Dataset Information

Dynamics of endogenous cytokinin pools in tobacco seedlings: a modelling approach.

ABSTRACT: Recent advances in cytokinin analysis have made it possible to measure the content of 22 cytokinin metabolites in the tissue of developing tobacco seedlings. Individual types of cytokinins in plants are interconverted to their respective forms by several enzymatic activities (5'-AMP-isopentenyltransferase, adenosine nucleosidase, 5'-nucleotidase, adenosine phosphorylase, adenosine kinase, trans-hydroxylase, zeatin reductase, beta-glucosidase, O-glucosyl transferase, N-glucosyl transferase, cytokinin oxidase). This paper reports modelling and measuring of the dynamics of endogenous cytokinins in tobacco plants grown on media supplemented with isopentenyl adenine (IP), zeatin (Z) and dihydrozeatin riboside (DHZR). Differences in phenotypes generated by the three cytokinins are shown and discussed, and the assumption that substrate concentration drives enzyme kinetics underpinned the construction of a simple mathematical model of cytokinin metabolism in developing seedlings. The model was tested on data obtained from liquid chromatography/tandem mass spectrometry cytokinin measurements on tobacco seedlings grown on Murashige and Skoog agar nutrient medium, and on plants grown in the presence of IP, Z and DHZR. A close match was found between measured and simulated data, especially after a series of iterative parameter searches, in which the parameters were set to obtain the best fit with one of the data sets.

SUBMITTER: Lexa M

PROVIDER: S-EPMC4242250 | biostudies-literature | 2003 Apr

REPOSITORIES: biostudies-literature

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Dynamics of endogenous cytokinin pools in tobacco seedlings: a modelling approach.

Lexa Matej M Genkov Todor T Malbeck Jirí J Machácková Ivana I Brzobohatý Bretislav B

Annals of botany 20030401 5

Recent advances in cytokinin analysis have made it possible to measure the content of 22 cytokinin metabolites in the tissue of developing tobacco seedlings. Individual types of cytokinins in plants are interconverted to their respective forms by several enzymatic activities (5'-AMP-isopentenyltransferase, adenosine nucleosidase, 5'-nucleotidase, adenosine phosphorylase, adenosine kinase, trans-hydroxylase, zeatin reductase, beta-glucosidase, O-glucosyl transferase, N-glucosyl transferase, cytok ...[more]

PMID: 12646503

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Project description:According to the well-documented scenario with regard to the cytokinin-mediated phosphorelay signal transduction in Arabidopsis thaliana, certain members of the type-B ARR family are crucially implicated in the regulatory networks that are primarily propagated by the cytokinin-receptors (AHKs) in response to cytokinin. Nevertheless, clarification of the biological impact of these type-B ARR transcription factors is at a very early stage. Here we focused on a pair of highly homologous ARR10 and ARR12 genes by constructing an arr10 and arr12 double-null mutant. The mutant alleles used in this study were arr10-5 and arr12-1. arr10-5 is the SALK_098604 T-DNA insertion line, whose mutation was determined to be located in the fifth exon of the ARR10 coding sequence. arr12-1 is the SALK_054752 T-DNA insertion line, whose mutation was determined to be located in the third exon of the ARR12 coding sequence. The resulting mutant showed remarkable phenotypes with special reference to the cytokinin-action in roots (e.g., inhibition of root elongation, green callus formation from explants). Furthermore, we demonstrated that ARR10 and ARR12 are involved in the AHK-dependent signaling pathway that modulates the differentiation of root-vascular tissues (i.e., protoxylem-specification), suggesting that ARR10 and ARR12 are the prominent players that act redundantly in the AHK-dependent cytokinin signaling in roots. Keeping this in mind, we then collected the root-specific and combinatorial DNA microarray datasets with regard to the cytokinin-responsible genes by employing both the wild-type and arr10 arr12 double-mutant plants. In this study, wild-type and the arr10 arr12 mutant grown vertically on MS agar plates for 2 weeks were treated with 20 microM of the cytokinin trans-zeatin (TZ) or 0.02% DMSO (solvent for trans-zeatin solution) for 1h. These treated plant samples were divided into three portions, from which RNA samples were prepared separately from roots of seedlings with use of RNeasy Plant Mini Kit (Qiagen, Valencia, CA, U.S.A.). The quality of RNAs prepared was analyzed by Bioanalyzer 2100 (Agilent Technologies). These RNA samples were processed as recommended by the Affymetrix instruction (Affymetrix GeneChip Expression Analysis Technical Manual, Affymetrix). These datasets will provide us with bases for understanding the early response to cytokinin on roots of seedlings in Arabidopsis thaliana.

Project description:In Arabidopsis thaliana, the immediate early response of plants to cytokinin is formulated as the multistep AHK-AHP-ARR phosphorelay signaling circuitry, which is initiated by the cytokinin-receptor histidine protein kinases. In the hope of finding components (or genes) that function downstream of the cytokinin-mediated His-Asp phosphorelay signaling circuitry, we carried out genome-wide microarray analyses. To this end, we focused on a pair of highly homologous ARR10 and ARR12 genes by constructing an arr10 arr12 double null mutant. The mutant alleles used in this study were arr10-5 and arr12-1. arr10-5 is the SALK_098604 T-DNA insertion line, whose mutation was determined to be located in the fifth exon of the ARR10 coding sequence. Arr12-1 is the SALK_054752 T-DNA insertion line, whose mutation was determined to be located in the third exon of the ARR12 coding sequence. The resulting mutant exhibits a characteristic phenotype with regard to the cytokinin-mediated His-Asp phosphorelay. Here we, therefore, compared response to cytokinin in wild type with that in arr10 arr12 double mutant. In this study, wild type and the arr10 arr12 double mutant grown vertically on MS agar plates for 2 weeks were treated with 20uM t-zeatin or 0.02% DMSO (solvent for t-zetion solution) for 1h. These treated plant samples were divided into three portions, from which RNA samples were prepared separately from aerial parts of seedlings with use of RNeasy Plant Mini Kit (Qiagen, Valencia, CA, U.S.A.). The Quality of RNAs prepared was analyzed by Bioanalyzer 2100 (Agilent Technologies). These RNA samples were processed as recommended by the Affymetrix instruction (Affymetrix GeneChip Expression Analysis Technical Manual, Affymetrix). These dataset will provide us with bases for understanding the early response to cytokinin on aerial parts of seedlings in Arabidopsis thaliana. Experimenter name: Hitoshi SAKAKIBARA Experimenter phone: 81455039576 Experimenter fax: 81455039609 Experimenter address: Biodynamics Research Team Experimenter address: RIKEN Plant Science Center Experimenter address: 1-7-22 Suehiro, Tsurumi Experimenter address: Yokohama Experimenter zip/postal_code: 230-0045 Experimenter country: JAPAN Keywords: compound_treatment_design;

Project description:Background and aimsCytokinins are positive regulators of shoot development. However, it has previously been demonstrated that efficient activation of the cytokinin biosynthesis gene ipt can cause necrotic lesions and wilting in tobacco leaves. Some plant pathogens reportedly use their ability to produce cytokinins in disease development. In response to pathogen attacks, plants can trigger a hypersensitive response that rapidly kills cells near the infection site, depriving the pathogen of nutrients and preventing its spread. In this study, a diverse set of processes that link ipt activation to necrotic lesion formation were investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens.MethodsThe binary pOp-ipt/LhGR system for dexamethasone-inducible ipt expression was used to increase endogenous cytokinin levels in transgenic tobacco. Changes in the levels of cytokinins and the stress hormones salicylic, jasmonic and abscisic acid following ipt activation were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Trends in hydrogen peroxide content and lipid peroxidation were monitored using the potassium iodide and malondialdehyde assays. The subcellular distribution of hydrogen peroxide was investigated using 3,3'-diaminobenzidine staining. The dynamics of transcripts related to photosynthesis and pathogen response were analysed by reverse transcription followed by quantitative PCR. The effects of cytokinins on photosynthesis were deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange.Key resultsPlants can produce sufficiently high levels of cytokinins to trigger fast cell death without any intervening chlorosis - a hallmark of the hypersensitive response. The results suggest that chloroplastic hydrogen peroxide orchestrates the molecular responses underpinning the hypersensitive-like response, including the inhibition of photosynthesis, elevated levels of stress hormones, oxidative membrane damage and stomatal closure.ConclusionsNecrotic lesion formation triggered by ipt activation closely resembles the hypersensitive response. Cytokinins may thus act as signals and/or mediators in plant defence against pathogen attack.

Dataset Information

Dynamics of endogenous cytokinin pools in tobacco seedlings: a modelling approach.

Publications

Dynamics of endogenous cytokinin pools in tobacco seedlings: a modelling approach.

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