High cytokinin levels induce a hypersensitive-like response in tobacco

0441338 - ÚEB 2015 RIV GB eng J - Journal Article
Novák, J. - Pavlů, J. - Novák, Ondřej - Nožková-Hlaváčková, V. - Špundová, M. - Hlavinka, J. - Koukalová, Š. - Skalák, J. - Černý, M. - Brzobohatý, B.
High cytokinin levels induce a hypersensitive-like response in tobacco.
Annals of Botany. Roč. 112, č. 1 (2013), s. 41-55. ISSN 0305-7364. E-ISSN 1095-8290
R&D Projects: GA MŠMT 1M06030; GA MŠMT LK21306
Institutional support: RVO:61389030
Keywords : Cytokinin * hypersensitive response * hydrogen peroxide
Subject RIV: EB - Genetics ; Molecular Biology
Impact factor: 3.295, year: 2013

Cytokinins 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. The 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. Necrotic 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.
Permanent Link: http://hdl.handle.net/11104/0244369