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Characterization of the inositol monophosphatase gene family in Arabidopsis
Synthesis of myo-inositol is crucial in multicellular eukaryotes for production of phosphatidylinositol and inositol phosphate signaling molecules. The myo-inositol monophosphatase (IMP) enzyme is required for the synthesis of myo-inositol, breakdown of inositol (1,4,5)-trisphosphate, a second messe...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Frontiers Media S.A.
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288329/ https://www.ncbi.nlm.nih.gov/pubmed/25620968 http://dx.doi.org/10.3389/fpls.2014.00725 |
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author | Nourbakhsh, Aida Collakova, Eva Gillaspy, Glenda E. |
author_facet | Nourbakhsh, Aida Collakova, Eva Gillaspy, Glenda E. |
author_sort | Nourbakhsh, Aida |
collection | PubMed |
description | Synthesis of myo-inositol is crucial in multicellular eukaryotes for production of phosphatidylinositol and inositol phosphate signaling molecules. The myo-inositol monophosphatase (IMP) enzyme is required for the synthesis of myo-inositol, breakdown of inositol (1,4,5)-trisphosphate, a second messenger involved in Ca(2+) signaling, and synthesis of L-galactose, a precursor of ascorbic acid. Two myo-inositol monophosphatase -like (IMPL) genes in Arabidopsis encode chloroplast proteins with homology to the prokaryotic IMPs and one of these, IMPL2, can complement a bacterial histidinol 1-phosphate phosphatase mutant defective in histidine synthesis, indicating an important role for IMPL2 in amino acid synthesis. To delineate how this small gene family functions in inositol synthesis and metabolism, we sought to compare recombinant enzyme activities, expression patterns, and impact of genetic loss-of-function mutations for each. Our data show that purified IMPL2 protein is an active histidinol-phosphate phosphatase enzyme in contrast to the IMPL1 enzyme, which has the ability to hydrolyze D-galactose 1-phosphate, and D-myo-inositol 1-phosphate, a breakdown product of D-inositol (1,4,5) trisphosphate. Expression studies indicated that all three genes are expressed in multiple tissues, however, IMPL1 expression is restricted to above-ground tissues only. Identification and characterization of impl1 and impl2 mutants revealed no viable mutants for IMPL1, while two different impl2 mutants were identified and shown to be severely compromised in growth, which can be rescued by histidine. Analyses of metabolite levels in impl2 and complemented mutants reveals impl2 mutant growth is impacted by alterations in the histidine biosynthesis pathway, but does not impact myo-inositol synthesis. Together, these data indicate that IMPL2 functions in the histidine biosynthetic pathway, while IMP and IMPL1 catalyze the hydrolysis of inositol- and galactose-phosphates in the plant cell. |
format | Online Article Text |
id | pubmed-4288329 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | Frontiers Media S.A. |
record_format | MEDLINE/PubMed |
spelling | pubmed-42883292015-01-23 Characterization of the inositol monophosphatase gene family in Arabidopsis Nourbakhsh, Aida Collakova, Eva Gillaspy, Glenda E. Front Plant Sci Plant Science Synthesis of myo-inositol is crucial in multicellular eukaryotes for production of phosphatidylinositol and inositol phosphate signaling molecules. The myo-inositol monophosphatase (IMP) enzyme is required for the synthesis of myo-inositol, breakdown of inositol (1,4,5)-trisphosphate, a second messenger involved in Ca(2+) signaling, and synthesis of L-galactose, a precursor of ascorbic acid. Two myo-inositol monophosphatase -like (IMPL) genes in Arabidopsis encode chloroplast proteins with homology to the prokaryotic IMPs and one of these, IMPL2, can complement a bacterial histidinol 1-phosphate phosphatase mutant defective in histidine synthesis, indicating an important role for IMPL2 in amino acid synthesis. To delineate how this small gene family functions in inositol synthesis and metabolism, we sought to compare recombinant enzyme activities, expression patterns, and impact of genetic loss-of-function mutations for each. Our data show that purified IMPL2 protein is an active histidinol-phosphate phosphatase enzyme in contrast to the IMPL1 enzyme, which has the ability to hydrolyze D-galactose 1-phosphate, and D-myo-inositol 1-phosphate, a breakdown product of D-inositol (1,4,5) trisphosphate. Expression studies indicated that all three genes are expressed in multiple tissues, however, IMPL1 expression is restricted to above-ground tissues only. Identification and characterization of impl1 and impl2 mutants revealed no viable mutants for IMPL1, while two different impl2 mutants were identified and shown to be severely compromised in growth, which can be rescued by histidine. Analyses of metabolite levels in impl2 and complemented mutants reveals impl2 mutant growth is impacted by alterations in the histidine biosynthesis pathway, but does not impact myo-inositol synthesis. Together, these data indicate that IMPL2 functions in the histidine biosynthetic pathway, while IMP and IMPL1 catalyze the hydrolysis of inositol- and galactose-phosphates in the plant cell. Frontiers Media S.A. 2015-01-09 /pmc/articles/PMC4288329/ /pubmed/25620968 http://dx.doi.org/10.3389/fpls.2014.00725 Text en Copyright © 2015 Nourbakhsh, Collakova and Gillaspy. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. |
spellingShingle | Plant Science Nourbakhsh, Aida Collakova, Eva Gillaspy, Glenda E. Characterization of the inositol monophosphatase gene family in Arabidopsis |
title | Characterization of the inositol monophosphatase gene family in Arabidopsis |
title_full | Characterization of the inositol monophosphatase gene family in Arabidopsis |
title_fullStr | Characterization of the inositol monophosphatase gene family in Arabidopsis |
title_full_unstemmed | Characterization of the inositol monophosphatase gene family in Arabidopsis |
title_short | Characterization of the inositol monophosphatase gene family in Arabidopsis |
title_sort | characterization of the inositol monophosphatase gene family in arabidopsis |
topic | Plant Science |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288329/ https://www.ncbi.nlm.nih.gov/pubmed/25620968 http://dx.doi.org/10.3389/fpls.2014.00725 |
work_keys_str_mv | AT nourbakhshaida characterizationoftheinositolmonophosphatasegenefamilyinarabidopsis AT collakovaeva characterizationoftheinositolmonophosphatasegenefamilyinarabidopsis AT gillaspyglendae characterizationoftheinositolmonophosphatasegenefamilyinarabidopsis |