e-journal

High cytokinin levels induce a hypersensitive-like response in tobacco

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† Background and Aims:
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 formationwere investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens.

† Methods:
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 peroxidationwere 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 photosynthesiswere deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange.

† Key Results:
Plants 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.

†Conclusions:
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.

Key words: Cytokinin, hypersensitive response, hydrogen peroxide, lipid peroxidation, pathogenesis-related
proteins, salicylic acid, jasmonic acid, abscisic acid, photosynthesis, stomatal conductance, non-photochemical quenching, Nicotiana tabacum.

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Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

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Penerbit

Oxford : Oxford University Press on behalf of the Annals of Botany Company., 2013

Deskripsi Fisik

Annals of Botany 112: 41–55, 2013

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

EKOLOGI TANAMAN

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

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