Ethylene and the regulation of senescence processes in transgenic Nicotiana sylvestris plants.
OBJECTIVE
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.


RESULTS
Fifty percent of the homozygous Pro(35S):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 Pro(35S):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 Pro(35S):ETR1-1 lines and corolla abscission did not take place. When senescence of Pro(35S):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 Pro(35S):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.
Yang
Thomas F
TF
Division of Plant Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire. LE12 5RD.
Gonzalez-Carranza
Zinnia H
ZH
Maunders
Martin J
MJ
Roberts
Jeremy A
JA
D029681:Arabidopsis Proteins / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D035264:Flowers / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000378:metabolism; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011956:Receptors, Cell Surface / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics* / Q000502:physiology*
D029681:Arabidopsis Proteins; C494590:ETR1 protein, Arabidopsis; D005030:Ethylenes; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D002734:Chlorophyll; C036216:ethylene