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JXB Advance Access published online on March 2, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern023
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Silencing polygalacturonase expression inhibits tomato petiole abscission

Cai-Zhong Jiang2, Feng Lu1, Wachiraya Imsabai1, Shimon Meir3 and Michael S. Reid1,*

1Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
2Crops Pathology and Genetics Research Unit, USDA, ARS, One Shields Avenue, Davis, CA 95616, USA
3Department of Postharvest Science of Fresh Produce, ARO, The Volcani Center, Bet Dagan 50250, Israel

* To whom correspondence should be addressed. E-mail: msreid{at}ucdavis.edu

Virus-induced gene silencing (VIGS) was used as a tool for functional analysis of cell wall-associated genes that have been suggested to be involved in leaf abscission. Tobacco rattle virus is an effective vector for VIGS in tomato (Lycopersicon esculentum). Silencing was more efficient when the plants were grown at 22 °C than when they were grown at 20 °C or 25 °C. The photobleaching phenotype resulting from silencing phytoene desaturase varied, depending on cultivar, from barely visible to photobleaching of entire leaves. To study the function of abscission-related genes, a purple transgenic tomato line constitutively expressing the maize anthocyanin regulatory gene, Leaf colour (Lc) was used. Silencing Lc expression in this line resulted in reduced anthocyanin production (reversing the colour from purple to green), thus providing a convenient silencing ‘reporter’. Silencing tomato abscission-related polygalacturonases (TAPGs), using a TAPG1 fragment, delayed abscission and increased break strength of the abscission zone in explants treated with 1 µl l–1 ethylene. The abundance of TAPG1 transcripts in the green (silenced) abscission zone tissues was <1% of that in the purple (non-silenced) controls. As a highly homologous region was used for all five polygalacturonases it is assumed that the effect of delayed abscission is the result of silencing all the genes in this family. By contrast, silencing abscission-related expansins (LeEXP11 and LeEXP12) and endoglucanases (LeCEL1 and LeCEL2) had no discernible effect on break strength, even when the two endoglucanase genes were silenced concurrently. Simultaneous silencing of TAPG and LeCEL1 was no more effective than silencing TAPG alone. The data demonstrate the importance of TAPGs in the abscission of leaf petioles.

Key words: Abscission, cellulase, endoglucanase, expansin, Solanum lycopersicum, polygalacturonase, virus-induced gene silencing

Received 6 November 2007; Revised 11 January 2008 Accepted 16 January 2008


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