AOBPreview originally published online on September 27, 2007
Annals of Botany 2008 101(2):301-310; doi:10.1093/aob/mcm229
Ethylene and the Regulation of Senescence Processes in Transgenic Nicotiana sylvestris Plants

1 Division of Plant Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire. LE12 5RD
2 Advanced Technologies Cambridge Ltd, Cambridge Science Park, Milton Road, Cambridge, Cambridgeshire, CB4 0WA
* For correspondence. E mail jeremy.roberts{at}nottingham.ac.uk
Received: 30 May 2007 Returned for revision: 25 June 2007 Accepted: 23 July 2007 Published electronically: 27 September 2007
Background and Aims: Exposure of plants to ethylene can influence a spectrum of developmental processes including organ senescence and abscission. The aim of this study was to examine the role of the gaseous regulator in Nicotiana sylvestris plants exhibiting a silenced or constitutive ethylene response.
Methods: Transgenic N. sylvestris plants were generated that either ectopically expressed the Arabidopsis mutant ethylene receptor ETR1-1 or the tomato EIN3-like (LeEIL1) gene. Highly expressing homozygous lines were selected and the time-course of development, from germination to organ senescence, was studied.
Key Results: Fifty percent of the homozygous Pro35S:ETR1-1 lines examined showed a high susceptibility to collapse prior to flowering, with plant death occurring within a few days of leaf wilting. The time-course of leaf senescence in the remaining Pro35S:ETR1-1 lines was visibly arrested compared to wild type (negative segregant) plants and this observation was reaffirmed by chlorophyll and protein analysis. Petal necrosis was also delayed in Pro35S:ETR1-1 lines and corolla abscission did not take place. When senescence of Pro35S:ETR1-1 plants did take place this was accompanied by leaf bleaching, but tissues remained fully turgid and showed no signs of collapse. A single Pro35S:LeEIL1 line was found to exhibit consistently accelerated leaf and flower senescence and precocious flower bud shedding.
Conclusions: These observations support a role for ethylene in regulating a spectrum of developmental events associated with organ senescence and tissue necrosis. Furthermore, the transgenic lines generated during this study may provide a valuable resource for exploring how senescence processes are regulated in plants.
Key words: Nicotiana sylvestris, ethylene, senescence, chlorophyll, flower abscission, etr1-1, necrosis, pathogenesis
Present address: Institute of Plant and Microbial Biology (IPMB) Academia Sinica Nankang, Taipei 11529, Republic of China, Taiwan.
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