JXB Advance Access originally published online on June 4, 2004
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Journal of Experimental Botany, Vol. 55, No. 402, pp. 1491-1497, July 2004
Journal of Experimental Botany, Vol. 55, No. 402, © Society for Experimental Biology 2004; all rights reserved
RESEARCH PAPER |
Constitutive expression of EIL-like transcription factor partially restores ripening in the ethylene-insensitive Nr tomato mutant*
1Genetic Engineering Research Centre, College of Bioengineering, Chongqing University, Chongqing 400030, PR China
2Waltham Centre for Pet Nutrition, Waltham-on-the-Wolds, Leicestershire, LE14 4RT, UK
3BBSRC Research Group in Plant Gene Regulation, Plant Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5RD, UK
To whom correspondence should be addressed. Fax: +44 (0)115 9516334. E-mail: Donald.Grierson{at}nottingham.ac.uk
Climacteric fruit ripening is regulated by the phytohormone ethylene. ETHYLENE-INSENSITIVE3 (EIN3) is a transcription factor that functions downstream from the ethylene receptors in the Arabidopsis ethylene signal transduction pathway. Three homologues of the Arabidopsis EIN3 gene have been identified in tomato, Lycopersicon esculentum, EIN3-like or LeEIL, LeEIL1, LeEIL2, and LeEIL3. These transcription factors have been proposed to be functionally redundant positive regulators of multiple ethylene responses. In order to test the role of such factors in the ethylene signal transduction pathway during ripening, EIL1 fused to green fluorescent protein (GFP) has been over-expressed in the ethylene-insensitive non-ripening Nr mutant of tomato. Increased levels of LeEIL1 compensated for the normally reduced levels of LeEIL1 in the Nr mutant, and transgenic Nr plants that exhibited high-level constitutive expression of LeEIL1GFP phenotypically resembled wild-type plants, the fruit ripened and the leaves exhibited epinasty, unlike Nr plants. The EIL1GFP fusion protein was located in the cell nuclei of ripe tomato fruit. The mRNA profile of these plants showed that the expression of certain ethylene-dependent ripening genes was up-regulated, including polygalacturonase and TOMLOX B. However, not all ripening genes and ethylene responses, such as seedling triple response, were restored. These results demonstrate that expressing candidate genes in the Nr ethylene-insensitive background is a valuable general approach for testing the role of putative downstream components in the ethylene-signalling pathway.
Key words: Arabidopsis, EIN3, ethylene, signal transduction, tomato
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