Inositol phosphates in the duckweed <i>Spirodela polyrhiza</i> L

Brearley, Charles A.; Hanke, David E.

doi:10.1042/bj3140215

Cited by 51 publications

(94 citation statements)

References 37 publications

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“…9) (8). One is an inositol lipid-independent pathway that occurs through sequential phosphorylation of inositol 3-phosphate, or possibly inositol itself, through a series of proposed intermediates based on studies in duckweed and slime mold (13,14). A second is through a phospholipase Cmediated or lipid-dependent pathway that converts PIP 2 to IP 3 and then phytate through multiple routes.…”

Section: Discussionmentioning

confidence: 99%

“…Biochemically, I(1,4,5)P 3 , I(1,3,4,5)P 4 , and I(1,3,4,5,6)P 5 kinase activities have been described in pea roots and immature soybean seeds, respectively, (10 -12), but none of the corresponding genes have been identified. Several studies have indicated that IP 6 may also be synthesized in lipid-independent pathways directly from inositol and/or inosi-tol 3-phosphate (13,14). Despite this, only one IP kinase from any plant species has been cloned and this Arabidopsis gene product has I(1,3,4)P 3 5/6-kinase activity (15).…”

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confidence: 99%

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Molecular and Biochemical Characterization of Two Plant Inositol Polyphosphate 6-/3-/5-Kinases

Stevenson-Paulik

Odom

York

2002

Journal of Biological Chemistry

127

170

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Despite the high deposition of inositol hexakisphosphate (IP 6 ), also known as phytate or phytin, in certain plant tissues little is known at the molecular level about the pathway(s) involved in its production. In budding yeast, IP 6 synthesis occurs through the sequential phosphorylation of I(1,4,5)P 3 by two gene products, Ipk2 and Ipk1, a IP 3 /IP 4 dual-specificity 6-/3-kinase and an inositol 1,3,4,5,6-pentakisphosphate 2-kinase, respectively. Here we report the identification and characterization of two inositol polyphosphate kinases from Arabidopsis thaliana, designated AtIpk2␣ and AtIpk2␤ that are encoded by distinct genes on chromosome 5 and that are ubiquitously expressed in mature tissue. The primary structures of AtIpk2␣ and AtIpk2␤ are 70% identical to each other and 12-18% identical to Ipk2s from yeast and mammals. Similar to yeast Ipk2, purified recombinant AtIpk2␣ and AtIpk2␤ have 6-/3-kinase activities that sequentially phosphorylate I(1,4,5)P 3 to generate I(1,3,4,5,6)P 5 predominantly via an I(1,4,5,6)P 4 intermediate. While I(1,3,4,5)P 4 is a substrate for the plant Ipk2s, it does not appear to be a detectable product of the IP 3 reaction. Additionally, we report that the plant and yeast Ipk2 have a novel 5-kinase activity toward I(1,3,4,6)P 4 and I(1,2,3,4,6)P 5 , which would allow these proteins to participate in at least two proposed pathways in the synthesis of IP 6 . Heterologous expression of either plant isoform in an ipk2 mutant yeast strain restores IP 4 and IP 5 production in vivo and rescues its temperature-sensitive growth defects. Collectively our results provide a molecular basis for the synthesis of higher inositol polyphosphates in plants through multiple routes and indicate that the 6-/3-/5-kinase activities found in plant extracts may be encoded by the IPK2 gene class.Phosphorylation events are a vital part of intracellular communication and enable specific responses to various stimuli. As an asymmetric cyclitol harboring six hydroxyls, myo-inositol is a scaffold that has the potential to transduce a wealth of information through the combinatorial addition of phosphates.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Molecular and Biochemical Characterization of Two Plant Inositol Polyphosphate 6-/3-/5-Kinases

Stevenson-Paulik

Odom

York

2002

Journal of Biological Chemistry

127

170

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“…Several species of floating macrophytes including Spirodela sp. [82] and Azolla sp. [83] have been found to contain either inositol phosphates, enzymes necessary for the synthesis of IHPs, or both.…”

Section: Quantificationmentioning

confidence: 99%

Organic phosphorus in the aquatic environment

Baldwin¹

2013

Environ. Chem.

103

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Environmental context. Organic phosphorus can be one of the major fractions of phosphorus in many aquatic ecosystems. This paper discusses the distribution, cycling and ecological significance of five major classes of organic P in the aquatic environment and discusses several principles to guide organic P research into the future.Abstract. Organic phosphorus can be one of the major fractions of phosphorus in many aquatic ecosystems. Unfortunately, in many studies the 'organic' P fraction is operationally defined. However, there are an increasing number of studies where the organic P species have been structurally characterised -in part because of the adoption of 31 P NMR spectroscopic techniques. There are five classes of organic P species that have been specifically identified in the aquatic environment -nucleic acids, other nucleotides, inositol phosphates, phospholipids and phosphonates. This paper explores the identification, quantification, biogeochemical cycling and ecological significance of these organic P compounds. Based on this analysis, the paper then identifies a number of principles which could guide the research of organic P into the future. There is an ongoing need to develop methods for quickly and accurately identifying and quantifying organic P species in the environment. The types of ecosystems in which organic P dynamics are studied needs to be expanded; flowing waters, floodplains and small wetlands are currently all under-represented in the literature. While enzymatic hydrolysis is an important transformation pathway for the breakdown of organic P, more effort needs to be directed towards studying other potential transformation pathways. Similarly effort should be directed to estimating the rates of transformations, not simply reporting on the concentrations. And finally, further work is needed in elucidating other roles of organic P in the environment other than simply a source of P to aquatic organisms.

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“…Pathways I and II originate from the hydrolysis of PI(4,5)P 2 by phospholipase C and are therefore lipid-dependent. Pathway III is a lipid-independent pathway that involves the sequential phosphorylation of I(3)P or inositol (21,38). The majority of the participating kinases in this pathway are unknown at the molecular level.…”

Section: Atipk1mentioning

confidence: 99%

“…However, the failure to identify a I(1,4,5)P 3 3-kinase activity or gene ortholog in plants has challenged the existence of pathway (II). Pathway (III) has been proposed in Dictyostelium discoideum and Duckweed (21,22), is lipid͞lipase-independent, and occurs through the sequential phosphorylation of I(3)P or free myo-inositol. Recent work has identified a kinase activity with possible relevance to Pathway (III) (23).…”

mentioning

confidence: 99%

Generation of phytate-free seeds in Arabidopsis through disruption of inositol polyphosphate kinases

Stevenson-Paulik

Bastidas

Chiou

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

276

359

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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 AtIPK2␤, 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 (IP 4)͞inositol pentakisphosphate (IP 5) 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.genetically engineered crops ͉ low phytate ͉ signal transduction ͉ phosphate sensing

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Inositol phosphates in the duckweed Spirodela polyrhiza L

Cited by 51 publications

References 37 publications

Molecular and Biochemical Characterization of Two Plant Inositol Polyphosphate 6-/3-/5-Kinases

Molecular and Biochemical Characterization of Two Plant Inositol Polyphosphate 6-/3-/5-Kinases

Organic phosphorus in the aquatic environment

Generation of phytate-free seeds in Arabidopsis through disruption of inositol polyphosphate kinases

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