Special Issue "Phytic Acid Pathway and Breeding in Plants"

A special issue of Plants (ISSN 2223-7747).

Deadline for manuscript submissions: closed (28 February 2015).

Special Issue Editors

Dr. Francesca Sparvoli
E-Mail Website
Guest Editor
Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy
Interests: legumes; Phaseolus vulgaris; seed; seed protein; seed nutritional quality; phytic acid metabolism; ABC-MRP type phytic acid transporter; lpa mutants
Special Issues and Collections in MDPI journals
Dr. Roberto Pilu
E-Mail Website
Guest Editor
Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia Università degli Studi di Milano, Milano, Italy
Interests: Poaceae; Zea mays; genetic improvement; seed nutritional quality; phytic acid; lpa mutants; ABC-MRP type phytic acid transporter
Special Issues and Collections in MDPI journals
Dr. Eleonora Cominelli
E-Mail Website
Guest Editor
Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy
Interests: seed nutritional quality; phytic acid metabolism; ABC-MRP type phytic acid transporter; lpa mutants; abiotic stresses; mineral accumulation
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Phytic acid is the main storage form for phosphate in plant seeds. From a nutritional point of view, it decreases the seed value by chelating important minerals, such as iron, zinc, magnesium, and calcium. Therefore, the isolation of low phytic acid (lpa) mutants is considered a highly desirable objective in the genetic improvement of the nutritional quality of grain crops. On the other hand, phytic acid is a very important signaling molecule involved in development and hormonal regulation. lpa mutants often display a general perturbation of the different branches of phytic acid and of other linked compounds and precursor (galactinol, raffinose, stachyose, ascorbic acid, myo-inositol) biosynthetic pathways, suggesting connections with the phosphoinositide signaling pathway. As a consequence, many important agronomic traits in lpa plants are affected.

Indications exist that phytic acid itself and enzymes involved in its biosynthetic pathway (such as MIPS, IPK1, IPK2), may have a nuclear localization and thus may exert roles in the regulation of several nuclear processes (mRNA export from the nucleus, chromatin remodeling, telomere length). Considering the key role phytic acid plays in plant health and human nutrition, a deeper knowledge of phytic acid synthesis and regulation is mandatory in order to be able to tailor productive lpa crops.

This Special Issue aims to provide a unique compendium that highlights new developments in our understanding of how perturbation in phytic acid synthesis and accumulation contributes to plant function, growth, and response to the environment. Contributions to this Special Issue are invited from scientists working at all system levels, including from the molecule, cell, organism and environment/ecological perspectives.

Furthermore contributions from breeders concerning development, studies and utilization of genetically improved materials (lpa) will be welcomed.

Studies addressing any of the above aspects of phytic acid synthesis and accumulation would be appropriate contributions.

Dr. Francesca Sparvoli
Dr. Roberto Pilu
Dr. Eleonora Cominelli
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Plants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • myo-inositol
  • inositol phosphate
  • inositol hexakisphosphate
  • inositol kinases
  • inositol 1,4,5-trisphosphate
  • ABC transporter
  • inositol polyphosphate phosphatase
  • hormone receptor
  • low phytic acid (lpa) mutants
  • seed development
  • signal transduction
  • Ca2+
  • ABA, Auxin

Published Papers (7 papers)

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Research

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Article
Hormonal Regulation and Expression Profiles of Wheat Genes Involved during Phytic Acid Biosynthesis Pathway
Plants 2015, 4(2), 298-319; https://doi.org/10.3390/plants4020298 - 11 Jun 2015
Cited by 12 | Viewed by 4330
Abstract
Phytic acid (PA) biosynthesis pathway genes were reported from multiple crop species. PA accumulation was enhanced during grain filling and at that time, hormones like Abscisic acid (ABA) and Gibberellic acid (GA3) interplay to control the process of seed development. Regulation [...] Read more.
Phytic acid (PA) biosynthesis pathway genes were reported from multiple crop species. PA accumulation was enhanced during grain filling and at that time, hormones like Abscisic acid (ABA) and Gibberellic acid (GA3) interplay to control the process of seed development. Regulation of wheat PA pathway genes has not yet been reported in seeds. In an attempt to find the clues for the regulation by hormones, the promoter region of wheat PA pathway genes was analyzed for the presence of cis-elements. Multiple cis-elements of those known to be involved for ABA, GA3, salicylic acid (SA), and cAMP sensing were identified in the promoters of PA pathway genes. Eight genes (TaIMP, TaITPK1-4, TaPLC1, TaIPK2 and TaIPK1) involved in the wheat PA biosynthesis pathway were selected for the expression studies. The temporal expression response was studied in seeds treated with ABA and GA3 using quantitative real time PCR. Our results suggested that exogenous application of ABA induces few PA pathway genes in wheat grains. Comparison of expression profiles for PA pathway for GA3 and ABA suggested the antagonistic regulation of certain genes. Additionally, to reveal stress responses of wheat PA pathway genes, expression was also studied in the presence of SA and cAMP. Results suggested SA specific differential expression of few genes, whereas, overall repression of genes was observed in cAMP treated samples. This study is an effort to understand the regulation of PA biosynthesis genes in wheat. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Article
Certain Malvaceae Plants Have a Unique Accumulation of myo-Inositol 1,2,4,5,6-Pentakisphosphate
Plants 2015, 4(2), 267-283; https://doi.org/10.3390/plants4020267 - 29 May 2015
Cited by 3 | Viewed by 2897
Abstract
Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP6) and inositol pentakisphosphate (InsP [...] Read more.
Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP6) and inositol pentakisphosphate (InsP5) levels in leaves of different plants, a method was developed to concentrate and pre-purify these compounds prior to analysis. Inositol phosphates were extracted from leaves with diluted HCl and concentrated on small anion exchange columns. Reversed-phase solid phase extraction cartridges were used to remove compounds that give peaks that sometimes interfere during HPLC. The method permitted the determination of InsP6 and InsP5 concentrations in leaves as low as 10 µM and 2 µM, respectively. Most plants analyzed contained a high ratio of InsP6 to InsP5. In contrast, certain members of the Malvaceae family, such as cotton (Gossypium) and some hibiscus (Hibiscus) species, had a preponderance of InsP5. Radiolabeling of cotton seedlings also showed increased amounts of InsP5 relative to InsP6. Why some Malvaceae species exhibit a reversal of the typical ratios of these inositol phosphates is an intriguing question for future research. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Article
A Substantial Fraction of Barley (Hordeum vulgare L.) Low Phytic Acid Mutations Have Little or No Effect on Yield across Diverse Production Environments
Plants 2015, 4(2), 225-239; https://doi.org/10.3390/plants4020225 - 29 Apr 2015
Cited by 18 | Viewed by 3238
Abstract
The potential benefits of the low phytic acid (lpa) seed trait for human and animal nutrition, and for phosphorus management in non-ruminant animal production, are well documented. However, in many cases the lpa trait is associated with impaired seed or plant [...] Read more.
The potential benefits of the low phytic acid (lpa) seed trait for human and animal nutrition, and for phosphorus management in non-ruminant animal production, are well documented. However, in many cases the lpa trait is associated with impaired seed or plant performance, resulting in reduced yield. This has given rise to the perception that the lpa trait is tightly correlated with reduced yield in diverse crop species. Here we report a powerful test of this correlation. We measured grain yield in lines homozygous for each of six barley (Hordeum vulgare L.) lpa mutations that greatly differ in their seed phytic acid levels. Performance comparisons were between sibling wild-type and mutant lines obtained following backcrossing, and across two years in five Idaho (USA) locations that greatly differ in crop yield potential. We found that one lpa mutation (Hvlpa1-1) had no detectable effect on yield and a second (Hvlpa4-1) resulted in yield losses of only 3.5%, across all locations. When comparing yields in three relatively non-stressful production environments, at least three lpa mutations (Hvlpa1-1, Hvlpa3-1, and Hvlpa4-1) typically had yields similar to or within 5% of the wild-type sibling isoline. Therefore in the case of barley, lpa mutations can be readily identified that when simply incorporated into a cultivar result in adequately performing lines, even with no additional breeding for performance within the lpa line. In conclusion, while some barley lpa mutations do impact field performance, a substantial fraction appears to have little or no effect on yield. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Article
Overexpression of a Gene Involved in Phytic Acid Biosynthesis Substantially Increases Phytic Acid and Total Phosphorus in Rice Seeds
Plants 2015, 4(2), 196-208; https://doi.org/10.3390/plants4020196 - 24 Apr 2015
Cited by 10 | Viewed by 3380
Abstract
The manipulation of seed phosphorus is important for seedling growth and environmental P sustainability in agriculture. The mechanism of regulating P content in seed, however, is poorly understood. To study regulation of total P, we focused on phytic acid (inositol hexakisphosphate; InsP6 [...] Read more.
The manipulation of seed phosphorus is important for seedling growth and environmental P sustainability in agriculture. The mechanism of regulating P content in seed, however, is poorly understood. To study regulation of total P, we focused on phytic acid (inositol hexakisphosphate; InsP6) biosynthesis-related genes, as InsP6 is a major storage form of P in seeds. The rice (Oryza sativa L.) low phytic acid mutant lpa1-1 has been identified as a homolog of archael 2-phosphoglycerate kinase. The homolog might act as an inositol monophosphate kinase, which catalyzes a key step in InsP6 biosynthesis. Overexpression of the homolog in transgenic rice resulted in a significant increase in total P content in seed, due to increases in InsP6 and inorganic phosphates. On the other hand, overexpression of genes that catalyze the first and last steps of InsP6 biosynthesis could not increase total P levels. From the experiments using developing seeds, it is suggested that the activation of InsP6 biosynthesis in both very early and very late periods of seed development increases the influx of P from vegetative organs into seeds. This is the first report from a study attempting to elevate the P levels of seed through a transgenic approach. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Article
Accumulation of Phosphorus-Containing Compounds in Developing Seeds of Low-Phytate Pea (Pisum sativum L.) Mutants
Plants 2015, 4(1), 1-26; https://doi.org/10.3390/plants4010001 - 26 Dec 2014
Cited by 15 | Viewed by 4196
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Review

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Review
Seed Biofortification and Phytic Acid Reduction: A Conflict of Interest for the Plant?
Plants 2015, 4(4), 728-755; https://doi.org/10.3390/plants4040728 - 20 Nov 2015
Cited by 50 | Viewed by 4507
Abstract
Most of the phosphorus in seeds is accumulated in the form of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6). This molecule is a strong chelator of cations important for nutrition, such as iron, zinc, magnesium, and calcium. For this reason, [...] Read more.
Most of the phosphorus in seeds is accumulated in the form of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6). This molecule is a strong chelator of cations important for nutrition, such as iron, zinc, magnesium, and calcium. For this reason, InsP6 is considered an antinutritional factor. In recent years, efforts to biofortify seeds through the generation of low phytic acid (lpa) mutants have been noteworthy. Moreover, genes involved in the biosynthesis and accumulation of this molecule have been isolated and characterized in different species. Beyond its role in phosphorus storage, phytic acid is a very important signaling molecule involved in different regulatory processes during plant development and responses to different stimuli. Consequently, many lpa mutants show different negative pleitotropic effects. The strength of these pleiotropic effects depends on the specific mutated gene, possible functional redundancy, the nature of the mutation, and the spatio-temporal expression of the gene. Breeding programs or transgenic approaches aimed at development of new lpa mutants must take into consideration these different aspects in order to maximize the utility of these mutants. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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Review
Phytate (Inositol Hexakisphosphate) in Soil and Phosphate Acquisition from Inositol Phosphates by Higher Plants. A Review
Plants 2015, 4(2), 253-266; https://doi.org/10.3390/plants4020253 - 22 May 2015
Cited by 46 | Viewed by 4076
Abstract
Phosphate (P) fixation to the soil solid phase is considered to be important for P availability and is often attributed to the strong binding of orthophosphate anion species. However, the fixation and subsequent immobilization of inositolhexa and pentaphosphate isomers (phytate) in soil is [...] Read more.
Phosphate (P) fixation to the soil solid phase is considered to be important for P availability and is often attributed to the strong binding of orthophosphate anion species. However, the fixation and subsequent immobilization of inositolhexa and pentaphosphate isomers (phytate) in soil is often much stronger than that of the orthosphate anion species. The result is that phytate is a main organic P form in soil and the dominating form of identifiable organic P. The reasons for the accumulation are not fully clear. Two hypothesis can be found in the literature in the last 20 years, the low activity of phytase (phosphatases) in soil, which makes phytate P unavailable to the plant roots, and, on the other hand, the strong binding of phytate to the soil solid phase with its consequent stabilization and accumulation in soil. The hypothesis that low phytase activity is responsible for phytate accumulation led to the development of genetically modified plant genotypes with a higher expression of phytase activity at the root surface and research on the effect of a higher phytate activity on P acquisition. Obviously, this hypothesis has a basic assumption, that the phytate mobility in soil is not the limiting step for P acquisition of higher plants from soil phytate. This assumption is, however, not justified considering the results on the sorption, immobilization and fixation of phytate to the soil solid phase reported in the last two decades. Phytate is strongly bound, and the P sorption maximum and probably the sorption strength of phytate P to the soil solid phase is much higher, compared to that of orthophosphate P. Mobilization of phytate seems to be a promising step to make it available to the plant roots. The excretion of organic acid anions, citrate and to a lesser extend oxalate, seems to be an important way to make phytate P available to the plants. Phytase activity at the root surface seems not be the limiting step in P acquisition from phytate. Phytate is not only bound to inorganic surfaces in soil but can also be bound, similar to orthophosphate, to humic surfaces via Fe or Al bridges. Humic-metal-phytate complexes may be transported in the soil solution to the roots where hydrolysis and uptake of the liberated P may occur. Research on this topic is strongly required. Full article
(This article belongs to the Special Issue Phytic Acid Pathway and Breeding in Plants)
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