JXB Advance Access originally published online on September 12, 2005
Journal of Experimental Botany 2005 56(421):2897-2905; doi:10.1093/jxb/eri284
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Mechanisms of the light-dependent induction of cell death in tobacco plants with delayed senescence
Department of Biology, University College London, Gower Street, London WC1E 6BT, UK
* To whom correspondence should be addressed. Fax: +44 (0)20 76797096. E-mail: a.wingler{at}ucl.ac.uk
The relationship between leaf senescence and cell death was investigated using tobacco with delayed senescence due to auto-regulated production of cytokinin (SAG12-IPT). Although leaf senescence ultimately results in cell death, the results show that senescence and cell death can be uncoupled: in nutrient-deficient, but not in fertilized SAG12-IPT plants, necrotic lesions were detected in old, but otherwise green leaves. By contrast, wild-type leaves of the same age were yellow, but not necrotic. Chlorophyll fluorescence analysis revealed an over-reduction of the electron transport chain in old SAG12-IPT leaves, in combination with characteristic spatial patterns of minimum fluorescence (F0), quantum efficiency of open photosystem II centres (Fv/Fm) and non-photochemical quenching (NPQ), as determined by fluorescence imaging. The same patterns of F0, Fv/Fm, and NPQ were induced by incubation of leaf discs from nutrient-deficient SAG12-IPT plants under illumination, but not in the dark, indicating that light-dependent reactions were responsible for the cell death. RT-PCR analysis showed that the pathogenesis-related (PR) genes PR-1b and PR-Q were strongly induced in old SAG12-IPT tobacco leaves with necrotic lesions. In addition, the ethylene-synthesis gene ACO was induced before lesions became visible in SAG12-IPT. It is proposed that over-reduction of the electron transport chain in combination with decreased electron consumption due to nutrient-deficiency led to oxidative stress, which, mediated by ethylene formation, can induce PR gene expression and hypersensitive cell death. Probably as a consequence of inefficient nutrient mobilization, flower development was prematurely aborted and reproduction thereby impaired in nutrient-deficient SAG12-IPT plants.
Key words: Apoptosis, cytokinin, defence, hypersensitive response, oxidative stress, programmed cell death, senescence, tobacco
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  B. Sykorova, G. Kuresova, S. Daskalova, M. Trckova, K. Hoyerova, I. Raimanova, V. Motyka, A. Travnickova, M. C. Elliott, and M. Kaminek Senescence-induced ectopic expression of the A. tumefaciens ipt gene in wheat delays leaf senescence, increases cytokinin content, nitrate influx, and nitrate reductase activity, but does not affect grain yield J. Exp. Bot., February 10, 2008; (2008) erm319v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Masclaux-Daubresse, S. Purdy, T. Lemaitre, N. Pourtau, L. Taconnat, J.-P. Renou, and A. Wingler Genetic Variation Suggests Interaction between Cold Acclimation and Metabolic Regulation of Leaf Senescence Plant Physiology, January 1, 2007; 143(1): 434 - 446. [Abstract] [Full Text] [PDF]
|
|