Identification of two Low-Phytate Barley (Hordeum Vulgare l.) Grain Mutants by TLC and Genetic Analysis

Identification of a novel mutation in the OsMRP5 gene in low phytate Basmati rice mutant and development of CAPS marker for marker-assisted breeding

Low phytate level is a desirable trait because it promotes mineral bioavailability and thus offers a solution to tackle mineral deficiencies. The objectives of the present study were to characterize low phytate (lpa) Basmati rice mutants for the identification of novel mutations in target gene(s) and to develop a PCR-based CAPS (cleaved amplified polymorphic sequence) marker for low phytate Basmati rice. For this purpose, cultivar Super Basmati (Q4) was irradiated with gamma rays (60Co source) and three mutants named Q1 (lpa-5-9), Q2 (lpa-9-13), and Q3 (lpa-59-14) were isolated. Four genes previously been reported for the low phytic acid trait in rice were sequenced in these mutants and no mutation was observed in Q1 and Q2. However, in Q3 (lpa14) mutant a novel mutation in OsMRP5 gene (LOC_Os03g04920`) was detected. Sequence analysis displayed a substitution in the first exon of OsMRP5 at position 1142 bp resulting in the amino acid change from glycine (Gly) to alanine (Ala) at position 381a.a. To facilitate low-phytate breeding program, CAPS marker was developed to confirm this mutation site using the restriction digestion by AluI restriction enzyme. After enzyme digestion, Q3 produces four bands (32, 220, 154, and 32 bp) while Q4 (parent cultivar Super Basmati) produces only 3 bands (32, 374, and 32 bp). These results showed that this CAPS marker is 100% linked with this mutation and can be used for future breeding programs. Present findings provided insights in molecular basis of low phytate trait in rice paving the way for developing low-phytate rice varieties through marker-assisted breeding.

Biotechnological approaches to reduce the phytic acid content in millets to improve nutritional quality

MAIN CONCLUSION

The review article summarizes the approaches and potential targets to address the challenges of anti-nutrient like phytic acid in millet grains for nutritional improvement. Millets are a diverse group of minor cereal grains that are agriculturally important, nutritionally rich, and the oldest cereals in the human diet. The grains are important for protein, vitamins, macro and micronutrients, fibre, and energy sources. Despite a high amount of nutrients, millet grains also contain anti-nutrients that limit the proper utilization of nutrients and finally affect their dietary quality. Our study aims to outline the genomic information to identify the target areas of research for the exploration of candidate genes for nutritional importance and show the possibilities to address the presence of anti-nutrient (phytic acid) in millets. So, the physicochemical accessibility of micronutrients increases and the agronomic traits can do better. Several strategies have been adopted to minimize the phytic acid, a predominant anti-nutrient in cereal grains. In the present review, we highlight the potential of biotechnological tools and genome editing approaches to address phytic acid in millets. It also highlights the biosynthetic pathway of phytic acid and potential targets for knockout or silencing to achieve low phytic acid content in millets.

Molecular breeding of barley for quality traits and resilience to climate change

Barley grains are a rich source of compounds, such as resistant starch, beta-glucans and anthocyanins, that can be explored in order to develop various products to support human health, while lignocellulose in straw can be optimised for feed in husbandry, bioconversion into bioethanol or as a starting material for new compounds. Existing natural variations of these compounds can be used to breed improved cultivars or integrated with a large number of mutant lines. The technical demands can be in opposition depending on barley's end use as feed or food or as a source of biofuel. For example beta-glucans are beneficial in human diets but can lead to issues in brewing and poultry feed. Barley breeders have taken action to integrate new technologies, such as induced mutations, transgenics, marker-assisted selection, genomic selection, site-directed mutagenesis and lastly machine learning, in order to improve quality traits. Although only a limited number of cultivars with new quality traits have so far reached the market, research has provided valuable knowledge and inspiration for future design and a combination of methodologies to achieve the desired traits. The changes in climate is expected to affect the quality of the harvested grain and it is already a challenge to mitigate the unpredictable seasonal and annual variations in temperature and precipitation under elevated [CO2] by breeding. This paper presents the mutants and encoded proteins, with a particular focus on anthocyanins and lignocellulose, that have been identified and characterised in detail and can provide inspiration for continued breeding to achieve desired grain and straw qualities.

Study of Seed Ageing in lpa1-1 Maize Mutant and Two Possible Approaches to Restore Seed Germination

Phytic acid (PA) is a strong anti-nutritional factor with a key antioxidant role in countering reactive oxygen species. Despite the potential benefits of low phytic acid (lpa) mutants, the reduction of PA causes pleiotropic effects, e.g., reduced seed germination and viability loss related to seed ageing. The current study evaluated a historical series of naturally aged seeds and showed that lpa1-1 seeds aged faster as compared to wildtype. To mimic natural ageing, the present study set up accelerated ageing treatments at different temperatures. It was found that incubating the seeds at 57 °C for 24 h, the wildtype germinated at 82.4% and lpa1-1 at 40%. The current study also hypothesized two possible solutions to overcome these problems: (1) Classical breeding was used to constitute synthetic populations carrying the lpa1-1 mutation, with genes pushing anthocyanin accumulation in the embryo (R-navajo allele). The outcome showed that the presence of R-navajo in the lpa1-1 genotype was not able to improve the germinability (-20%), but this approach could be useful to improve the germinability in non-mutant genotypes (+17%). (2) In addition, hydropriming was tested on lpa1-1 and wildtype seeds, and germination was improved by 20% in lpa1-1, suggesting a positive role of seed priming in restoring germination. Moreover, the data highlighted metabolic differences in the metabolome before and after hydropriming treatment, suggesting that the differences in germination could also be mediated by differences in the metabolic composition induced by the mutation.

Low Phytate Peas (Pisum sativum L.) Improve Iron Status, Gut Microbiome, and Brush Border Membrane Functionality In Vivo (Gallus gallus)

The inclusion of pulses in traditional wheat-based food products is increasing as the food industry and consumers are recognizing the nutritional benefits due to the high protein, antioxidant activity, and good source of dietary fiber of pulses. Iron deficiency is a significant global health challenge, affecting approximately 30% of the world's population. Dietary iron deficiency is the foremost cause of anemia, a condition that harms cognitive development and increases maternal and infant mortality. This study intended to demonstrate the potential efficacy of low-phytate biofortified pea varieties on dietary iron (Fe) bioavailability, as well as on intestinal microbiome, energetic status, and brush border membrane (BBM) functionality in vivo (Gallus gallus). We hypothesized that the low-phytate biofortified peas would significantly improve Fe bioavailability, BBM functionality, and the prevalence of beneficial bacterial populations. A six-week efficacy feeding (n = 12) was conducted to compare four low-phytate biofortified pea diets with control pea diet (CDC Bronco), as well as a no-pea diet. During the feeding trial, hemoglobin (Hb), body-Hb Fe, feed intake, and body weight were monitored. Upon the completion of the study, hepatic Fe and ferritin, pectoral glycogen, duodenal gene expression, and cecum bacterial population analyses were conducted. The results indicated that certain low-phytate pea varieties provided greater Fe bioavailability and moderately improved Fe status, while they also had significant effects on gut microbiota and duodenal brush border membrane functionality. Our findings provide further evidence that the low-phytate pea varieties appear to improve Fe physiological status and gut microbiota in vivo, and they highlight the likelihood that this strategy can further improve the efficacy and safety of the crop biofortification and mineral bioavailability approach.

Checking Agriculture's Pulse: Field Pea (Pisum Sativum L.), Sustainability, and Phosphorus Use Efficiency

Investigations regarding the incorporation of better sustainable production strategies into current agricultural-food systems are necessary to grow crops that reduce negative impacts on the environment yet will meet the production and nutritional demand of 10 billion people by 2050. The introduction of organic, alternative staple food crops, such as nutrient-dense field pea (Pisum sativum L.), to the everyday diet, may alleviate micronutrient malnutrition and incorporate more sustainable agriculture practices globally. Varieties are grown in organic systems currently yield less than conventionally produced foods, with less bioavailable nutrients, due to poor soil nutrient content. One of the most limiting nutrients for field pea is phosphorus (P) because this legume crop requires significant inputs for nodule formation. Therefore, P use efficiency (PUE) should be a breeding target for sustainable agriculture and biofortification efforts; the important role of the soil microbiome in nutrient acquisition should also be examined. The objectives of this review are to highlight the benefits of field pea for organic agriculture and human health, and discuss nutritional breeding strategies to increase field pea production in organic systems. Field pea and other pulse crops are underrepresented in agricultural research, yet are important crops for a sustainable future and better food systems. Furthermore, because field pea is consumed globally by both developed and at-risk populations, research efforts could help increase global health overall and combat micronutrient malnutrition.

lpa1-5525: A New lpa1 Mutant Isolated in a Mutagenized Population by a Novel Non-Disrupting Screening Method

Phytic acid, or myo-inositol 1,2,3,4,5,6-hexakisphosphate, is the main storage form of phosphorus in plants. It is localized in seeds, deposited as mixed salts of mineral cations in protein storage vacuoles; during germination, it is hydrolyzed by phytases to make available P together with all the other cations needed for seed germination. When seeds are used as food or feed, phytic acid and the bound cations are poorly bioavailable for human and monogastric livestock due to their lack of phytase activity. Therefore, reducing the amount of phytic acid is one strategy in breeding programs aimed to improve the nutritional properties of major crops. In this work, we present data on the isolation of a new maize (Zea mays L.) low phytic acid 1 (lpa1) mutant allele obtained by transposon tagging mutagenesis with the Ac element. We describe the generation of the mutagenized population and the screening to isolate new lpa1 mutants. In particular, we developed a fast, cheap and non-disrupting screening method based on the different density of lpa1 seed compared to the wild type. This assay allowed the isolation of the lpa1-5525 mutant characterized by a new mutation in the lpa1 locus associated with a lower amount of phytic phosphorus in the seeds in comparison with the wild type.

Seed targeted RNAi-mediated silencing of GmMIPS1 limits phytate accumulation and improves mineral bioavailability in soybean

Phytic acid (PA), the major phosphorus reserve in soybean seeds (60-80%), is a potent ion chelator, causing deficiencies that leads to malnutrition. Several forward and reverse genetics approaches have ever since been explored to reduce its phytate levels to improve the micronutrient and phosphorous availability. Transgenic technology has met with success by suppressing the expression of the PA biosynthesis-related genes in several crops for manipulating their phytate content. In our study, we targeted the disruption of the expression of myo-inositol-3-phosphate synthase (MIPS1), the first and the rate limiting enzyme in PA biosynthesis in soybean seeds, by both antisense (AS) and RNAi approaches, using a seed specific promoter, vicilin. PCR and Southern analysis revealed stable integration of transgene in the advanced progenies. The transgenic seeds (T4) of AS (MS14-28-12-29-3-5) and RNAi (MI51-32-22-1-13-6) soybean lines showed 38.75% and 41.34% reduction in phytate levels respectively, compared to non-transgenic (NT) controls without compromised growth and seed development. The electron microscopic examination also revealed reduced globoid crystals in the Protein storage vacoules (PSVs) of mature T4 seeds compared to NT seed controls. A significant increase in the contents of Fe2+ (15.4%, 21.7%), Zn2+ (7.45%, 11.15%) and Ca2+ (10.4%, 15.35%) were observed in MS14-28-12-29-3-5 and MI51-32-22-1-13-6 transgenic lines, respectively, compared to NT implicating improved mineral bioavailability. This study signifies proof-of-concept demonstration of seed-specific PA reduction and paves the path towards low phytate soybean through pathway engineering using the new and precise editing tools.

Development and Evaluation of Low Phytic Acid Soybean by siRNA Triggered Seed Specific Silencing of Inositol Polyphosphate 6-/3-/5-Kinase Gene

Soybean is one of the leading oilseed crop in the world and is showing a remarkable surge in its utilization in formulating animal feeds and supplements. Its dietary consumption, however, is incongruent with its existing industrial demand due to the presence of anti-nutritional factors in sufficiently large amounts. Phytic acid in particular raises concern as it causes a concomitant loss of indigestible complexed minerals and charged proteins in the waste and results in reduced mineral bioavailability in both livestock and humans. Reducing the seed phytate level thus seems indispensable to overcome the nutritional menace associated with soy grain consumption. In order to conceive our objective we designed and expressed a inositol polyphosphate 6-/3-/5-kinase gene-specific RNAi construct in the seeds of Pusa-16 soybean cultivar. We subsequently conducted a genotypic, phenotypic and biochemical analysis of the developed putative transgenic populations and found very low phytic acid levels, moderate accumulation of inorganic phosphate and elevated mineral content in some lines. These low phytic acid lines did not show any reduction in seedling emergence and displayed an overall good agronomic performance.

Phytic acid transport in Phaseolus vulgaris: A new low phytic acid mutant in the PvMRP1 gene and study of the PvMRPs promoters in two different plant systems

Phytic acid (InsP₆) is the main storage form of phosphate in seeds. In the plant it plays an important role in response to environmental stress and hormonal changes. InsP₆ is a strong chelator of cations, reducing the bioavailability of essential minerals in the diet. Only a common bean low phytic acid (lpa1) mutant, affected in the PvMRP1 gene, coding for a putative tonoplastic phytic acid transporter, was described so far. This mutant is devoid of negative pleiotropic effects normally characterising lpa mutants. With the aim of isolating new common bean lpa mutants, an ethyl methane sulfonate mutagenized population was screened, resulting in the identification of an additional lpa1 allele. Other putative lpa lines were also isolated. The PvMRP2 gene is probably able to complement the phenotype of mutants affected in the PvMRP1 gene in tissues other than the seed. Only the PvMRP1 gene is expressed at appreciable levels in cotyledons. Arabidopsis thaliana and Medicago truncatula transgenic plants harbouring 1.5 kb portions of the intergenic 5' sequences of both PvMRP genes, fused upstream of the GUS reporter, were generated. GUS activity in different organs suggests a refined, species-specific mechanisms of regulation of gene expression for these two PvMRP genes.

Genetic Basis and Breeding Perspectives of Grain Iron and Zinc Enrichment in Cereals

Micronutrient deficiency, also known as "hidden hunger," is an increasingly serious global challenge to humankind. Among the mineral elements, Fe (Iron) and Zn (Zinc) have earned recognition as micronutrients of outstanding and diverse biological relevance, as well as of clinical importance to global public health. The inherently low Fe and Zn content and poor bioavailability in cereal grains seems to be at the root of these mineral nutrient deficiencies, especially in the developing world where cereal-based diets are the most important sources of calories. The emerging physiological and molecular understanding of the uptake of Fe and Zn and their translocation in cereal grains regrettably also indicates accumulation of other toxic metals, with chemically similar properties, together with these mineral elements. This review article emphasizes breeding to develop bioavailable Fe- and Zn-efficient cereal cultivars to overcome malnutrition while minimizing the risks of toxic metals. We attempt to critically examine the genetic diversity regarding these nutritionally important traits as well as the progress in terms of quantitative genetics. We sought to integrate findings from the rhizosphere with Fe and Zn accumulation in grain, and to discuss the promoters as well as the anti-nutritional factors affecting Fe and Zn bioavailability in humans while restricting the content of toxic metals.

The Challenges and Opportunities Associated with Biofortification of Pearl Millet (Pennisetum glaucum) with Elevated Levels of Grain Iron and Zinc

Deficiencies of essential micronutrients such as iron and zinc are the cause of extensive health problems in developing countries. They adversely affect performance, productivity and are a major hindrance to economic development. Since many people who suffer from micronutrient deficiencies are dependent on staple crops to meet their dietary requirements, the development of crop cultivars with increased levels of micronutrients in their edible parts is becoming increasingly recognized as a sustainable solution. This is largely facilitated by genetics and genomic platforms. The cereal crop pearl millet (Pennisetum glaucum), is an excellent candidate for genetic improvement due to its ability to thrive in dry, semi-arid regions, where farming conditions are often unfavorable. Not only does pearl millet grow in areas where other crops such as maize and wheat do not survive, it contains naturally high levels of micronutrients, proteins and a myriad of other health benefitting characteristics. This review discusses the current status of iron and zinc deficiencies and reasons why interventions such as fortification, supplementation, and soil management are neither practicable nor affordable in poverty stricken areas. We argue that the most cost effective, sustainable intervention strategy is to biofortify pearl millet with enhanced levels of bioavailable iron and zinc. We discuss how naturally occurring genetic variations present in germplasm collections can be incorporated into elite, micronutrient rich varieties and what platforms are available to drive this research. We also consider the logistics of transgenic methods that could facilitate the improvement of the pearl millet gene pool.

Low-phytic-acid Grains

As one approach to the improvement of the nutritional quality of crops for both foods and feeds, low-phytic-acid (lpa) mutants of maize and other cereals have been isolated. An important advantage of lpa mutants is that the bioavailability of a range of minerals may be improved, although phytic acid can also function as an antioxidant. Livestock producers are primarily concerned with excretion of feed phytic acid phosphorus by livestock and fish. This contributes to water pollution and is a major environmental issue in developed countries. In these mutants, phytic acid phosphorus is reduced by 55% to 66%, which is matched by an equal increase in inorganic phosphorus. Greater reductions in phytic acid, as high as 95% to 99%, may be desirable and are possible. The first two studies of an lpa maize in human nutrition found increased fractional absorption of iron and zinc in the lpa maize as compared with the control maize.

Yields of the best lpa lines, first developed in the mid-1990s, now range between 5% and 15% below those of the highest-yielding commercial varieties. Because of benefits for animal nutrition, lpa crops could become highly profitable for use as animal feeds. All lpa lines to date have been developed using classical genetic methods; these classically obtained mutants affect the expression of a given gene throughout the tissues and organs of a plant. BY using a biotechnology approach, it may be possible to achieve optimal levels of phytic acid reduction and target the desired effect to the seed, thereby reducing any undesirable agronomic effects of whole-plant mutants.

A decrease in phytic acid content substantially affects the distribution of mineral elements within rice seeds

Phytic acid (myo-inositol hexakisphosphate; InsP6) is the storage compound of phosphorus and many mineral elements in seeds. To determine the role of InsP6 in the accumulation and distribution of mineral elements in seeds, we performed fine mappings of mineral elements through synchrotron-based X-ray microfluorescence analysis using developing seeds from two independent low phytic acid (lpa) mutants of rice (Oryza sativa L.). The reduced InsP6 in lpa seeds did not affect the translocation of mineral elements from vegetative organs into seeds, because the total amounts of phosphorus and the other mineral elements in lpa seeds were identical to those in the wild type (WT). However, the reduced InsP6 caused large changes in mineral localization within lpa seeds. Phosphorus and potassium in the aleurone layer of lpa greatly decreased and diffused into the endosperm. Zinc and copper, which were broadly distributed from the aleurone layer to the inner endosperm in the WT, were localized in the narrower space around the aleurone layer in lpa mutants. We also confirmed that similar distribution changes occurred in transgenic rice with the lpa phenotype. Using these results, we discussed the role of InsP6 in the dynamic accumulation and distribution patterns of mineral elements during seed development.

Accumulation of Phosphorus-Containing Compounds in Developing Seeds of Low-Phytate Pea (Pisum sativum L.) Mutants

Low phytic acid (lpa) crops are low in phytic acid and high in inorganic phosphorus (Pi). In this study, two lpa pea genotypes, 1-150-81, 1-2347-144, and their progenitor CDC Bronco were grown in field trials for two years. The lpa genotypes were lower in IP₆ and higher in Pi when compared to CDC Bronco. The total P concentration was similar in lpa genotypes and CDC Bronco throughout the seed development. The action of myo-inositol phosphate synthase (MIPS) (EC 5.5.1.4) is the first and rate-limiting step in the phytic acid biosynthesis pathway. Aiming at understanding the genetic basis of the lpa mutation in the pea, a 1530 bp open reading frame of MIPS was amplified from CDC Bronco and the lpa genotypes. Sequencing results showed no difference in coding sequence in MIPS between CDC Bronco and lpa genotypes. Transcription levels of MIPS were relatively lower at 49 days after flowering (DAF) than at 14 DAF for CDC Bronco and lpa lines. This study elucidated the rate and accumulation of phosphorus compounds in lpa genotypes. The data also demonstrated that mutation in MIPS was not responsible for the lpa trait in these pea lines.

Phosphate and zinc transport and signalling in plants: toward a better understanding of their homeostasis interaction

Inorganic phosphate (Pi) and zinc (Zn) are two essential nutrients for plant growth. In soils, these two minerals are either present in low amounts or are poorly available to plants. Consequently, worldwide agriculture has become dependent on external sources of Pi and Zn fertilizers to increase crop yields. However, this strategy is neither economically nor ecologically sustainable in the long term, particularly for Pi, which is a non-renewable resource. To date, research has emphasized the analysis of mineral nutrition considering each nutrient individually, and showed that Pi and Zn homeostasis is highly regulated in a complex process. Interestingly, numerous observations point to an unexpected interconnection between the homeostasis of the two nutrients. Nevertheless, despite their fundamental importance, the molecular bases and biological significance of these interactions remain largely unknown. Such interconnections can account for shortcomings of current agronomic models that typically focus on improving the assimilation of individual elements. Here, current knowledge on the regulation of the transport and signalling of Pi and Zn individually is reviewed, and then insights are provided on the recent progress made towards a better understanding of the Zn-Pi homeostasis interaction in plants.

Combating Mineral Malnutrition through Iron and Zinc Biofortification of Cereals

 Iron and zinc are 2 important nutrients in the human diet. Their deficiencies in humans lead to a variety of health-related problems. Iron and zinc biofortification of cereals is considered a cost-effective solution to overcome the malnutrition of these minerals. Biofortification aims at either increasing accumulation of these minerals in edible parts, endosperm, or to increase their bioavailability. Iron and zinc fertilization management positively influence their accumulation in cereal grains. Regarding genetic strategies, quantitative genetic studies show the existence of ample variation for iron and zinc accumulation as well as inhibitors or promoters of their bioavailability in cereal grains. However, the genes underlying this variation have rarely been identified and never used in breeding programs. Genetically modified cereals developed by modulation of genes involved in iron and zinc homeostasis, or genes influencing bioavailability, have shown promising results. However, iron and zinc concentration were quantified in the whole grains during most of the studies, whereas a significant proportion of them is lost during milling. This makes it difficult to realistically assess the effectiveness of the different strategies. Moreover, modifications in the accumulation of toxic elements, like cadmium and arsenic, that are of concern for food safety are rarely determined. Trials in living organisms with iron- and zinc-biofortified cereals also remain to be undertaken. This review focuses on the common challenges and their possible solutions related to agronomic as well as genetic iron and zinc biofortification of cereals.

Low phytic acid 1 mutation in maize modifies density, starch properties, cations, and fiber contents in the seed

Monogastric animals are unable to digest phytic acid, so it represents an antinutritional factor and also an environmental problem. One strategy to solve this problem is the utilization of low phytic acid (lpa) mutants that accumulate low levels of phytic P and high levels of free phosphate in the seeds; among the lpa maize mutants lpa1 exhibited the highest reduction of phytic acid in the seed. This study indicated that the low phytic acid mutations exerted pleiotropic effects not directly connected to the phytic acid pathway, such as on seed density, content of ions, and the antioxidant compounds present in the kernels. Furthermore some nutritional properties of the flour were altered by the lpa1 mutations, in particular lignin and protein content, while the starch does not seem to be modified as to the total amount and in the amylose/amylopectin ratio, but alterations were noticed in the structure and size of granules.

Functions of ABC transporters in plants

ABC (ATP-binding cassette) proteins are ubiquitously found in prokaryotes and eukaryotes and generally serve as membrane-intrinsic primary active pumps. In higher plants, ABC proteins constitute a large family, grouped phylogenetically into eight clusters, subfamilies ABCA-ABCI (ABCH is not found in plants). ABC transporters shuttle substrates as diverse as lipids, phytohormones, carboxylates, heavy metals, chlorophyll catabolites and xenobiotic conjugates across a variety of biological membranes. To date, the largest proportions of characterized members have been localized to the plasma membrane and the tonoplast, with dominant implications in cellular secretion and vacuolar sequestration, but they are also found in mitochondrial, plastidal and peroxisomal membranes. Originally identified as tonoplast-intrinsic proteins that shuttle xenobiotic conjugates from the cytosol into the vacuole, thus being an integral part of the detoxification machinery, ABC transporters are now recognized to participate in a multitude of physiological processes that allow the plant to adapt to changing environments and cope with biotic and abiotic stresses.

Mutations in genes controlling the biosynthesis and accumulation of inositol phosphates in seeds

Most of the phosphorus in the resting seed is stored inside protein storage vacuoles as PA (phytic acid; InsP(6)). The biosynthesis and accumulation of PA can be detected beginning from a few days after anthesis and seem to continue during seed development until maturation. The first step in PA biosynthesis is the formation of Ins3P by conversion of glucose 6-phosphate. This is then followed by a sequential and ordered phosphorylation of the remaining five positions of the inositol ring by a number of kinases, resulting in PA. Identification of low-PA mutants in cereals, legumes and Arabidopsis is instrumental for resolving the biosynthetic pathway and identification of genes controlling the accumulation of PA. Mutations in seven genes involved in the metabolism of PA have been identified and characterized among five plant species using induced mutagenesis and insertion elements. Understanding the biosynthetic pathway and genes controlling the accumulation of PA in plant seeds and how PA may balance the free phosphate is of importance for molecular breeding of crop plants, particularly cereals and legumes.

The low phytic acid1-241 (lpa1-241) maize mutation alters the accumulation of anthocyanin pigment in the kernel

The lpa1 mutations in maize are caused by lesions in the ZmMRP4 (multidrug resistance-associated proteins 4) gene. In previous studies (Raboy et al. in Plant Physiol 124:355-368, 2000; Pilu et al. in Theor Appl Genet 107:980-987, 2003a; Shi et al. Nat Biotechnol 25:930-937, 2007), several mutations have been isolated in this locus causing a reduction of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, or InsP(6)) content and an equivalent increasing of free phosphate. In particular, the lpa1-241 mutation causes a reduction of up to 90% of phytic acid, associated with strong pleiotropic effects on the whole plant. In this work, we show, for the first time to our knowledge, an interaction between the accumulation of anthocyanin pigments in the kernel and the lpa mutations. In fact the lpa1-241 mutant accumulates a higher level of anthocyanins as compared to wild type either in the embryo (about 3.8-fold) or in the aleurone layer (about 0.3-fold) in a genotype able to accumulate anthocyanin. Furthermore, we demonstrate that these pigments are mislocalised in the cytoplasm, conferring a blue pigmentation of the scutellum, because of the neutral/basic pH of this cellular compartment. As a matter of fact, the propionate treatment, causing a specific acidification of the cytoplasm, restored the red pigmentation of the scutellum in the mutant and expression analysis showed a reduction of ZmMRP3 anthocyanins' transporter gene expression. On the whole, these data strongly suggest a possible interaction between the lpa mutation and anthocyanin accumulation and compartmentalisation in the kernel.

Generation of stable 'low phytic acid' transgenic rice through antisense repression of the 1D-myo-inositol 3-phosphate synthase gene (RINO1) using the 18-kDa oleosin promoter

Phytic acid acts as the major storage form of phosphorus in plant seeds and is poorly digested by monogastric animals. The degradation of phytic acid in animal diets is necessary to overcome both environmental and nutritional issues. The enzyme 1D-myo-inositol 3-phosphate [Ins(3)P(1)] synthase (EC 5.5.1.4) catalyses the first step of myo-inositol biosynthesis and directs phytic acid biosynthesis in seeds. The rice Ins(3)P(1) synthase gene (RINO1) is highly expressed in developing seed embryos and in the aleurone layer, where phytic acid is synthesized and stored. In rice seeds, 18-kDa oleosin (Ole18) is expressed in a seed-specific manner, and its transcripts are restricted to the embryo and the aleurone layer. Therefore, to effectively suppress phytic acid biosynthesis, antisense RINO1 cDNA was expressed under the control of the Ole18 promoter, directing the same spatial pattern in seeds as RINO1 in transgenic rice plants. The generated transgenic rice plants showed strong 'low phytic acid' (lpa) phenotypes, in which seed phytic acid was reduced by 68% and free available phosphate was concomitantly increased. No negative effects on seed weight, germination or plant growth were observed. The available phosphate levels of the stable transgenic plants surpassed those of currently available rice lpa mutants.

A role for inositol hexakisphosphate in the maintenance of basal resistance to plant pathogens

Phytic acid (myo-inositol hexakisphosphate, InsP6) is an important phosphate store and signal molecule in plants. However, low-phytate plants are being developed to minimize the negative health effects of dietary InsP6 and pollution caused by undigested InsP6 in animal waste. InsP6 levels were diminished in transgenic potato plants constitutively expressing an antisense gene sequence for myo-inositol 3-phosphate synthase (IPS, catalysing the first step in InsP6 biosynthesis) or Escherichia coli polyphosphate kinase. These plants were less resistant to the avirulent pathogen potato virus Y and the virulent pathogen tobacco mosaic virus (TMV). In Arabidopsis thaliana, mutation of the gene for the enzyme catalysing the final step of InsP6 biosynthesis (InsP5 2-kinase) also diminished InsP6 levels and enhanced susceptibility to TMV and to virulent and avirulent strains of the bacterial pathogen Pseudomonas syringae. Arabidopsis thaliana has three IPS genes (AtIPS1-3). Mutant atips2 plants were depleted in InsP6 and were hypersusceptible to TMV, turnip mosaic virus, cucumber mosaic virus and cauliflower mosaic virus as well as to the fungus Botrytis cinerea and to P. syringae. Mutant atips2 and atipk1 plants were as hypersusceptible to infection as plants unable to accumulate salicylic acid (SA) but their increased susceptibility was not due to reduced levels of SA. In contrast, mutant atips1 plants, which were also depleted in InsP6, were not compromised in resistance to pathogens, suggesting that a specific pool of InsP6 regulates defence against phytopathogens.

The rice OsLpa1 gene encodes a novel protein involved in phytic acid metabolism

The rice low phytic acid 1 (lpa1) mutant was originally identified using a forward genetics approach. This mutant exhibits a 45% reduction in rice seed phytic acid with a molar-equivalent increase in inorganic phosphorus; however, it does not appear to differ significantly in productivity from its wild-type progenitor. A second lpa1 mutant was identified from additional screening for high seed inorganic phosphorus phenotypes. Using a positional cloning strategy, we identified a single candidate gene at the rice Lpa1 locus. Sequence analysis of the candidate gene from the lpa1 mutants revealed two independent mutations (a single base pair substitution and a single base pair deletion) that confirmed the identification of this candidate as the rice low phytic acid 1 gene, OsLpa1. The OsLpa1 gene has three splice variants. The location and nature of the two mutations suggests that these lesions only affect the translation of the predicted protein derived from the longest transcript. The proteins encoded by OsLpa1 do not have homology to any of the inositol phosphate metabolism genes recently characterized in plants, although there is homology to 2-phosphoglycerate kinase, an enzyme found in hyperthermophilic methanogens that catalyzes the formation of 2,3-bisphosphoglycerate from 2-phosphoglycerate. OsLpa1 represents a novel gene involved in phytic acid metabolism.

Expression pattern of inositol phosphate-related enzymes in rice (Oryza sativa L.): implications for the phytic acid biosynthetic pathway

Phytic acid, myo-inositol-hexakisphosphate (InsP(6)), is a storage form of phosphorus in plants. Despite many physiological investigations of phytic acid accumulation and storage, little is known at the molecular level about its biosynthetic pathway in plants. Recent work has suggested two pathways. One is an inositol lipid-independent pathway that occurs through the sequential phosphorylation of 1D-myo-inositol 3-phosphate (Ins(3)P). The second is a phospholipase C (PLC)-mediated pathway, in which inositol 1,4,5-tris-phosphate (Ins(1,4,5)P(3)) is sequentially phosphorylated to InsP(6). We identified 12 genes from rice (Oryza sativa L.) that code for the enzymes that may be involved in the metabolism of inositol phosphates. These enzymes include 1D-myo-inositol 3-phosphate synthase (MIPS), inositol monophosphatase (IMP), inositol 1,4,5-tris-phosphate kinase/inositol polyphosphate kinase (IPK2), inositol 1,3,4,5,6-pentakisphosphate 2-kinase (IPK1), and inositol 1,3,4-triskisphosphate 5/6-kinase (ITP5/6K). The quantification of absolute amounts of mRNA by real-time RT-PCR revealed the unique expression patterns of these genes. Outstanding up-regulation of the four genes, a MIPS, an IPK1, and two ITP5/6Ks in embryos, suggested that they play a significant role in phytic acid biosynthesis and that the lipid-independent pathway was mainly active in developing seeds. On the other hand, the up-regulation of a MIPS, an IMP, an IPK2, and an ITP5/6K in anthers suggested that a PLC-mediated pathway was active in addition to a lipid-independent pathway in the anthers.

Characterization of a multifunctional inositol phosphate kinase from rice and barley belonging to the ATP-grasp superfamily

OsIpk and HvIpk, inositol phosphate kinases, were cloned from rice (Oryza sativa L. var. indica, IR64) and barley (Hordeum vulgare) respectively. Sequence alignment showed that they belong to the ATP-grasp family, which includes inositol 1,3,4-trisphosphate 5/6-kinase from humans and Arabidopsis. Residues that are binding sites for ATP and coordinate magnesium in absence or presence of inositol phosphate are conserved and in total 23 residues are invariant among the twelve aligned inositol phosphate kinases. The genes were heterologously expressed in Escherichia coli and kinase activity assays with 17 different isomers of inositol mono-/di-/tri-/tetra-/pentaphosphate as well as phytate were performed. The strongest activity for both kinases was observed with Ins(3,4,5,6)P(4), which candidates as the primary substrate for these kinases in plants. Several species-specific differences between the two recombinant Ipks were observed. Rice OsIpk showed detectable kinase activity towards eight different substrates, whereas barley HvIpk showed kinase activity with all the substrates including inositol mono- and bisphosphates. HvIpk showed 3-kinase activity towards the Ins(1,4,5)P(3) substrate and it also interconverted the two substrates Ins(1,3,4,5)P(4) and Ins(1,3,4,6)P(4) by isomerase activity, which was not observed for the rice homologue. Both OsIpk and HvIpk had no detectable 2-kinase activity. Furthermore, the two Ipks showed phosphatase activity towards several inositol phosphates. Expression analysis by RT-PCR demonstrated that the Ipk gene was equally expressed in different tissues and developmental stages. Taken together, these results show that the Ipk kinase plays a significant role in the inositol phosphate interacting network in plants.

Generation and characterization of low phytic acid germplasm in rice (Oryza sativa L.)

Phytic acid (PA, myo-inositol 1,2,3,4,5,6-hexakisphosphate), or its salt form, phytate, is commonly regarded as the major anti-nutritional component in cereal and legume grains. Breeding of low phytic acid (lpa) crops has recently been considered as a potential way to increase nutritional quality of crop products. In this study, eight independent lpa rice mutant lines from both indica and japonica subspecies were developed through physical and chemical mutagenesis. Among them, five are non-lethal while the other three are homozygous lethal. None of the lethal lines could produce homozygous lpa plants through seed germination and growth under field conditions, but two of them could be rescued through in vitro culture of mature embryos. The non-lethal lpa mutants had lower PA content ranging from 34 to 64% that of their corresponding parent and four of them had an unchanged total P level. All the lpa mutations were inherited in a single recessive gene model and at least four lpa mutations were identified mutually non-allelic, while the other two remain to be verified. One mutation was mapped on chromosome 2 between microsatellite locus RM3542 and RM482, falling in the same region as the previously mapped lpa1-1 locus did; another lpa mutation was mapped on chromosome 3, tightly linked to RM3199 with a genetic distance of 1.198 cM. The latter mutation was very likely to have happened to the LOC_Os03g52760, a homolog of the maize myo-inositol kinase (EC 2.7.1.64) gene. The present work greatly expands the number of loci that could influence the biosynthesis of PA in rice, making rice an excellent model system for research in this area.

Low-phytate barley cultivars improve the utilization of phosphorus, calcium, nitrogen, energy, and dry matter in diets fed to young swine

A 28-d experiment was conducted using 45 crossbred barrows with an average initial BW of 9.5 kg and age of 35 d to evaluate low-phytate barley (LPB) mutants (M) M422, M635, and M955, which were hulled, near-isogenic progeny of the normal barley (NB) Harrington and had 47, 66, and 80% less phytic acid, respectively, than NB. A hull-less LPB, M422-H, which was not near-isogenic to the other cultivars, was also evaluated. Apparent nutrient balance, bone measurements, and growth performance were the response criteria evaluated. The barrows were fed the diets to appetite in meal form in individual metabolism crates. Barley and soybean meal were the only sources of phytic acid. Dietary protein supplementation and ME/kg were equalized in all diets. The treatments were diets containing NB, M422, M635, or M422-H without or with added inorganic P (iP), or M955 without added iP. Diets with added iP contained 0.30% available P (aP), the same concentration of aP provided by the diet containing M955 without added iP. There were linear increases (P < or = 0.02) in ADG, G:F, metacarpal and radius bone strength, and fat-free dry weight, and in the absorption and retention (g/d and % of intake) of P and Ca with increasing dietary concentration of aP from the near-isogenic cultivars NB, M422, M635, or M955 without added iP. There were linear decreases in the grams (P < or = 0.02) and percentages (P < 0.001) of P and Ca excreted per day with increasing dietary concentration of aP without added iP. There were no responses for N or energy balance. Growth performance and bone response criteria did not differ for barrows fed the diet containing M955 or the near-isogenic diets containing NB, M422, or M635 with added iP. However, barrows fed the diet containing M955 had greater (P < or = 0.02) percentages of P, N, and energy absorption and retention, Ca absorption, and DM digestibility and had less (P < or = 0.02, g/d and %) excretion of P, N, energy, and Ca (g) per day than barrows fed the diets containing the near-isogenic NB or LPB cultivars with added iP. When dietary aP was equalized with iP, the excretion of P in feces plus urine (g/d) was reduced by 20.2, 27.9, and 44.6%, respectively, in barrows fed the diets containing M422 + iP, M635 + iP, or M955 compared with barrows fed the diet containing NB + iP. Energy utilization did not differ for barrows fed the diets containing hulled or hull-less LPB when ME/kg was equalized with lard. In conclusion, the apparent utilization of P and Ca, the bone strength and fat-free dry weight, and growth performance increased with increasing dietary concentration of aP provided by LPB, in association with linear decreases in P and Ca excretion. Barrows fed the diet containing M955 also had greater utilization and less excretion of P, Ca, N, energy, and DM than barrows fed the diets containing the near-isogenic NB or LPB cultivars with added iP to equalize aP at 0.30%.

Calcium, phosphorus, and amino acid digestibility in low-phytate corn, normal corn, and soybean meal by growing pigs

Nine growing barrows were equipped with a T-cannula in the distal ileum and used to determine apparent ileal (AID) and apparent total-tract digestibility (ATTD) coefficients of Ca and P in low-phytate corn, normal corn, soybean meal, and in diets where soybean meal was mixed with low-phytate corn or normal corn. The AID and the standardized ileal digestibility coefficients (SID) of CP and AA also were determined. The animals (initial BW = 29.3 +/- 1 kg) were allotted to a 9 x 9 Latin square with nine diets and nine periods. Three diets contained low-phytate corn, normal corn, and soybean meal as their sole source of CP, AA, Ca, and P, respectively. Three additional diets were identical to these diets except that limestone and monosodium phosphate were added. Two diets contained low-phytate corn or normal corn and soybean meal, limestone, and monosodium phosphate, and the final diet was a N-free diet. The AID and ATTD of Ca were higher (P < 0.05) for low-phytate corn than for normal corn (70.0 and 69.1% vs. 47.4 and 49.6%, respectively). The AID and ATTD for Ca in soybean meal (50.9 and 46.7%, respectively) did not differ from values for normal corn but were lower (P < 0.05) than for low-phytate corn. The AID and ATTD for P from low-phytate corn (56.5 and 54.5%, respectively) were greater (P < 0.05) than from normal corn (28.3 and 28.8%, respectively), whereas soybean meal had intermediate AID and ATTD for P (37.2 and 38.0%, respectively). The AID and ATTD of P increased (P < 0.05) when monosodium phosphate was added to normal corn (44.9 and 49.8%, respectively) and soybean meal (49.6 and 46.2%, respectively), but adding monosodium phosphate to low-phytate corn, did not alter either AID (49.7%) or ATTD (50.7%) of P. No differences between AID and ATTD for Ca or P within the same diet were observed. The AID of Arg, Asp, Gly, Ile, Lys, Phe, Thr, and Val were greater (P < 0.05) in low-phytate corn than in normal corn. The AID of all AA in soybean meal were greater (P < 0.05) than in both types of corn, with the exception of Ala, Cys, Leu, and Met. The SID of Lys, Phe, and Thr were higher (P < 0.05) in low-phytate corn than in normal corn. Because low-phytate corn has a higher digestibility of Ca and P, less inorganic Ca and P need to be supplemented to diets containing low-phytate corn than to those containing normal corn, and P excretion may be decreased when low-phytate corn is used in the diet.

Fine mapping of the rice low phytic acid (Lpa1) locus

Phytic acid is the primary storage form of phosphorus (P) in cereal grains. In addition to being essential for normal seedling growth and development, phytic acid plays an important role in human and animal nutrition. The rice low phytic acid mutation lpa1 results in a 45% reduction in seed phytic acid with a molar equivalent increase in inorganic P. The Lpa1 locus was previously mapped to the long arm of chromosome 2. Using microsatellite markers and a recombinant inbred line population, we fine mapped this locus between the markers RM3542 and RM482, which encompass a region of 135 kb. Additional markers were developed from the DNA sequence of this region. Two of these markers further delimited the locus to a 47-kb region containing eight putative open reading frames. Cloning and molecular characterization of the Lpa1 gene will provide insight into phytic acid biosynthesis in plants. The markers reported here should also be useful in introgressing the low phytic acid phenotype into other rice cultivars.

The concentrations and distribution of phytic acid-phosphorus and other mineral nutrients in wild-type and low phytic acid1-1 (lpa1-1) corn (Zea mays L.) grains and grain parts

A comparison of mineral nutrient and phytic acid-phosphorus (PA-P) distribution in the grains of wild-type (WT) and low phytic acid1-1 (lpa1-1) corn (Zea mays L.) was conducted to determine how the lpa1-1 mutation influences mineral element concentrations in different grain parts and impacts the structure of phosphorus-rich inclusions (globoids) in the grain cells. This is the first report regarding total phosphorus (P) and PA-P concentrations in scutellum and root-shoot axis portions of cereal embryos of WT in comparison to its matching lpa1-1 genotype. In WT, 95% of the grain PA-P was located in the embryo, mostly in the scutellum. The lpa1-1 mutation reduced whole-grain PA-P by 62% but influenced the scutella more than the root-shoot axes and rest-of-grain fractions. In spite of the lpa1-1 mutants containing greatly reduced PA-P, whole-grain amounts of Mg, Fe, and Mn were higher in lpa1-1 than in WT, K and Zn were similar, and Ca was lower. Iron was 1/3 higher in lpa1-1 grains than WT while Ca was 18% lower. Decreased phytic acid in lpa1-1 grains resulted in reduction in globoid size in both scutellum and aleurone layer cells. Most lpa1-1 aleurone globoids were non-spherical and scutellum globoids were clusters of small spheres while WT globoids were large discrete spheres. X-ray analyses of globoids in both grain types revealed major amounts of P, K, and Mg and traces of Ca, Fe, and Zn. Both grain types contained almost no mineral nutrient stores in the starchy endosperm.Key words: corn (Zea mays L.), phytic acid-phosphorus, low phytic acid1-1 (lpa1-1) grains, mineral nutrients, globoids, electron microscopy.

Phenotypic, genetic and molecular characterization of a maize low phytic acid mutant (lpa241)

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.

Seed phosphorus and inositol phosphate phenotype of barley low phytic acid genotypes

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.

The maize low-phytic acid mutant lpa2 is caused by mutation in an inositol phosphate kinase gene

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.

Progress in breeding low phytate crops

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.