner R. Molecular and catalytic properties of phytate-degrading enzymes (phytases). Int J Food Sci Technol 2002. [DOI: 10.1046/j.1365-2621.2002.00617.x] [Citation(s) in RCA: 229] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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214
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Veum TL, Ledoux DR, Bollinger DW, Raboy V, Cook A. Low-phytic acid barley improves calcium and phosphorus utilization and growth performance in growing pigs1. J Anim Sci 2002. [DOI: 10.1093/ansci/80.10.2663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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215
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216
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Adams CL, Hambidge M, Raboy V, Dorsch JA, Sian L, Westcott JL, Krebs NF. Zinc absorption from a low-phytic acid maize. Am J Clin Nutr 2002; 76:556-9. [PMID: 12197999 DOI: 10.1093/ajcn/76.3.556] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Phytic acid reduction in cereal grains has been accomplished with plant genetic techniques. These low-phytic acid grains provide a strategy for improving the mineral (eg, zinc) status in populations that are dependent on grains, including maize (Zea mays L.), as major dietary staples. OBJECTIVE The objective was to compare the fractional absorption of zinc from polenta prepared from maize low in phytic acid with that prepared from a wild-type isohybrid maize (control) after short-term consumption by adults whose habitual diet is low in phytic acid. DESIGN Healthy adults served as their own control subjects in a crossover design. All meals on 1 d consisted of polenta prepared from a low-phytic acid maize homozygous for the recessive low phytic acid 1-1 (lpa1-1). On the preceding or following day, all meals consisted of polenta prepared from a sibling isohybrid homozygous wild-type maize with a "normal" phytic acid content. The low-phytic acid maize contained approximately 60% less phytic acid than did the wild-type maize. All test meals were extrinsically labeled with zinc stable-isotope tracers. The fractional absorption of zinc was determined on the basis of fecal enrichment. RESULTS The molar ratios of phytic acid to zinc in the polenta prepared from lpa1-1 maize and the wild-type maize were 17:1 and 36:1, respectively. The corresponding fractional absorptions of zinc were 0.30 +/- 0.13 and 0.17 +/- 0.11, respectively (P < 0.005). CONCLUSION Substitution of a low-phytic acid grain in a maize-based diet is associated with a substantial increase in zinc absorption.
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Affiliation(s)
- Christina L Adams
- Section of Nutrition, Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80220, USA
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217
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Otegui MS, Capp R, Staehelin LA. Developing seeds of Arabidopsis store different minerals in two types of vacuoles and in the endoplasmic reticulum. THE PLANT CELL 2002; 14:1311-27. [PMID: 12084829 PMCID: PMC150782 DOI: 10.1105/tpc.010486] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2001] [Accepted: 03/01/2002] [Indexed: 05/18/2023]
Abstract
Mineral-accumulating compartments in developing seeds of Arabidopsis were studied using high-pressure-frozen/freeze-substituted samples. Developing seeds store minerals in three locations: in the protein storage vacuoles of the embryo, and transiently in the endoplasmic reticulum (ER) and vacuolar compartments of the chalazal endosperm. Energy dispersive x-ray spectroscopy and enzyme treatments suggest that the minerals are stored as phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate) salts in all three compartments, although they differ in cation composition. Whereas embryo globoids contain Mg, K, and Ca as cations, the chalazal ER deposits show high levels of Mn, and the chalazal vacuolar deposits show high levels of Zn. The appearance of the first Zn-phytate crystals coincides with the formation of network-like extensions of the chalazal vacuoles. The core of these networks consists of a branched network of tubular ER membranes, which are separated from the delineating tonoplast membranes by a layer of cytosolic material. Degradation of the networks starts with the loss of the cytosol and is followed by the retraction of the ER, generating a network of collapsed tonoplast membranes that are resorbed. Studies of fertilized fis2 seeds, which hyperaccumulate Zn-phytate crystals in the chalazal vacuolar compartments, suggest that only the intact network is active in mineral sequestration. Mineral determination analysis and structural observations showed that Zn and Mn are mobilized from the endosperm to the embryo at different developmental stages. Thus, Zn appears to be removed from the endosperm at the late globular stage, and Mn stores appear to be removed at the late bent-cotyledon stage of embryo development. The disappearance of the Mn-phytate from the endosperm coincides with the accumulation of two major Mn binding proteins in the embryo, the 33-kD protein from the oxygen-evolving complex of photosystem II and the Mn superoxide dismutase. The possible functions of transient heavy metal storage in the chalazal endosperm are discussed. A model showing how phytic acid, a potentially cytotoxic molecule, is transported from its site of synthesis, the ER, to the different mineral storage sites is presented.
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Affiliation(s)
- Marisa S Otegui
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA.
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218
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Yoshida KT, Fujiwara T, Naito S. The synergistic effects of sugar and abscisic acid on myo-inositol-1-phosphate synthase expression. PHYSIOLOGIA PLANTARUM 2002; 114:581-587. [PMID: 11975732 DOI: 10.1034/j.1399-3054.2002.1140411.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
1L-myo-inositol-1-phosphate [Ins(1)P1] synthase (EC 5.5.1.4) catalyses the formation of Ins(1)P1 from glucose-6-phosphate, the first step in the biosynthesis of myo-inositol. Ins(1)P1 is a precursor of phytin (inositol hexakisphosphate), a storage form of phosphate and cations in seeds. Since sucrose and abscisic acid (ABA) are known to affect synthesis of storage compounds in seeds, we investigated the effects of ABA and sucrose on Ins(1)P1 synthase gene (RINO1) expression in cultured cells derived from the scutellum of mature rice seeds. Higher levels of RINO1 transcript accumulation were evident after treatment with either sucrose (10-100 mM) or ABA (10-8 M to 10-4 M). Glucose was also effective in the upregulation, whereas mannitol was not, suggesting that sucrose and glucose acted as metabolizable sugars and not as osmotica. Treatment with ABA and sucrose together resulted in much higher levels of transcript accumulation, suggesting a synergistic induction of the Ins(1)P1 synthase gene.
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Affiliation(s)
- Kaoru T Yoshida
- aGraduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan bGraduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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219
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Abstract
Populations that depend on grains and legumes as staple foods consume diets rich in phytic acid (myo-inositol-1,2,3,4,5,6-hexkisphosphate), the storage form of phosphorus in seeds. This compound binds tightly to important mineral nutrients such as iron and zinc, forming salts that are largely excreted. This phenomenon can contribute to mineral depletion and deficiency. As one approach to solving this and environmental problems associated with seed-derived dietary phytic acid, the U. S. Department of Agriculture and others have isolated cereal and legume low-phytic acid mutations and have used these to breed first-generation low-phytate hybrids, cultivars and lines of maize (Zea mays), barley (Hordeum vulgare), rice (Oryza sativa) and soybean (Glycine max). Seed phytic acid is reduced in these crops by 50-95%. The progress in the genetics, breeding and nutritional evaluation of low-phytate crops are reviewed in this article.
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Affiliation(s)
- Victor Raboy
- U. S. Department of Agriculture, Agricultural Research Service, National Small Grains Germplasm Research Facility, Aberdeen, ID 83210, USA.
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220
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Hitz WD, Carlson TJ, Kerr PS, Sebastian SA. Biochemical and molecular characterization of a mutation that confers a decreased raffinosaccharide and phytic acid phenotype on soybean seeds. PLANT PHYSIOLOGY 2002; 128:650-60. [PMID: 11842168 PMCID: PMC148927 DOI: 10.1104/pp.010585] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2001] [Revised: 09/20/2001] [Accepted: 10/19/2001] [Indexed: 05/18/2023]
Abstract
A single, recessive mutation in soybean (Glycine max L. Merr.), which confers a seed phenotype of increased inorganic phosphate, decreased phytic acid, and a decrease in total raffinosaccharides, has been previously disclosed (S.A. Sebastian, P.S. Kerr, R.W. Pearlstein, W.D. Hitz [2000] Soy in Animal Nutrition, pp 56-74). The genetic lesion causing the multiple changes in seed phenotype is a single base change in the third base of the codon for what is amino acid residue 396 of the mature peptide encoding a seed-expressed myo-inositol 1-phospate synthase gene. The base change causes residue 396 to change from lysine to asparagine. That amino acid change decreases the specific activity of the seed-expressed myo-inositol 1-phosphate synthase by about 90%. Radio tracer experiments indicate that the supply of myo-inositol to the reaction, which converts UDP-galactose and myo-inositol to galactinol is a controlling factor in the conversion of total carbohydrate into the raffinosaccharides in both wild-type and mutant lines. That same decrease in myo-inositol 1-phosphate synthetic capacity leads to a decreased capacity for the synthesis of myo-inositol hexaphosphate (phytic acid) and a concomitant increase in inorganic phosphate.
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Affiliation(s)
- William D Hitz
- DuPont Crop Genetics, P.O. Box 80402, Wilmington, DE 19880-0402, USA.
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221
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Raboy V. Seeds for a better future: 'low phytate' grains help to overcome malnutrition and reduce pollution. TRENDS IN PLANT SCIENCE 2001; 6:458-62. [PMID: 11590064 DOI: 10.1016/s1360-1385(01)02104-5] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
myo-Inositol(1,2,3,4,5,6)hexakisphosphate (InsP(6) or 'phytic acid') was first known as the storage form of phosphorus in seeds. Seed-derived dietary InsP(6) can contribute to iron and zinc deficiency in human populations. Excretion of 'phytic acid phosphorus' by non-ruminants such as poultry, swine and fish can contribute to water pollution. Sustainable solutions to these important problems might depend on progress in the molecular biology and genetics of InsP(6) accumulation during seed development. The development of 'low phytate' grain and legume genotypes could help advance our understanding of this biology, and when used in foods and feeds might help to reduce human malnutrition and reduce animal waste phosphorus.
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Affiliation(s)
- V Raboy
- US Department of Agriculture, Agricultural Research Service, 1691 So. 2700 W, PO Box 307, Aberdeen, ID 83210, USA.
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222
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Li Y, Ledoux D, Veum T, Raboy V, Zyla K. Low Phytic Acid Barley Improves Performance, Bone Mineralization, and Phosphorus Retention in Turkey Poults. J APPL POULTRY RES 2001. [DOI: 10.1093/japr/10.2.178] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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223
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Hegeman CE, Good LL, Grabau EA. Expression of D-myo-inositol-3-phosphate synthase in soybean. Implications for phytic acid biosynthesis. PLANT PHYSIOLOGY 2001; 125:1941-8. [PMID: 11299373 PMCID: PMC88849 DOI: 10.1104/pp.125.4.1941] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2000] [Revised: 11/13/2000] [Accepted: 01/09/2001] [Indexed: 05/18/2023]
Abstract
Phytic acid, a phosphorylated derivative of myo-inositol, functions as the major storage form of phosphorus in plant seeds. Myo-inositol phosphates, including phytic acid, play diverse roles in plants as signal transduction molecules, osmoprotectants, and cell wall constituents. D-myo-inositol-3-phosphate synthase (MIPS EC 5.5.1.4) catalyzes the first step in de novo synthesis of myo-inositol. A soybean (Glycine max) MIPS cDNA (GmMIPS1) was isolated by reverse transcriptase-PCR using consensus primers designed from highly conserved regions in other plant MIPS sequences. Southern-blot analysis and database searches indicated the presence of at least four MIPS genes in the soybean genome. Northern-blot and immunoblot analyses indicated higher MIPS expression and accumulation in immature seeds than in other soybean tissues. MIPS was expressed early in the cotyledonary stage of seed development. The GmMIPS1 expression pattern suggested that it encodes a MIPS isoform that functions in seeds to generate D-myo-inositol-3-phosphate as a substrate for phytic acid biosynthesis.
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Affiliation(s)
- C E Hegeman
- Department of Plant Pathology, Physiology, and Weed Science, Fralin Biotechnology Center, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0346, USA
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224
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Hatzack F, Hübel F, Zhang W, Hansen PE, Rasmussen SK. Inositol phosphates from barley low-phytate grain mutants analysed by metal-dye detection HPLC and NMR. Biochem J 2001; 354:473-80. [PMID: 11171128 PMCID: PMC1221677 DOI: 10.1042/0264-6021:3540473] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inositol phosphates from barley low-phytate grain mutants and their parent variety were analysed by metal-dye detection HPLC and NMR. Compound assignment was carried out by comparison of retention times using a chemical hydrolysate of phytate [Ins(1,2,3,4,5,6)P(6)] as a reference. Co-inciding retention times indicated the presence of phytate, D/L-Ins(1,2,3,4,5)P(5), Ins(1,2,3,4,6)P(5), D/L-(1,2,4,5,6)P(5), D/L-(1,2,3,4)P(4), D/L-Ins(1,2,5,6)P(4) and D/L-Ins(1,4,5,6)P(4) in PLP1B mutants as well as the parent variety. In grain extracts from mutant lines PLP1A, PLP2A and PLP3A unusual accumulations of D/L-Ins(1,3,4,5)P(4) were observed whereas phytate and the above-mentioned inositol phosphates were present in relatively small amounts. Assignment of D/L-Ins(1,3,4,5)P(4) was corroborated by precise co-chromatography with a commercial Ins(1,3,4,5)P(4) standard and by NMR spectroscopy. Analysis of inositol phosphates during grain development revealed accumulation of phytate and D/L-Ins(1,3,4,5)P(4), which suggested the tetrakisphosphate compound to be an intermediate of phytate synthesis. This assumption was strengthened further by phytate degradation assays showing that D/L-Ins(1,3,4,5)P(4) did not belong to the spectrum of degradation products generated by endogenous phytase activity. Metabolic scenarios leading to accumulation of D/L-Ins(1,3,4,5)P(4) in barley low-phytate mutants are discussed.
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Affiliation(s)
- F Hatzack
- Plant Products and Biomass Recycling Programme, Plant Biology and Biogeochemistry Department, PBK-301, Risø National Laboratory, P.O. Box 49, DK-4000 Roskilde, Denmark
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225
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Li Y, Ledoux D, Veum T, Raboy V, Zyla K, Wikiera A. Bioavailability of Phosphorus in Low Phytic Acid Barley. J APPL POULTRY RES 2001. [DOI: 10.1093/japr/10.1.86] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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