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Nitrogen-dependent regulation of de novo cytokinin biosynthesis in rice: the role of glutamine metabolism as an additional signal.

ABSTRACT: Cytokinin activity in plants is closely related to nitrogen availability, and an Arabidopsis gene for adenosine phosphate-isopentenyltransferase (IPT), IPT3, is regulated by inorganic nitrogen sources in a nitrate-specific manner. In this study, we have identified another regulatory system of cytokinin de novo biosynthesis in response to nitrogen status. In rice, OsIPT4, OsIPT5, OsIPT7 and OsIPT8 were up-regulated in response to exogenously applied nitrate and ammonium, with accompanying accumulation of cytokinins. Pre-treatment of roots with l-methionine sulfoximine, a potent inhibitor of glutamine synthetase, abolished the nitrate- and ammonium-dependent induction of OsIPT4 and OsIPT5, while glutamine application induced their expression. Thus, neither nitrate nor ammonium, but glutamine or a related metabolite, is essential for the induction of these IPT genes in rice. On the other hand, glutamine-dependent induction of IPT3 occurs in Arabidopsis, at least to some extent. In transgenic lines repressing the expression of OsIPT4, which is the dominant IPT in rice roots, the nitrogen-dependent increase of cytokinin in the xylem sap was significantly reduced, and seedling shoot growth was retarded despite sufficient nitrogen. We conclude that plants possess multiple regulation systems for nitrogen-dependent cytokinin biosynthesis to modulate growth in response to nitrogen availability.

SUBMITTER: Kamada-Nobusada T

PROVIDER: S-EPMC3814184 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Nitrogen-dependent regulation of de novo cytokinin biosynthesis in rice: the role of glutamine metabolism as an additional signal.

Kamada-Nobusada Tomoe T Makita Nobue N Kojima Mikiko M Sakakibara Hitoshi H

Plant & cell physiology 20130920 11

Cytokinin activity in plants is closely related to nitrogen availability, and an Arabidopsis gene for adenosine phosphate-isopentenyltransferase (IPT), IPT3, is regulated by inorganic nitrogen sources in a nitrate-specific manner. In this study, we have identified another regulatory system of cytokinin de novo biosynthesis in response to nitrogen status. In rice, OsIPT4, OsIPT5, OsIPT7 and OsIPT8 were up-regulated in response to exogenously applied nitrate and ammonium, with accompanying accumul ...[more]

PMID: 24058148

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Project description:Purines are molecules essential for many cell processes, including RNA and DNA synthesis, regulation of enzyme activity, protein synthesis and function, energy metabolism and transfer, essential coenzyme function, and cell signaling. Purines are produced via the de novo purine biosynthesis pathway. Mutations in purine biosynthetic genes, for example phosphoribosylaminoimidazole carboxylase/phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS, E.C. 6.3.2.6/E.C. 4.1.1.21), can lead to developmental anomalies in lower vertebrates. Alterations in PAICS expression in humans have been associated with various types of cancer. Mutations in adenylosuccinate lyase (ADSL, E.C. 4.3.2.2) or 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC, E.C. 2.1.2.3/E.C. 3.5.4.10) lead to inborn errors of metabolism with a range of clinical symptoms, including developmental delay, severe neurological symptoms, and autistic features. The pathogenetic mechanism is unknown for these conditions, and no effective treatments exist. The study of cells carrying mutations in the various de novo purine biosynthesis pathway genes provides one approach to analysis of purine disorders. Here we report the characterization of AdeD Chinese hamster ovary (CHO) cells, which carry genetic mutations encoding p.E177K and p.W363* variants of PAICS. Both mutations impact PAICS structure and completely abolish its biosynthesis. Additionally, we describe a sensitive and rapid analytical method for detection of purine de novo biosynthesis intermediates based on high performance liquid chromatography with electrochemical detection. Using this technique we detected accumulation of AIR in AdeD cells. In AdeI cells, mutant for the ADSL gene, we detected accumulation of SAICAR and SAMP and, somewhat unexpectedly, accumulation of AIR. This method has great potential for metabolite profiling of de novo purine biosynthesis pathway mutants, identification of novel genetic defects of purine metabolism in humans, and elucidating the regulation of this critical metabolic pathway.

Dataset Information

Nitrogen-dependent regulation of de novo cytokinin biosynthesis in rice: the role of glutamine metabolism as an additional signal.

Publications

Nitrogen-dependent regulation of de novo cytokinin biosynthesis in rice: the role of glutamine metabolism as an additional signal.

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