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Xu LL, Cui MQ, Xu C, Zhang MJ, Li GX, Xu JM, Wu XD, Mao CZ, Ding WN, Benhamed M, Ding ZJ, Zheng SJ. A clade of receptor-like cytoplasmic kinases and 14-3-3 proteins coordinate inositol hexaphosphate accumulation. Nat Commun 2024; 15:5107. [PMID: 38877001 PMCID: PMC11178898 DOI: 10.1038/s41467-024-49102-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 05/22/2024] [Indexed: 06/16/2024] Open
Abstract
Inositol hexaphosphate (InsP6) is the major storage form of phosphorus in seeds. Reducing seed InsP6 content is a breeding objective in agriculture, as InsP6 negatively impacts animal nutrition and the environment. Nevertheless, how InsP6 accumulation is regulated remains largely unknown. Here, we identify a clade of receptor-like cytoplasmic kinases (RLCKs), named Inositol Polyphosphate-related Cytoplasmic Kinases 1-6 (IPCK1-IPCK6), deeply involved in InsP6 accumulation. The InsP6 concentration is dramatically reduced in seeds of ipck quadruple (T-4m/C-4m) and quintuple (C-5m) mutants, accompanied with the obviously increase of phosphate (Pi) concentration. The plasma membrane-localized IPCKs recruit IPK1 involved in InsP6 synthesis, and facilitate its binding and activity via phosphorylation of GRF 14-3-3 proteins. IPCKs also recruit IPK2s and PI-PLCs required for InsP4/InsP5 and InsP3 biosynthesis respectively, to form a potential IPCK-GRF-PLC-IPK2-IPK1 complex. Our findings therefore uncover a regulatory mechanism of InsP6 accumulation governed by IPCKs, shedding light on the mechanisms of InsP biosynthesis in eukaryotes.
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Affiliation(s)
- Li Lin Xu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, 5100642, Guangzhou, China
| | - Meng Qi Cui
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, 5100642, Guangzhou, China
| | - Chen Xu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, 5100642, Guangzhou, China
| | - Miao Jing Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
| | - Gui Xin Li
- College of Agronomy and Biotechnology, Zhejiang University, 310058, Hangzhou, China
| | - Ji Ming Xu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
| | - Xiao Dan Wu
- Analysis Center of Agrobiology and Environmental Sciences, Zhejiang University, 310058, Hangzhou, China
| | - Chuan Zao Mao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China
| | - Wo Na Ding
- Ningbo Key Laboratory of Agricultural Germplasm Resources Mining and Environmental Regulation, College of Science and Technology, Ningbo University, 315300, Ningbo, China
| | - Moussa Benhamed
- Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 10 91405, Orsay, France
| | - Zhong Jie Ding
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China.
| | - Shao Jian Zheng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310058, Hangzhou, China.
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, 5100642, Guangzhou, China.
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Zhou T, Xing Q, Sun J, Wang P, Zhu J, Liu Z. The mechanism of KpMIPS gene significantly improves resistance of Koelreuteria paniculata to heavy metal cadmium in soil. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167219. [PMID: 37734601 DOI: 10.1016/j.scitotenv.2023.167219] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 08/28/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
Cadmium (Cd) pollution in soil is an important factor endangering plant growth and harming human health through food chains. Koelreuteria paniculata is an important woody plant for ecological restoration of Cd-contaminated soils. In this study, KpMIPS gene of K. paniculata was cloned, and the expressed protein (60 kDa) had 1-phosphate synthase activity. The results showed that KpMIPS significantly promoted root development of K. paniculata and Arabidopsis thaliana, reduced damage to the roots of Arabidopsis thaliana caused by Cd, and decreased transfer of Cd to the aboveground parts of K. paniculata and Arabidopsis thaliana . In the K. paniculata plants overexpressing KpMIPS integrity of the root cells was maintained and the content of pectin and phytic acid was significantly increased. Overexpression of KpMIPS increased the Cd accumulation in the roots and decreased the Cd content in the stems and leaves. Clearly, KpMIPS could regulate the contents of pectin and phytic acid in K. paniculata, thereby passivating Cd2+ and enriching it in the root cell wall, reducing the transfer of free Cd2+ to other parts of K. paniculata, and providing a positive regulatory effect on the Cd resistance of K. paniculata. The results of the study provide a technical introduction for the selection and genetic improvement of target genes regulating heavy metal resistance of plants in phytoremediation technology.
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Affiliation(s)
- Tao Zhou
- College of Life Science and Technology, Central South University of Forestry and Technology, No. 498, South Shaoshan Road, Changsha 410004, Hunan Province, China
| | - Qinqin Xing
- College of Life Science and Technology, Central South University of Forestry and Technology, No. 498, South Shaoshan Road, Changsha 410004, Hunan Province, China
| | - Jikang Sun
- College of Life Science and Technology, Central South University of Forestry and Technology, No. 498, South Shaoshan Road, Changsha 410004, Hunan Province, China
| | - Ping Wang
- College of Environmental Science and Engineering, Central South University of Forestry and Technology, No. 498, South Shaoshan Road, Changsha 410004, Hunan Province, China.
| | - Jian Zhu
- College of Environmental Science and Engineering, Central South University of Forestry and Technology, No. 498, South Shaoshan Road, Changsha 410004, Hunan Province, China.
| | - Zhiming Liu
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, United States of America
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The inositol pyrophosphate metabolism of Dictyostelium discoideum does not regulate inorganic polyphosphate (polyP) synthesis. Adv Biol Regul 2021; 83:100835. [PMID: 34782304 PMCID: PMC8885430 DOI: 10.1016/j.jbior.2021.100835] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 11/23/2022]
Abstract
Initial studies on the inositol phosphates metabolism were enabled by the social amoeba Dictyostelium discoideum. The abundant amount of inositol hexakisphosphate (IP6 also known as Phytic acid) present in the amoeba allowed the discovery of the more polar inositol pyrophosphates, IP7 and IP8, possessing one or two high energy phosphoanhydride bonds, respectively. Considering the contemporary growing interest in inositol pyrophosphates, it is surprising that in recent years D. discoideum, has contributed little to our understanding of their metabolism and function. This work fulfils this lacuna, by analysing the ip6k, ppip5k and ip6k-ppip5K amoeba null strains using PAGE, 13C-NMR and CE-MS analysis. Our study reveals an inositol pyrophosphate metabolism more complex than previously thought. The amoeba Ip6k synthesizes the 4/6-IP7 in contrast to the 5-IP7 isomer synthesized by the mammalian homologue. The amoeba Ppip5k synthesizes the same 1/3-IP7 as the mammalian enzyme. In D. discoideum, the ip6k strain possesses residual amounts of IP7. The residual IP7 is also present in the ip6k-ppip5K strain, while the ppip5k single mutant shows a decrease in both IP7 and IP8 levels. This phenotype is in contrast to the increase in IP7 observable in the yeast vip1Δ strain. The presence of IP8 in ppip5k and the presence of IP7 in ip6k-ppip5K indicate the existence of an additional inositol pyrophosphate synthesizing enzyme. Additionally, we investigated the existence of a metabolic relationship between inositol pyrophosphate synthesis and inorganic polyphosphate (polyP) metabolism as observed in yeast. These studies reveal that contrary to the yeast, Ip6k and Ppip5k do not control polyP cellular level in amoeba.
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CRISPR/Cas9 mediated disruption of Inositol Pentakisphosphate 2-Kinase 1 (TaIPK1) reduces phytic acid and improves iron and zinc accumulation in wheat grains. J Adv Res 2021; 37:33-41. [PMID: 35499048 PMCID: PMC9039650 DOI: 10.1016/j.jare.2021.07.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/19/2021] [Accepted: 07/09/2021] [Indexed: 11/24/2022] Open
Abstract
This study, for the first time, used CRISPR/Cas9 to disrupt TaIPK1 gene in wheat. Disruption of TaIPK1 gene reduces phytic acid and enhanced Iron and Zinc in wheat grains. This study will help to develop the biofortified wheat and reducing the malnutrition. This study provided a great resource for the development of biofortified wheat using CRISPR/Cas9.
Introduction Phytic acid (PA) is an important antinutrient agent present in cereal grains which reduces the bioavailability of iron and zinc in human body, causing malnutrition. Inositol pentakisphosphate 2- kinase 1 (IPK1) gene has been reported to be an important gene for PA biosynthesis. Objective A recent genome editing tool CRISPR/Cas9 has been successfully applied to develop biofortified rice by disrupting IPK1 gene, however, it remained a challenge in wheat. The aim of this study was to biofortify wheat using CRISPR/Cas9. Methods In this study, we isolated 3 TaIPK1 homeologs in wheat designated as TaIPK1.A, TaIPK1.B and TaIPK1.D and found that the expression abundance of TaIPK1.A was stronger in early stages of grain filling. Using CRISPR/Cas9, we have disrupted TaIPK1.A gene in cv. Borlaug-2016 with two guide RNAs targeting the 1st and 2nd exons. Results We got several genome-edited lines in the T0 generation at frequencies of 12.7% and 10.8%. Sequencing analysis revealed deletion of 1–23 nucleotides and even an addition of 1 nucleotide in various lines. Analysis of the genome-edited lines revealed a significant decrease in the PA content and an increase in iron and zinc accumulation in grains compared with control plants. Conclusion Our study demonstrates the potential application of CRISPR/Cas9 technique for the rapid generation of biofortified wheat cultivars.
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Mantilla BS, Do Amaral LD, Jessen HJ, Docampo R. The Inositol Pyrophosphate Biosynthetic Pathway of Trypanosoma cruzi. ACS Chem Biol 2021; 16:283-292. [PMID: 33411501 PMCID: PMC10466500 DOI: 10.1021/acschembio.0c00759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Inositol phosphates (IPs) are phosphorylated derivatives of myo-inositol involved in the regulation of several cellular processes through their interaction with specific proteins. Their synthesis relies on the activity of specific kinases that use ATP as phosphate donor. Here, we combined reverse genetics and liquid chromatography coupled to mass spectrometry (LC-MS) to dissect the inositol phosphate biosynthetic pathway and its metabolic intermediates in the main life cycle stages (epimastigotes, cell-derived trypomastigotes, and amastigotes) of Trypanosoma cruzi, the etiologic agent of Chagas disease. We found evidence of the presence of highly phosphorylated IPs, like inositol hexakisphosphate (IP6), inositol heptakisphosphate (IP7), and inositol octakisphosphate (IP8), that were not detected before by HPLC analyses of the products of radiolabeled exogenous inositol. The kinases involved in their synthesis (inositol polyphosphate multikinase (TcIPMK), inositol 5-phosphate kinase (TcIP5K), and inositol 6-phosphate kinase (TcIP6K)) were also identified. TcIPMK is dispensable in epimastigotes, important for the synthesis of polyphosphate, and critical for the virulence of the infective stages. TcIP5K is essential for normal epimastigote growth, while TcIP6K mutants displayed defects in epimastigote motility and growth. Our results demonstrate the relevance of highly phosphorylated IPs in the life cycle of T. cruzi.
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Affiliation(s)
- Brian S. Mantilla
- Center for Tropical and Emerging Global Diseases, and Department of Cellular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Leticia D. Do Amaral
- Center for Tropical and Emerging Global Diseases, and Department of Cellular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Henning J. Jessen
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg, 79104 Freiburg, Germany
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases, and Department of Cellular Biology, University of Georgia, Athens, GA, 30602, USA
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Jiang M, Liu Y, Li R, Li S, Tan Y, Huang J, Shu Q. An Inositol 1, 3, 4, 5, 6-Pentakisphosphate 2-Kinase 1 Mutant with a 33-nt Deletion Showed Enhanced Tolerance to Salt and Drought Stress in Rice. PLANTS 2020; 10:plants10010023. [PMID: 33374298 PMCID: PMC7824669 DOI: 10.3390/plants10010023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 12/22/2020] [Accepted: 12/22/2020] [Indexed: 01/24/2023]
Abstract
OsIPK1 encodes inositol 1,3,4,5,6-pentakisphosphate 2-kinase, which catalyzes the conversion of myo-inositol-1,3,4,5,6-pentakisphosphate to myo-inositol-1,2,3,4,5,6-hexakisphosphate (IP6) in rice. By clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (Cas9)-mediated mutagenesis in the 3rd exon of the gene, three OsIPK1 mutations, i.e., osipk1_1 (a 33-nt deletion), osipk1_2 (a 1-nt deletion), and osipk1_3 (a 2-nt deletion) were identified in T0 plants of the rice line Xidao #1 (wild type, WT). A transfer DNA free line with the homozygous osipk1_1 mutation was developed; however, no homozygous mutant lines could be developed for the other two mutations. The comparative assay showed that the osipk1_1 mutant line had a significantly lower level of phytic acid (PA, IP6; −19.5%) in rice grain and agronomic traits comparable to the WT. However, the osipk1_1 mutant was more tolerant to salt and drought stresses than the WT, with significantly lower levels of inositol triphosphate (IP3), reactive oxygen species (ROS) and induced IP6, and higher activities of antioxidant enzymes in seedlings subjected to these stresses. Further analyses showed that the transcription of stress response genes was significantly upregulated in the osipk1_1 mutant under stress. Thus, the low phytic acid mutant osipk1_1 should have potential applications in rice breeding and production.
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Affiliation(s)
- Meng Jiang
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
- Hainan Institute of Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya 572000, China
| | - Yanhua Liu
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
| | - Ruiqing Li
- College of Agronomy, Anhui Agricultural University, Hefei 230036, China;
| | - Shan Li
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
| | - Yuanyuan Tan
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
| | - Jianzhong Huang
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
- Institute of Nuclear Agricultural Sciences, Zhejiang University, Hangzhou 310058, China
| | - Qingyao Shu
- National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou 310058, China; (M.J.); (Y.L.); (S.L.); (Y.T.); (J.H.)
- Hainan Institute of Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya 572000, China
- Correspondence:
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Freed C, Adepoju O, Gillaspy G. Can Inositol Pyrophosphates Inform Strategies for Developing Low Phytate Crops? PLANTS (BASEL, SWITZERLAND) 2020; 9:E115. [PMID: 31963418 PMCID: PMC7020182 DOI: 10.3390/plants9010115] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/14/2020] [Accepted: 01/15/2020] [Indexed: 01/01/2023]
Abstract
Inositol pyrophosphates (PP-InsPs) are an emerging class of "high-energy" intracellular signaling molecules, containing one or two diphosphate groups attached to an inositol ring, that are connected with phosphate sensing, jasmonate signaling, and inositol hexakisphosphate (InsP6) storage in plants. While information regarding this new class of signaling molecules in plants is scarce, the enzymes responsible for their synthesis have recently been elucidated. This review focuses on InsP6 synthesis and its conversion into PP-InsPs, containing seven and eight phosphate groups (InsP7 and InsP8). These steps involve two types of enzymes: the ITPKs that phosphorylate InsP6 to InsP7, and the PPIP5Ks that phosphorylate InsP7 to InsP8. This review also considers the potential roles of PP-InsPs in plant hormone and inorganic phosphate (Pi) signaling, along with an emerging role in bioenergetic homeostasis. PP-InsP synthesis and signaling are important for plant breeders to consider when developing strategies that reduce InsP6 in plants, as this will likely also reduce PP-InsPs. Thus, this review is primarily intended to bridge the gap between the basic science aspects of PP-InsP synthesis/signaling and breeding/engineering strategies to fortify foods by reducing InsP6.
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Affiliation(s)
| | | | - Glenda Gillaspy
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA (O.A.)
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Metabolic Labeling of Inositol Phosphates and Phosphatidylinositols in Yeast and Mammalian Cells. Methods Mol Biol 2020; 2091:83-92. [PMID: 31773572 DOI: 10.1007/978-1-0716-0167-9_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Inositol phosphate (IP) and phosphatidylinositol (PI) signaling are critical signal transduction pathways responsible for generating numerous receptor-mediated cellular responses. Biochemical and genetic studies have revealed diverse roles of IP and PI signaling in eukaryotic signaling, but detailed characterization of unique IP and PI signaling profiles in response to different agonists and among cell types remains largely unexplored. Here, we outline steady-state inositol metabolic-labeling techniques that can be leveraged to assess the IP and PI signaling state in eukaryotic cells. This flexible technique can be amended and optimized to your cell line of interest, perturbed with biochemical, genetic, or pharmacological alteration, and used to provide comprehensive inositol profiling in various cellular systems.
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Abstract
The multitudinous inositol phosphate family elicits a wide range of molecular effects that regulate countless biological responses. In this review, I provide a methodological viewpoint of the manner in which key advances in the field of inositol phosphate research were made. I also note some of the considerable challenges that still lie ahead.
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Affiliation(s)
- Stephen B Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
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Dictyostelium discoideum as a Model to Study Inositol Polyphosphates and Inorganic Polyphosphate. Methods Mol Biol 2019. [PMID: 31773570 DOI: 10.1007/978-1-0716-0167-9_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The yeast Saccharomyces cerevisiae has given us much information on the metabolism and function of inositol polyphosphates and inorganic polyphosphate. To expand our knowledge of the metabolic as well as functional connections between inositol polyphosphates and inorganic polyphosphate, we have refined and developed techniques to extract and analyze these molecules in a second eukaryotic experimental model, the amoeba Dictyostelium discoideum. This amoeba, possessing a well-defined developmental program, is ideal to study physiological changes in the levels of inositol polyphosphates and inorganic polyphosphate, since levels of both molecules increase at late stages of development. We detail here the methods used to extract inositol polyphosphates using perchloric acid and inorganic polyphosphate using acidic phenol. We also present the postextraction procedures to visualize and quantify these molecules by polyacrylamide gel electrophoresis and by malachite green assay.
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ITPK1 mediates the lipid-independent synthesis of inositol phosphates controlled by metabolism. Proc Natl Acad Sci U S A 2019; 116:24551-24561. [PMID: 31754032 PMCID: PMC6900528 DOI: 10.1073/pnas.1911431116] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Inositol phosphates (IPs) are a class of signaling molecules regulating cell physiology. The best-characterized IP, the calcium release factor IP3, is generated by phospholipase C hydrolysis of phosphoinositides lipids. For historical and technical reasons, IPs synthesis is believed to originate from the lipid-generated IP3. While this is true in yeast, our work has demonstrated that other organisms use a “soluble” (nonlipid) route to synthesize IPs. This soluble pathway depends on the metabolic status of the cells, and is under the control of the kinase ITPK1, which phosphorylates inositol monophosphate likely generated from glucose. The data shed light on the evolutionary origin of IPs, signaling and tightening the link between these small molecules and basic metabolism. Inositol phosphates (IPs) comprise a network of phosphorylated molecules that play multiple signaling roles in eukaryotes. IPs synthesis is believed to originate with IP3 generated from PIP2 by phospholipase C (PLC). Here, we report that in mammalian cells PLC-generated IPs are rapidly recycled to inositol, and uncover the enzymology behind an alternative “soluble” route to synthesis of IPs. Inositol tetrakisphosphate 1-kinase 1 (ITPK1)—found in Asgard archaea, social amoeba, plants, and animals—phosphorylates I(3)P1 originating from glucose-6-phosphate, and I(1)P1 generated from sphingolipids, to enable synthesis of IP6. We also found using PAGE mass assay that metabolic blockage by phosphate starvation surprisingly increased IP6 levels in a ITPK1-dependent manner, establishing a route to IP6 controlled by cellular metabolic status, that is not detectable by traditional [3H]-inositol labeling. The presence of ITPK1 in archaeal clades thought to define eukaryogenesis indicates that IPs had functional roles before the appearance of the eukaryote.
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Whitfield H, Riley AM, Diogenous S, Godage HY, Potter BVL, Brearley CA. Simple synthesis of 32P-labelled inositol hexakisphosphates for study of phosphate transformations. PLANT AND SOIL 2018; 427:149-161. [PMID: 29880988 PMCID: PMC5984642 DOI: 10.1007/s11104-017-3315-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 06/12/2017] [Indexed: 06/08/2023]
Abstract
BACKGROUND AND AIMS In many soils inositol hexakisphosphate in its various forms is as abundant as inorganic phosphate. The organismal and geochemical processes that exchange phosphate between inositol hexakisphosphate and other pools of soil phosphate are poorly defined, as are the organisms and enzymes involved. We rationalized that simple enzymic synthesis of inositol hexakisphosphate labeled with 32P would greatly enable study of transformation of soil inositol phosphates when combined with robust HPLC separations of different inositol phosphates. METHODS We employed the enzyme inositol pentakisphosphate 2-kinase, IP5 2-K, to transfer phosphate from [γ-32P]ATP to axial hydroxyl(s) of myo-, neo- and 1D-chiro-inositol phosphate substrates. RESULTS 32P-labeled inositol phosphates were separated by anion exchange HPLC with phosphate eluents. Additional HPLC methods were developed to allow facile separation of myo-, neo-, 1D-chiro- and scyllo-inositol hexakisphosphate on acid gradients. CONCLUSIONS We developed enzymic approaches that allow the synthesis of labeled myo-inositol 1,[32P]2,3,4,5,6-hexakisphosphate; neo-inositol 1,[32P]2,3,4,[32P]5,6 - hexakisphosphate and 1D-chiro-inositol [32P]1,2,3,4,5,[32P]6-hexakisphosphate. Additionally, we describe HPLC separations of all inositol hexakisphosphates yet identified in soils, using a collection of soil inositol phosphates described in the seminal historic studies of Cosgrove, Tate and coworkers. Our study will enable others to perform radiotracer experiments to analyze fluxes of phosphate to/from inositol hexakisphosphates in different soils.
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Affiliation(s)
- Hayley Whitfield
- School of Biological Sciences, University of Norwich, Norwich Research Park, Norwich, NR4 7TJ UK
| | - Andrew M. Riley
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford, OX1 3QT UK
| | - Soulla Diogenous
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Himali Y. Godage
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Barry V. L. Potter
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford, OX1 3QT UK
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Charles A. Brearley
- School of Biological Sciences, University of Norwich, Norwich Research Park, Norwich, NR4 7TJ UK
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Kuo HF, Hsu YY, Lin WC, Chen KY, Munnik T, Brearley CA, Chiou TJ. Arabidopsis inositol phosphate kinases IPK1 and ITPK1 constitute a metabolic pathway in maintaining phosphate homeostasis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018. [PMID: 29779236 DOI: 10.1101/270355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/02/2018] [Accepted: 05/09/2018] [Indexed: 05/27/2023]
Abstract
Emerging studies have suggested that there is a close link between inositol phosphate (InsP) metabolism and cellular phosphate (Pi ) homeostasis in eukaryotes; however, whether a common InsP species is deployed as an evolutionarily conserved metabolic messenger to mediate Pi signaling remains unknown. Here, using genetics and InsP profiling combined with Pi -starvation response (PSR) analysis in Arabidopsis thaliana, we showed that the kinase activity of inositol pentakisphosphate 2-kinase (IPK1), an enzyme required for phytate (inositol hexakisphosphate; InsP6 ) synthesis, is indispensable for maintaining Pi homeostasis under Pi -replete conditions, and inositol 1,3,4-trisphosphate 5/6-kinase 1 (ITPK1) plays an equivalent role. Although both ipk1-1 and itpk1 mutants exhibited decreased levels of InsP6 and diphosphoinositol pentakisphosphate (PP-InsP5 ; InsP7 ), disruption of another ITPK family enzyme, ITPK4, which correspondingly caused depletion of InsP6 and InsP7 , did not display similar Pi -related phenotypes, which precludes these InsP species from being effectors. Notably, the level of d/l-Ins(3,4,5,6)P4 was concurrently elevated in both ipk1-1 and itpk1 mutants, which showed a specific correlation with the misregulated Pi phenotypes. However, the level of d/l-Ins(3,4,5,6)P4 is not responsive to Pi starvation that instead manifests a shoot-specific increase in the InsP7 level. This study demonstrates a more nuanced picture of the intersection of InsP metabolism and Pi homeostasis and PSRs than has previously been elaborated, and additionally establishes intermediate steps to phytate biosynthesis in plant vegetative tissues.
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Affiliation(s)
- Hui-Fen Kuo
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Yu-Ying Hsu
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Wei-Chi Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Kai-Yu Chen
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Teun Munnik
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, Amsterdam, 1098XH, The Netherlands
| | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Tzyy-Jen Chiou
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
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14
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Kuo HF, Hsu YY, Lin WC, Chen KY, Munnik T, Brearley CA, Chiou TJ. Arabidopsis inositol phosphate kinases IPK1 and ITPK1 constitute a metabolic pathway in maintaining phosphate homeostasis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 95:613-630. [PMID: 29779236 DOI: 10.1111/tpj.13974] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/02/2018] [Accepted: 05/09/2018] [Indexed: 05/21/2023]
Abstract
Emerging studies have suggested that there is a close link between inositol phosphate (InsP) metabolism and cellular phosphate (Pi ) homeostasis in eukaryotes; however, whether a common InsP species is deployed as an evolutionarily conserved metabolic messenger to mediate Pi signaling remains unknown. Here, using genetics and InsP profiling combined with Pi -starvation response (PSR) analysis in Arabidopsis thaliana, we showed that the kinase activity of inositol pentakisphosphate 2-kinase (IPK1), an enzyme required for phytate (inositol hexakisphosphate; InsP6 ) synthesis, is indispensable for maintaining Pi homeostasis under Pi -replete conditions, and inositol 1,3,4-trisphosphate 5/6-kinase 1 (ITPK1) plays an equivalent role. Although both ipk1-1 and itpk1 mutants exhibited decreased levels of InsP6 and diphosphoinositol pentakisphosphate (PP-InsP5 ; InsP7 ), disruption of another ITPK family enzyme, ITPK4, which correspondingly caused depletion of InsP6 and InsP7 , did not display similar Pi -related phenotypes, which precludes these InsP species from being effectors. Notably, the level of d/l-Ins(3,4,5,6)P4 was concurrently elevated in both ipk1-1 and itpk1 mutants, which showed a specific correlation with the misregulated Pi phenotypes. However, the level of d/l-Ins(3,4,5,6)P4 is not responsive to Pi starvation that instead manifests a shoot-specific increase in the InsP7 level. This study demonstrates a more nuanced picture of the intersection of InsP metabolism and Pi homeostasis and PSRs than has previously been elaborated, and additionally establishes intermediate steps to phytate biosynthesis in plant vegetative tissues.
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Affiliation(s)
- Hui-Fen Kuo
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Yu-Ying Hsu
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Wei-Chi Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Kai-Yu Chen
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Teun Munnik
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, Amsterdam, 1098XH, The Netherlands
| | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Tzyy-Jen Chiou
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan
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15
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Al-Anbaky Q, Al-Karakooly Z, Connor R, Williams L, Yarbrough A, Bush J, Ali N. Role of inositol polyphosphates in programed cell death in Dictyostelium discoideum and its developmental life cycle. Mol Cell Biochem 2018; 449:237-250. [PMID: 29679279 DOI: 10.1007/s11010-018-3360-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 04/16/2018] [Indexed: 11/28/2022]
Abstract
Programed cell death or apoptosis is a key developmental process that maintains tissue homeostasis in multicellular organisms. Inositol polyphosphates (InsPs) are key signaling molecules known to regulate a variety of cellular processes including apoptosis in such organisms. The signaling role of InsPs in unicellular organisms such as Dictyostelium discoideum (D. discoideum) is not well understood. We investigated whether InsPs also play any role in apoptosis in D. discoideum and whether InsPs-mediated apoptosis follows a mechanism similar to that present in higher multicellular eukaryotes. We measured known apoptotic markers in response to exogenously administered InsP6, the major InsPs in the cell. We found that InsP6 was able to cause cell death in D. discoideum cell culture in a dose- and time-dependent manner as determined by cytotoxicity assays. Fluorescence staining with acridine orange/ethidium bromide and flow cytometry results confirmed that the cell death in D. discoideum by InsP6 was due to apoptotic changes. Poly(ADP-ribose) expression, a known apoptotic marker used in D. discoideum, was also increased following InsP6 treatment suggesting a role for InsP6-mediated apoptosis in this organism. InsP6-mediated cell death was accompanied by production of reactive oxygen species and a decrease in mitochondrial membrane potential. Additionally, we studied the effects of InsP6 on the developmental life cycle of D. discoideum, the process likely affected by apoptosis. In conclusion, our studies provide evidence that InsP6-mediated cell death process is conserved in D. discoideum and plays an important signaling role in its developmental life cycle.
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Affiliation(s)
- Qudes Al-Anbaky
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA.,Department of Biology, University of Diyala, Baquba, Iraq
| | - Zeiyad Al-Karakooly
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Richard Connor
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Lisa Williams
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Azure Yarbrough
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - John Bush
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA
| | - Nawab Ali
- Department of Biology, College of Arts, Letters and Sciences, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR, 72204, USA.
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16
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Doolette AL, Smernik RJ. Facile decomposition of phytate in the solid-state: Kinetics and decomposition pathways. PHOSPHORUS SULFUR 2017. [DOI: 10.1080/10426507.2017.1416614] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Ashlea L. Doolette
- School of Agriculture, Food and Wine and Waite Research Institute, The University of Adelaide, Glen Osmond, SA, Australia
| | - Ronald J. Smernik
- School of Agriculture, Food and Wine and Waite Research Institute, The University of Adelaide, Glen Osmond, SA, Australia
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17
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Saiardi A, Azevedo C, Desfougères Y, Portela-Torres P, Wilson MSC. Microbial inositol polyphosphate metabolic pathway as drug development target. Adv Biol Regul 2017; 67:74-83. [PMID: 28964726 DOI: 10.1016/j.jbior.2017.09.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 09/20/2017] [Accepted: 09/21/2017] [Indexed: 12/27/2022]
Abstract
Inositol polyphosphates are a diverse and multifaceted class of intracellular messengers omnipresent in eukaryotic cells. These water-soluble molecules regulate many aspects of fundamental cell physiology. Removing this metabolic pathway is deleterious: inositol phosphate kinase null mutations can result in lethality or substantial growth phenotypes. Inositol polyphosphate synthesis occurs through the actions of a set of kinases that phosphorylate phospholipase-generated IP3 to higher phosphorylated forms, such as the fully phosphorylated IP6 and the inositol pyrophosphates IP7 and IP8. Unicellular organisms have a reduced array of the kinases for synthesis of higher phosphorylated inositol polyphosphates, while human cells possess two metabolic routes to IP6. The enzymes responsible for inositol polyphosphate synthesis have been identified in all eukaryote genomes, although their amino acid sequence homology is often barely detectable by common search algorithms. Homology between human and microbial inositol phosphate kinases is restricted to a few catalytically important residues. Recent studies of the inositol phosphate metabolic pathways in pathogenic fungi (Cryptococcus neoformans) and protozoa (Trypanosome brucei) have revealed the importance of the highly phosphorylated inositol polyphosphates to the fitness and thus virulence of these pathogens. Given this, identification of inositol kinase inhibitors specifically targeting the kinases of pathogenic microorganisms is desirable and achievable.
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Affiliation(s)
- Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK.
| | - Cristina Azevedo
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Yann Desfougères
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Paloma Portela-Torres
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Miranda S C Wilson
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
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18
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Wilson MSC, Saiardi A. Importance of Radioactive Labelling to Elucidate Inositol Polyphosphate Signalling. Top Curr Chem (Cham) 2017; 375:14. [PMID: 28101851 PMCID: PMC5396384 DOI: 10.1007/s41061-016-0099-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/21/2016] [Indexed: 01/09/2023]
Abstract
Inositol polyphosphates, in their water-soluble or lipid-bound forms, represent a large and multifaceted family of signalling molecules. Some inositol polyphosphates are well recognised as defining important signal transduction pathways, as in the case of the calcium release factor Ins(1,4,5)P3, generated by receptor activation-induced hydrolysis of the lipid PtdIns(4,5)P2 by phospholipase C. The birth of inositol polyphosphate research would not have occurred without the use of radioactive phosphate tracers that enabled the discovery of the “PI response”. Radioactive labels, mainly of phosphorus but also carbon and hydrogen (tritium), have been instrumental in the development of this research field and the establishment of the inositol polyphosphates as one of the most important networks of regulatory molecules present in eukaryotic cells. Advancements in microscopy and mass spectrometry and the development of colorimetric assays have facilitated inositol polyphosphate research, but have not eliminated the need for radioactive experimental approaches. In fact, such experiments have become easier with the cloning of the inositol polyphosphate kinases, enabling the systematic labelling of specific positions of the inositol ring with radioactive phosphate. This approach has been valuable for elucidating their metabolic pathways and identifying specific and novel functions for inositol polyphosphates. For example, the synthesis of radiolabelled inositol pyrophosphates has allowed the discovery of a new protein post-translational modification. Therefore, radioactive tracers have played and will continue to play an important role in dissecting the many complex aspects of inositol polyphosphate physiology. In this review we aim to highlight the historical importance of radioactivity in inositol polyphosphate research, as well as its modern usage.
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Affiliation(s)
- Miranda S C Wilson
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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19
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Abstract
Between spring 1982 and autumn 1984 the physiological role of Ins(1,4,5)P3 as a calcium-mobilizing second messenger was first suggested and then experimentally established. At the same time the unexpected complexity of inositide metabolism began to be exposed by the discovery of Ins(1,3,4)P3. This article recalls my entanglement with these two inositol phosphates.
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20
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Wilson MSC, Bulley SJ, Pisani F, Irvine RF, Saiardi A. A novel method for the purification of inositol phosphates from biological samples reveals that no phytate is present in human plasma or urine. Open Biol 2015; 5:150014. [PMID: 25808508 PMCID: PMC4389793 DOI: 10.1098/rsob.150014] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Inositol phosphates are a large and diverse family of signalling molecules. While
genetic studies have discovered important functions for them, the biochemistry
behind these roles is often not fully characterized. A key obstacle in inositol
phosphate research in mammalian cells has been the lack of straightforward
techniques for their purification and analysis. Here we describe the ability of
titanium dioxide (TiO2) beads to bind inositol phosphates. This
discovery allowed the development of a new purification protocol that, coupled
with gel analysis, permitted easy identification and quantification of
InsP6 (phytate), its pyrophosphate derivatives InsP7
and InsP8, and the nucleotides ATP and GTP from cell or tissue
extracts. Using this approach, InsP6, InsP7 and
InsP8 were visualized in Dictyostelium extracts
and a variety of mammalian cell lines and tissues, and the effects of metabolic
perturbation on these were explored. TiO2 bead purification also
enabled us to quantify InsP6 in human plasma and urine, which led to
two distinct but related observations. Firstly, there is an active
InsP6 phosphatase in human plasma, and secondly, InsP6
is undetectable in either fluid. These observations seriously question reports
that InsP6 is present in human biofluids and the advisability of
using InsP6 as a dietary supplement.
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Affiliation(s)
- Miranda S C Wilson
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Simon J Bulley
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK Department of Haematology, Cambridge University Hospitals NHS Trust, Hills Road, Cambridge CB2 0QQ, UK
| | - Francesca Pisani
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Robin F Irvine
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
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21
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Ca2+ Regulation of Trypanosoma brucei Phosphoinositide Phospholipase C. EUKARYOTIC CELL 2015; 14:486-94. [PMID: 25769297 DOI: 10.1128/ec.00019-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 03/09/2015] [Indexed: 11/20/2022]
Abstract
We characterized a phosphoinositide phospholipase C (PI-PLC) from the procyclic form (PCF) of Trypanosoma brucei. The protein contains a domain organization characteristic of typical PI-PLCs, such as X and Y catalytic domains, an EF-hand calcium-binding motif, and a C2 domain, but it lacks a pleckstrin homology (PH) domain. In addition, the T. brucei PI-PLC (TbPI-PLC) contains an N-terminal myristoylation consensus sequence found only in trypanosomatid PI-PLCs. A peptide containing this N-terminal domain fused to green fluorescent protein (GFP) was targeted to the plasma membrane. TbPI-PLC enzymatic activity was stimulated by Ca(2+) concentrations below the cytosolic levels in the parasite, suggesting that the enzyme is constitutively active. TbPI-PLC hydrolyzes both phosphatidylinositol (PI) and phosphatidylinositol 4,5-bisphosphate (PIP2), with a higher affinity for PIP2. We found that modification of a single amino acid in the EF-hand motif greatly affected the protein's Ca(2+) sensitivity and substrate preference, demonstrating the role of this motif in Ca(2+) regulation of TbPI-PLC. Endogenous TbPI-PLC localizes to intracellular vesicles and might be using an intracellular source of PIP2. Knockdown of TbPI-PLC expression by RNA interference (RNAi) did not result in growth inhibition, although enzymatic activity was still present in parasites, resulting in hydrolysis of PIP2 and a contribution to the inositol 1,4,5-trisphosphate (IP3)/diacylglycerol (DAG) pathway.
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22
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Weber S, Stirnimann CU, Wieser M, Frey D, Meier R, Engelhardt S, Li X, Capitani G, Kammerer RA, Hilbi H. A type IV translocated Legionella cysteine phytase counteracts intracellular growth restriction by phytate. J Biol Chem 2014; 289:34175-88. [PMID: 25339170 DOI: 10.1074/jbc.m114.592568] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The causative agent of Legionnaires' pneumonia, Legionella pneumophila, colonizes diverse environmental niches, including biofilms, plant material, and protozoa. In these habitats, myo-inositol hexakisphosphate (phytate) is prevalent and used as a phosphate storage compound or as a siderophore. L. pneumophila replicates in protozoa and mammalian phagocytes within a unique "Legionella-containing vacuole." The bacteria govern host cell interactions through the Icm/Dot type IV secretion system (T4SS) and ∼300 different "effector" proteins. Here we characterize a hitherto unrecognized Icm/Dot substrate, LppA, as a phytate phosphatase (phytase). Phytase activity of recombinant LppA required catalytically essential cysteine (Cys(231)) and arginine (Arg(237)) residues. The structure of LppA at 1.4 Å resolution revealed a mainly α-helical globular protein stabilized by four antiparallel β-sheets that binds two phosphate moieties. The phosphates localize to a P-loop active site characteristic of dual specificity phosphatases or to a non-catalytic site, respectively. Phytate reversibly abolished growth of L. pneumophila in broth, and growth inhibition was relieved by overproduction of LppA or by metal ion titration. L. pneumophila lacking lppA replicated less efficiently in phytate-loaded Acanthamoeba castellanii or Dictyostelium discoideum, and the intracellular growth defect was complemented by the phytase gene. These findings identify the chelator phytate as an intracellular bacteriostatic component of cell-autonomous host immunity and reveal a T4SS-translocated L. pneumophila phytase that counteracts intracellular bacterial growth restriction by phytate. Thus, bacterial phytases might represent therapeutic targets to combat intracellular pathogens.
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Affiliation(s)
- Stephen Weber
- From the Max von Pettenkofer Institute, Department of Medicine, Ludwig-Maximilians University Munich, 80336 Munich, Germany
| | - Christian U Stirnimann
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Mara Wieser
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Daniel Frey
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Roger Meier
- the Scientific Center for Optical and Electron Microscopy, ETH Zurich, 8093 Zurich, Switzerland
| | - Sabrina Engelhardt
- the Institute of Veterinary Physiology and Zurich Center for Integrative Human Physiology (ZIHP), Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland, and
| | - Xiaodan Li
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Guido Capitani
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Richard A Kammerer
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Hubert Hilbi
- From the Max von Pettenkofer Institute, Department of Medicine, Ludwig-Maximilians University Munich, 80336 Munich, Germany, the Institute of Medical Microbiology, Department of Medicine, University of Zurich, 8006 Zurich, Switzerland
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23
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Yu J, Saiardi A, Greenwood JS, Bewley JD. Molecular and biochemical identification of inositol 1,3,4,5,6-pentakisphosphate 2-kinase encoding mRNA variants in castor bean (Ricinus communis L.) seeds. PLANTA 2014; 239:965-77. [PMID: 24463774 DOI: 10.1007/s00425-014-2028-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/09/2014] [Indexed: 06/03/2023]
Abstract
During seed development, phytic acid (PA) associated with mineral cations is stored as phytin and mobilized following germination in support of seedling growth. Two parallel biosynthetic pathways for PA have been proposed; yet the pathway is still poorly understood in terms of its regulation and the enzymes involved. Here, the castor bean (Ricinus communis L.) gene for inositol 1,3,4,5,6-pentakisphosphate 2-kinase (RcIPK1) has been identified. This encodes the enzyme implicated in catalyzing the final reaction in PA biosynthesis, and its expression is enhanced in isolated germinated embryos by application of phosphate and myo-inositol (Ins). Even though only one copy of the RcIPK1 gene is present in the genome, numerous RNA variants are present, most likely due to alternative splicing. These are translated into six closely related protein isoforms according to in silico analysis. Functional analyses using yeast ipk1Δ revealed that only three of the mRNA variants can rescue a temperature-sensitive growth phenotype of this strain. High-performance liquid chromatography (HPLC) analysis of the synthesized inositol phosphates demonstrated that the ability to complement the missing yeast IPK1 enzyme is associated with the production of enzyme activity. The three active isoforms possess unique conserved motifs important for IPK1 catalytic activity.
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MESH Headings
- Base Sequence
- Blotting, Southern
- Ricinus communis/enzymology
- Ricinus communis/genetics
- Ricinus communis/growth & development
- Chromatography, High Pressure Liquid
- Cloning, Molecular
- Computer Simulation
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Plant
- Genes, Plant
- Genetic Complementation Test
- Molecular Sequence Data
- Mutation/genetics
- Phenotype
- Phosphotransferases (Alcohol Group Acceptor)/chemistry
- Phosphotransferases (Alcohol Group Acceptor)/genetics
- Phosphotransferases (Alcohol Group Acceptor)/metabolism
- Phytic Acid/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Saccharomyces cerevisiae/metabolism
- Seeds/enzymology
- Seeds/genetics
- Seeds/growth & development
- Sequence Alignment
- Sequence Analysis, DNA
- Structural Homology, Protein
- Substrate Specificity
- Temperature
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Affiliation(s)
- Jaeju Yu
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
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24
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Pisani F, Livermore T, Rose G, Chubb JR, Gaspari M, Saiardi A. Analysis of Dictyostelium discoideum inositol pyrophosphate metabolism by gel electrophoresis. PLoS One 2014; 9:e85533. [PMID: 24416420 PMCID: PMC3887064 DOI: 10.1371/journal.pone.0085533] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/28/2013] [Indexed: 11/28/2022] Open
Abstract
The social amoeba Dictyostelium discoideum was instrumental in the discovery and early characterization of inositol pyrophosphates, a class of molecules possessing highly-energetic pyrophosphate bonds. Inositol pyrophosphates regulate diverse biological processes and are attracting attention due to their ability to control energy metabolism and insulin signalling. However, inositol pyrophosphate research has been hampered by the lack of simple experimental procedures to study them. The recent development of polyacrylamide gel electrophoresis (PAGE) and simple staining to resolve and detect inositol pyrophosphate species has opened new investigative possibilities. This technology is now commonly applied to study in vitro enzymatic reactions. Here we employ PAGE technology to characterize the D. discoideum inositol pyrophosphate metabolism. Surprisingly, only three major bands are detectable after resolving acidic extract on PAGE. We have demonstrated that these three bands correspond to inositol hexakisphosphate (IP6 or Phytic acid) and its derivative inositol pyrophosphates, IP7 and IP8. Biochemical analyses and genetic evidence were used to establish the genuine inositol phosphate nature of these bands. We also identified IP9 in D. discoideum cells, a molecule so far detected only from in vitro biochemical reactions. Furthermore, we discovered that this amoeba possesses three different inositol pentakisphosphates (IP5) isomers, which are largely metabolised to inositol pyrophosphates. Comparison of PAGE with traditional Sax-HPLC revealed an underestimation of the cellular abundance of inositol pyrophosphates by traditional methods. In fact our study revealed much higher levels of inositol pyrophosphates in D. discoideum in the vegetative state than previously detected. A three-fold increase in IP8 was observed during development of D. discoideum a value lower that previously reported. Analysis of inositol pyrophosphate metabolism using ip6k null amoeba revealed the absence of developmentally-induced synthesis of inositol pyrophosphates, suggesting that the alternative class of enzyme responsible for pyrophosphate synthesis, PP-IP5K, doesn’t’ play a major role in the IP8 developmental increase.
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Affiliation(s)
- Francesca Pisani
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Thomas Livermore
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Giuseppina Rose
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Jonathan Robert Chubb
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Marco Gaspari
- Laboratory of Proteomics and Mass Spectrometry, Department of Experimental and Clinical Medicine, “Magna Græcia” University of Catanzaro, Catanzaro, Italy
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- * E-mail:
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Development of low phytate rice by RNAi mediated seed-specific silencing of inositol 1,3,4,5,6-pentakisphosphate 2-kinase gene (IPK1). PLoS One 2013; 8:e68161. [PMID: 23844166 PMCID: PMC3699528 DOI: 10.1371/journal.pone.0068161] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 05/30/2013] [Indexed: 02/03/2023] Open
Abstract
Phytic acid (InsP6) is considered to be the major source of phosphorus and inositol phosphates in most cereal grains. However, InsP6 is not utilized efficiently by monogastric animals due to lack of phytase enzyme. Furthermore, due to its ability to chelate mineral cations, phytic acid is considered to be an antinutrient that renders these minerals unavailable for absorption. In view of these facts, reducing the phytic acid content in cereal grains is a desired goal for the genetic improvement of several crops. In the present study, we report the RNAi-mediated seed-specific silencing (using the Oleosin18 promoter) of the IPK1 gene, which catalyzes the last step of phytic acid biosynthesis in rice. The presence of the transgene cassette in the resulting transgenic plants was confirmed by molecular analysis, indicating the stable integration of the transgene. The subsequent T4 transgenic seeds revealed 3.85-fold down-regulation in IPK1 transcripts, which correlated to a significant reduction in phytate levels and a concomitant increase in the amount of inorganic phosphate (Pi). The low-phytate rice seeds also accumulated 1.8-fold more iron in the endosperm due to the decreased phytic acid levels. No negative effects were observed on seed germination or in any of the agronomic traits examined. The results provide evidence that silencing of IPK1 gene can mediate a substantial reduction in seed phytate levels without hampering the growth and development of transgenic rice plants.
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Abstract
The present review will explore the insights gained into inositol pyrophosphates in the 20 years since their discovery in 1993. These molecules are defined by the presence of the characteristic ‘high energy’ pyrophosphate moiety and can be found ubiquitously in eukaryotic cells. The enzymes that synthesize them are similarly well distributed and can be found encoded in any eukaryote genome. Rapid progress has been made in characterizing inositol pyrophosphate metabolism and they have been linked to a surprisingly diverse range of cellular functions. Two decades of work is now beginning to present a view of inositol pyrophosphates as fundamental, conserved and highly important agents in the regulation of cellular homoeostasis. In particular it is emerging that energy metabolism, and thus ATP production, is closely regulated by these molecules. Much of the early work on these molecules was performed in the yeast Saccharomyces cerevisiae and the social amoeba Dictyostelium discoideum, but the development of mouse knockouts for IP6K1 and IP6K2 [IP6K is IP6 (inositol hexakisphosphate) kinase] in the last 5 years has provided very welcome tools to better understand the physiological roles of inositol pyrophosphates. Another recent innovation has been the use of gel electrophoresis to detect and purify inositol pyrophosphates. Despite the advances that have been made, many aspects of inositol pyrophosphate biology remain far from clear. By evaluating the literature, the present review hopes to promote further research in this absorbing area of biology.
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Barker CJ, Berggren PO. New Horizons in Cellular Regulation by Inositol Polyphosphates: Insights from the Pancreaticβ-Cell. Pharmacol Rev 2013; 65:641-69. [DOI: 10.1124/pr.112.006775] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Synthesis of inositol phosphate ligands of plant hormone-receptor complexes: pathways of inositol hexakisphosphate turnover. Biochem J 2012; 444:601-9. [PMID: 22429240 DOI: 10.1042/bj20111811] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reduction of phytate is a major goal of plant breeding programs to improve the nutritional quality of crops. Remarkably, except for the storage organs of crops such as barley, maize and soybean, we know little of the stereoisomeric composition of inositol phosphates in plant tissues. To investigate the metabolic origins of higher inositol phosphates in photosynthetic tissues, we have radiolabelled leaf tissue of Solanum tuberosum with myo-[2-3H]inositol, undertaken a detailed analysis of inositol phosphate stereoisomerism and permeabilized mesophyll protoplasts in media containing inositol phosphates. We describe the inositol phosphate composition of leaf tissue and identify pathways of inositol phosphate metabolism that we reveal to be common to other kingdoms. Our results identify the metabolic origins of a number of higher inositol phosphates including ones that are precursors of cofactors, or cofactors of plant hormone-receptor complexes. The present study affords alternative explanations of the effects of disruption of inositol phosphate metabolism reported in other species, and identifies different inositol phosphates from that described in photosynthetic tissue of the monocot Spirodela polyrhiza. We define the pathways of inositol hexakisphosphate turnover and shed light on the occurrence of a number of inositol phosphates identified in animals, for which metabolic origins have not been defined.
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Identification of genes necessary for wild-type levels of seed phytic acid in Arabidopsis thaliana using a reverse genetics approach. Mol Genet Genomics 2011. [PMID: 21698461 DOI: 10.1007/s00438‐011‐0631‐2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
Abstract
The majority of phosphorus (P) in seeds is found in phytic acid (InsP(6)) which accumulates as the mixed salt phytate. InsP(6) is generally considered to be an anti-nutrient and the development of low phytic acid (lpa) seed crops is of significant interest. We have employed a reverse genetics approach to examine the impact of disrupting genes involved in inositol phosphate metabolism on Arabidopsis seed InsP(6) levels. Our analysis revealed that knockout mutations in three genes (AtITPK1, AtITPK4, and AtMIK/At5g58730) reduced seed InsP(6) in addition to knockouts of four previously reported genes (AtIPK1, AtIPK2β, AtMRP5, and At5g60760). Seeds of these lpa mutants also exhibited reduced germination under various stress conditions. The greatest reduction in InsP(6) (>70%) was observed in atmrp5 seeds which were also among the least sensitive to the stresses examined. Expression analysis of the lpa genes revealed three distinct patterns in developing siliques consistent with their presumed roles. Disruption of each lpa gene resulted in changes in the expression in some of the other lpa genes indicating that transcription of lpa genes is modulated by other constituents of InsP(6) metabolism. While all the lpa genes represent possible targets for genetic engineering of low phytate seed crops, mutations in AtMRP5, AtMIK, and At5g60760 may be most successful for conventional approaches such as mutation breeding.
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Kim SI, Tai TH. Identification of genes necessary for wild-type levels of seed phytic acid in Arabidopsis thaliana using a reverse genetics approach. Mol Genet Genomics 2011; 286:119-33. [PMID: 21698461 DOI: 10.1007/s00438-011-0631-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 05/27/2011] [Indexed: 11/26/2022]
Abstract
The majority of phosphorus (P) in seeds is found in phytic acid (InsP(6)) which accumulates as the mixed salt phytate. InsP(6) is generally considered to be an anti-nutrient and the development of low phytic acid (lpa) seed crops is of significant interest. We have employed a reverse genetics approach to examine the impact of disrupting genes involved in inositol phosphate metabolism on Arabidopsis seed InsP(6) levels. Our analysis revealed that knockout mutations in three genes (AtITPK1, AtITPK4, and AtMIK/At5g58730) reduced seed InsP(6) in addition to knockouts of four previously reported genes (AtIPK1, AtIPK2β, AtMRP5, and At5g60760). Seeds of these lpa mutants also exhibited reduced germination under various stress conditions. The greatest reduction in InsP(6) (>70%) was observed in atmrp5 seeds which were also among the least sensitive to the stresses examined. Expression analysis of the lpa genes revealed three distinct patterns in developing siliques consistent with their presumed roles. Disruption of each lpa gene resulted in changes in the expression in some of the other lpa genes indicating that transcription of lpa genes is modulated by other constituents of InsP(6) metabolism. While all the lpa genes represent possible targets for genetic engineering of low phytate seed crops, mutations in AtMRP5, AtMIK, and At5g60760 may be most successful for conventional approaches such as mutation breeding.
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Affiliation(s)
- Sang-Ic Kim
- Crops Pathology and Genetics Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Department of Plant Sciences - MS 1, University of California, Davis, CA 95616, USA
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Kim SI, Tai TH. Genetic analysis of two OsLpa1-like genes in Arabidopsis reveals that only one is required for wild-type seed phytic acid levels. PLANTA 2010; 232:1241-1250. [PMID: 20734061 DOI: 10.1007/s00425-010-1243-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 07/28/2010] [Indexed: 05/29/2023]
Abstract
Phytic acid (inositol-1,2,3,4,5,6-hexakisphosphate or InsP(6)) is the primary storage form of phosphorus in plant seeds. The rice OsLpa1 encodes a novel protein required for wild-type levels of seed InsP(6) and was identified from a low phytic acid (lpa) mutant exhibiting a 45-50% reduction in seed InsP(6). OsLpa1 is highly conserved in plants and Arabidopsis contains two OsLpa1-like genes, At3g45090 and At5g60760. Analysis of homozygous T-DNA insertion mutants of At5g60760 revealed significantly reduced levels of seed InsP(6) while no changes were observed in seeds of At3g45090 mutants. A double knockout mutant of At5g60760 and At3g45090 was created and its seed InsP(6) content was similar to that of the At5g60760 mutant indicating that At3g45090 does not provide functional redundancy. OsLpa1 was confirmed to be the ortholog of At5g60760 by complementation of a knockout mutant with a cDNA clone corresponding to the largest of three alternative transcripts of OsLpa1. The spatial and temporal expression of At5g60760 during seed development is consistent with its involvement in seed InsP(6) biosynthesis.
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Affiliation(s)
- Sang-Ic Kim
- US Department of Agriculture, Agricultural Research Service, Department of Plant Sciences, University of California, Davis, CA 95616, USA
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Tsui MM, York JD. Roles of inositol phosphates and inositol pyrophosphates in development, cell signaling and nuclear processes. ACTA ACUST UNITED AC 2009; 50:324-37. [PMID: 20006638 DOI: 10.1016/j.advenzreg.2009.12.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Marco M Tsui
- Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, Box 3813, Durham, NC 27710, USA
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Abstract
The diphosphoinositol polyphosphates ("inositol pyrophosphates") are a specialized subgroup of the inositol phosphate signaling family. This review proposes that many of the current data concerning the metabolic turnover and biological effects of the diphosphoinositol polyphosphates are linked by a common theme: these polyphosphates act as metabolic messengers. This review will also discuss the latest proposals concerning possible molecular mechanisms of action of this intriguing class of molecules.
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Affiliation(s)
- Stephen B Shears
- Inositide Signaling Group, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA.
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35
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Abstract
A highly specific and sensitive mass assay for inositol hexakisphosphate (InsP6) was characterized. This centres around phosphorylating InsP6 with [32P]ATP using a recombinant InsP6 kinase from Giardia lambia, followed by HPLC of the 32P-labelled products with an internal [3H]InsP7 standard. This assay was used to quantify InsP6 levels in a variety of biological samples. Concentrations of InsP6 in rat tissues varied from 10–20 μM (assuming 64% of wet weight of tissue is cytosol water), whereas using the same assumption axenic Dictyostelium discoideum cells contained 352±11 μM InsP6. HeLa cells were seeded at low density and grown to confluence, at which point they contained InsP6 levels per mg of protein similar to rat tissues. This amounted to 1.952±0.117 nmol InsP6 per culture dish, despite the cells being grown in serum shown to contain no detectable (less than 20 pmol per dish) InsP6. These results demonstrate that mammalian cells synthesize all their own InsP6. Human blood was analysed, and although the white cell fraction contained InsP6 at a concentration comparable with other tissues, in serum and platelet-free plasma no InsP6 was detected (<1 nM InsP6). Human urine was also examined, and also contained no detectable (<5 nM) InsP6. These results suggest that dietary studies purporting to measure InsP6 at micromolar concentrations in human plasma or urine may not have been quantifying this inositol phosphate. Therefore claims that administrating InsP6 in the diet or applying it topically can produce health benefits by increasing extracellular InsP6 levels may require reassessment.
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37
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Kim SI, Andaya CB, Newman JW, Goyal SS, Tai TH. Isolation and characterization of a low phytic acid rice mutant reveals a mutation in the rice orthologue of maize MIK. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2008; 117:1291-301. [PMID: 18726583 DOI: 10.1007/s00122-008-0863-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Accepted: 07/31/2008] [Indexed: 05/10/2023]
Abstract
Using a forward genetics approach, we isolated two independent low phytic acid (lpa) rice mutants, N15-186 and N15-375. Both mutants are caused by single gene, recessive non-lethal mutations, which result in approximately 75% (N15-186) and 43% (N15-375) reductions in seed phytic acid (inositol hexakisphosphate). High-performance liquid chromatography and GC-MS analysis of seed extracts from N15-186 indicated that, in addition to phytic acid, inositol monophosphate was significantly reduced whereas inorganic phosphorus and myo-inositol were greatly increased when compared with wild-type. The changes observed in N15-186 resemble those previously described for the maize lpa3 mutant. Analysis of N15-375 revealed changes similar to those observed in previously characterized rice lpa1 mutants (i.e. significant reduction in phytic acid and corresponding increase in inorganic phosphorus with little or no change in inositol phosphate intermediates or myo-inositol). Further genetic analysis of the N15-186 mutant indicated that the mutation, designated lpa N15-186, was located in a region on chromosome 3 between the microsatellite markers RM15875 and RM15907. The rice orthologue of maize lpa3, which encodes a myo-inositol kinase, is in this interval. Sequence analysis of the N15-186 allele of this orthologue (Os03g52760) revealed a single base pair change (C/G to T/A) in the first exon of the gene, which results in a nonsense mutation. Our results indicate that lpa N15-186 is a mutant allele of the rice myo-inositol kinase (OsMIK) gene. Identification and characterization of lpa mutants, such as N15-186, will facilitate studies on the regulation of phytic acid biosynthesis and accumulation and help address questions concerning the contribution of the inositol lipid-dependent and independent biosynthetic pathways to the production of seed phytic acid.
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Affiliation(s)
- S I Kim
- USDA-ARS Crops Pathology and Genetics Research Unit, Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA
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Cho J, King JS, Qian X, Harwood AJ, Shears SB. Dephosphorylation of 2,3-bisphosphoglycerate by MIPP expands the regulatory capacity of the Rapoport-Luebering glycolytic shunt. Proc Natl Acad Sci U S A 2008; 105:5998-6003. [PMID: 18413611 PMCID: PMC2329705 DOI: 10.1073/pnas.0710980105] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Indexed: 11/18/2022] Open
Abstract
The Rapoport-Luebering glycolytic bypass comprises evolutionarily conserved reactions that generate and dephosphorylate 2,3-bisphosphoglycerate (2,3-BPG). For >30 years, these reactions have been considered the responsibility of a single enzyme, the 2,3-BPG synthase/2-phosphatase (BPGM). Here, we show that Dictyostelium, birds, and mammals contain an additional 2,3-BPG phosphatase that, unlike BPGM, removes the 3-phosphate. This discovery reveals that the glycolytic pathway can bypass the formation of 3-phosphoglycerate, which is a precursor for serine biosynthesis and an activator of AMP-activated protein kinase. Our 2,3-BPG phosphatase activity is encoded by the previously identified gene for multiple inositol polyphosphate phosphatase (MIPP1), which we now show to have dual substrate specificity. By genetically manipulating Mipp1 expression in Dictyostelium, we demonstrated that this enzyme provides physiologically relevant regulation of cellular 2,3-BPG content. Mammalian erythrocytes possess the highest content of 2,3-BPG, which controls oxygen binding to hemoglobin. We determined that total MIPP1 activity in erythrocytes at 37 degrees C is 0.6 mmol 2,3-BPG hydrolyzed per liter of cells per h, matching previously published estimates of the phosphatase activity of BPGM. MIPP1 is active at 4 degrees C, revealing a clinically significant contribution to 2,3-BPG loss during the storage of erythrocytes for transfusion. Hydrolysis of 2,3-BPG by human MIPP1 is sensitive to physiologic alkalosis; activity decreases 50% when pH rises from 7.0 to 7.4. This phenomenon provides a homeostatic mechanism for elevating 2,3-BPG levels, thereby enhancing oxygen release to tissues. Our data indicate greater biological significance of the Rapoport-Luebering shunt than previously considered.
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Affiliation(s)
- Jaiesoon Cho
- *Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Social Services, P.O. Box 12233, Research Triangle Park, NC 27709; and
| | - Jason S. King
- Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, United Kingdom
| | - Xun Qian
- *Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Social Services, P.O. Box 12233, Research Triangle Park, NC 27709; and
| | - Adrian J. Harwood
- Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, United Kingdom
| | - Stephen B. Shears
- *Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Social Services, P.O. Box 12233, Research Triangle Park, NC 27709; and
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Suzuki M, Tanaka K, Kuwano M, Yoshida KT. Expression pattern of inositol phosphate-related enzymes in rice (Oryza sativa L.): implications for the phytic acid biosynthetic pathway. Gene 2007; 405:55-64. [PMID: 17961936 DOI: 10.1016/j.gene.2007.09.006] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 08/13/2007] [Accepted: 09/06/2007] [Indexed: 11/29/2022]
Abstract
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.
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Affiliation(s)
- Makoto Suzuki
- Graduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
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Sweetman D, Stavridou I, Johnson S, Green P, Caddick SEK, Brearley CA. Arabidopsis thaliana inositol 1,3,4-trisphosphate 5/6-kinase 4 (AtITPK4) is an outlier to a family of ATP-grasp fold proteins from Arabidopsis. FEBS Lett 2007; 581:4165-71. [PMID: 17698066 DOI: 10.1016/j.febslet.2007.07.046] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Revised: 07/16/2007] [Accepted: 07/19/2007] [Indexed: 10/23/2022]
Abstract
The Arabidopsis genome encodes a family of inositol 1,3,4-trisphosphate 5/6-kinases which form a subgroup of a larger group of ATP-grasp fold proteins. An analysis of the inositol 1,3,4-trisphosphate 5/6-kinase family might, ultimately, be best rewarded by detailed comparison of related enzymes in a single genome. The enzyme encoded by At2G43980, AtITPK4; is an outlier to its family. At2G43980 is expressed in male and female organs of young and mature flowers. AtITPK4 differs from other family members in that it does not display inositol 3,4,5,6-tetrakisphosphate 1-kinase activity; rather, it displays inositol 1,4,5,6-tetrakisphosphate and inositol 1,3,4,5-tetrakisphosphate isomerase activity.
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Affiliation(s)
- Dylan Sweetman
- School of Biological Sciences, University of East Anglia, Earlham Road, Norwich, Norfolk, UK
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42
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Seeds AM, Frederick JP, Tsui MMK, York JD. Roles for inositol polyphosphate kinases in the regulation of nuclear processes and developmental biology. ACTA ACUST UNITED AC 2007; 47:10-25. [PMID: 17467778 PMCID: PMC3258027 DOI: 10.1016/j.advenzreg.2006.12.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
| | | | | | - John D. York
- To whom correspondence should be addressed: Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, DUMC 3813, Durham, NC 27710, Tel: 919-681-6414, Fax: 919-668-0991, E-mail:
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Affiliation(s)
- Victor Raboy
- USDA-ARS and University of Idaho, Aberdeen, Idaho 83210, USA
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Taji T, Takahashi S, Shinozaki K. Inositols and their metabolites in abiotic and biotic stress responses. Subcell Biochem 2006; 39:239-64. [PMID: 17121278 DOI: 10.1007/0-387-27600-9_10] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Teruaki Taji
- Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan
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Stevenson-Paulik J, Chiou ST, Frederick JP, dela Cruz J, Seeds AM, Otto JC, York JD. Inositol phosphate metabolomics: Merging genetic perturbation with modernized radiolabeling methods. Methods 2006; 39:112-21. [PMID: 16829132 DOI: 10.1016/j.ymeth.2006.05.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Accepted: 05/01/2006] [Indexed: 01/22/2023] Open
Abstract
Recent discoveries that provide a link between inositol phosphate (IP) signaling and fundamental cellular processes evoke many exciting new hypotheses about IP function, and underscore the importance of understanding how IP synthesis is regulated. Central to studies of IP metabolism is the essential development of efficient, fast, and reproducible methods for quantitative analysis of IPs in systems ranging from simple cell cultures to more complex tissues and whole organisms. Additionally, in many cases there is a need to pharmacologically and/or genetically alter IP kinase and phosphatase activities in order to visualize low abundance inositol signaling messengers. Here, we describe updated methods for rapid analysis of IP metabolism in normal and genetically manipulated Saccharomyces cerevisiae, Arabidopsis thaliana, Drosophila melanogaster, Mus musculus, and Homo sapiens.
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Affiliation(s)
- Jill Stevenson-Paulik
- Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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York JD. Regulation of nuclear processes by inositol polyphosphates. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:552-9. [PMID: 16781889 DOI: 10.1016/j.bbalip.2006.04.014] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 04/18/2006] [Indexed: 11/18/2022]
Abstract
Inositide signaling pathways represent a multifaceted ensemble of cellular switches capable of regulating a number of processes, for example, intracellular calcium release, membrane trafficking, chemotaxis, ion channel activity and several nuclear functions. Over 30 inositide messengers are found in eukaryotic cells that may be grouped into two classes: (1) inositol lipids, phosphatidylinositols or phosphoinositides (PIPs) and (2) water-soluble inositol polyphosphates (IPs). This review will focus on inositol polyphosphate kinases (IPK) and inositol pyrophosphate synthases (IPS) responsible for the cellular production of IP(4), IP(5) IP(6) and PP-IPs. Of interest, IPK and IPS proteins localize, in part, within the nucleus and their activities are necessary for proper regulation of gene expression, mRNA export, DNA repair and telomere maintenance. The breadth of nuclear processes regulated and the evolutionary conservation of the genes involved in their synthesis have sparked renewed interest in inositide messengers derived from sequential phosphorylation of inositol 1,4,5-trisphosphate.
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Affiliation(s)
- John D York
- Departments of Pharmacology and Cancer Biology and of Biochemistry, Howard Hughes Medical Institute, Duke University Medical Center, Box 3813, Durham, NC 27710, USA.
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47
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Sweetman D, Johnson S, Caddick S, Hanke D, Brearley C. Characterization of an Arabidopsis inositol 1,3,4,5,6-pentakisphosphate 2-kinase (AtIPK1). Biochem J 2006; 394:95-103. [PMID: 16223361 PMCID: PMC1386007 DOI: 10.1042/bj20051331] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metabolic pathway(s) by which plants synthesize InsP6 (inositol 1,2,3,4,5,6-hexakisphosphate) remains largely undefined [Shears (1998) Biochim. Biophys. Acta 1436, 49-67], while the identities of the genes that encode enzymes catalysing individual steps in these pathways are, with the notable exception of myo-inositol phosphate synthase and ZmIpk [Shi, Wang, Wu, Hazebroek, Meeley and Ertl (2003) Plant Physiol. 131, 507-515], unidentified. A yeast enzyme, ScIPK1, catalyses the synthesis of InsP6 by 2-phosphorylation of Ins(1,3,4,5,6)P5 (inositol 1,3,4,5,6-pentakisphosphate). A human orthologue, HsIPK1, is able to substitute for yeast ScIPK1, restoring InsP6 production in a Saccharomyces cerevisiae mutant strain lacking the ScIPK1 open reading frame (ScIpk1Delta). We have identified an Arabidopsis genomic sequence, AtIPK1, encoding an Ins(1,3,4,5,6)P5 2-kinase. Inclusion of the AtIPK1 protein in alignments of amino acid sequences reveals that human and Arabidopis kinases are more similar to each other than to the S. cerevisiae enzyme, and further identifies an additional motif. Recombinant AtIPK1 protein expressed in Escherichia coli catalysed the synthesis of InsP6 from Ins(1,3,4,5,6)P5. The enzyme obeyed Michaelis-Menten kinetics with an apparent V(max) of 35 nmol x min(-1) x (mg of protein)(-1) and a K(m) for Ins(1,3,4,5,6)P5 of 22 microM at 0.4 mM ATP. RT (reverse transcriptase)-PCR analysis of AtIPK1 transcripts revealed that AtIPK1 is expressed in siliques, leaves and cauline leaves. In situ hybridization experiments further revealed strong expression of AtIPK1 in male and female organs of flower buds. Expression of AtIPK1 protein in an ScIpk1Delta mutant strain restored InsP6 production and rescued the temperature-sensitive growth phenotype of the yeast.
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Affiliation(s)
- Dylan Sweetman
- *School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Sue Johnson
- *School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
| | | | - David E. Hanke
- †Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, U.K
| | - Charles A. Brearley
- *School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
- To whom correspondence may be addressed (email )
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Stevenson-Paulik J, Bastidas RJ, Chiou ST, Frye RA, York JD. Generation of phytate-free seeds in Arabidopsis through disruption of inositol polyphosphate kinases. Proc Natl Acad Sci U S A 2005; 102:12612-7. [PMID: 16107538 PMCID: PMC1194928 DOI: 10.1073/pnas.0504172102] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Phytate (inositol hexakisphosphate, IP6) is a regulator of intracellular signaling, a highly abundant animal antinutrient, and a phosphate store in plant seeds. Here, we report a requirement for inositol polyphosphate kinases, AtIPK1 and AtIPK2beta, for the later steps of phytate synthesis in Arabidopsis thaliana. Coincident disruption of these kinases nearly ablates seed phytate without accumulation of phytate precursors, increases seed-free phosphate by 10-fold, and has normal seed yield. Additionally, we find a requirement for inositol tetrakisphosphate (IP4)/inositol pentakisphosphate (IP5) 2-kinase activity in phosphate sensing and root hair elongation. Our results define a commercially viable strategy for the genetic engineering of phytate-free grain and provide insights into the role of inositol polyphosphate kinases in phosphate signaling biology.
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Affiliation(s)
- Jill Stevenson-Paulik
- Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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49
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Williams RSB. Pharmacogenetics in model systems: defining a common mechanism of action for mood stabilisers. Prog Neuropsychopharmacol Biol Psychiatry 2005; 29:1029-37. [PMID: 15950352 PMCID: PMC1249490 DOI: 10.1016/j.pnpbp.2005.03.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/01/2005] [Indexed: 11/18/2022]
Abstract
Defining the underlying causes of psychiatric disorders has provided an ongoing and intractable problem. The analysis of the genetic basis of manic depression, in particular, has been impeded by the absence of a suitable model system and by the lack of candidate causative genes. One recent approach to overcome these problems has involved identifying those genes which control the sensitivity to anti-manic drugs in a model organism. Characterisation of the role of these genes and their encoded proteins in this model has allowed the analysis of their mammalian homologues to elucidate the therapeutic role of these drugs and the possible aetiology of manic depression. This approach has been used successfully with the cellular slime mould, Dictyostelium discoideum. This article introduces the use of model systems for pharmacogenetics research. It describes the identification of prolyl oligopeptidase in D. discoideum as a modulator of inositol phosphate signalling, and the subsequent identification of a common mechanism of action of three anti-manic drugs in mammalian neurons. The use of pharmacogenetics in model systems will provide a powerful tool for the ongoing analysis of both the treatment and cause of psychiatric disorders.
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Key Words
- dictyostelium discoideum
- lithium
- manic depression
- model systems
- pharmacogenetics
- valproic acid
- camp, cyclic adenosine 3′,5′-phosphate
- cbz, carbamazepine
- dag, diacylglycerol
- dpoa, dictyostelium prolyl oligopeptidase
- gsk3/a, glycogen synthase kinase 3/a
- impase, inositol monophosphatase
- insp3, inositol (1,4,5) trisphosphate
- pip2, phosphatidyl-inositol (4,5) bisphosphate
- plc, phospholipase c
- po, prolyl oligopeptidase
- remi, restriction enzyme mediated integration
- vpa, valproic acid
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Affiliation(s)
- Robin S B Williams
- Department of Biology and Wolfson Institute for Biomedical Research, University College London, Gower St., London WC1E 6BT, United Kingdom.
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50
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Shi J, Wang H, Hazebroek J, Ertl DS, Harp T. The maize low-phytic acid 3 encodes a myo-inositol kinase that plays a role in phytic acid biosynthesis in developing seeds. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:708-19. [PMID: 15918884 DOI: 10.1111/j.1365-313x.2005.02412.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Phytic acid, myo-inositol-1,2,3,4,5,6-hexakisphosphate or Ins P6, is the most abundant myo-inositol phosphate in plant cells, but its biosynthesis is poorly understood. Also uncertain is the role of myo-inositol as a precursor of phytic acid biosynthesis. We identified a low-phytic acid mutant, lpa3, in maize. The Mu-insertion mutant has a phenotype of reduced phytic acid, increased myo-inositol and lacks significant amounts of myo-inositol phosphate intermediates in seeds. The gene responsible for the mutation encodes a myo-inositol kinase (MIK). Maize MIK protein contains conserved amino acid residues found in pfkB carbohydrate kinases. The maize lpa3 gene is expressed in developing embryos, where phytic acid is actively synthesized and accumulates to a large amount. Characterization of the lpa3 mutant provides direct evidence for the role of myo-inositol and MIK in phytic acid biosynthesis in developing seeds. Recombinant maize MIK phosphorylates myo-inositol to produce multiple myo-inositol monophosphates, Ins1/3P, Ins4/6P and possibly Ins5P. The characteristics of the lpa3 mutant and MIK suggest that MIK is not a salvage enzyme for myo-inositol recycling and that there are multiple phosphorylation routes to phytic acid in developing seeds. Analysis of the lpa2/lpa3 double mutant implies interactions between the phosphorylation routes.
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Affiliation(s)
- Jinrui Shi
- Crop Genetics Research and Development, Pioneer Hi-Bred International, Inc., Johnston, IA 50131, USA.
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