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JXB Advance Access first published online on April 25, 2008
This version published online on April 30, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern079
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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

Expression of the β-oxidation gene 3-ketoacyl-CoA thiolase 2 (KAT2) is required for the timely onset of natural and dark-induced leaf senescence in Arabidopsis

Mari Cruz Castillo and José León*

Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), Ciudad Politécnica de la Innovación, Edificio 8E, Avenida del Ingeniero Fausto Elio s/n, E-46022 Valencia, Spain

* To whom correspondence should be addressed. E-mail: jleon{at}ibmcp.upv.es

The onset of leaf senescence is regulated by a complex mechanism involving positive and negative regulators. Among positive regulators, jasmonic acid (JA) accumulates in senescing leaves and the JA-insensitive coi1-1 mutant displays delayed leaf senescence in Arabidopsis. A strong activated expression of the gene coding for the JA-biosynthetic β-oxidation enzyme 3-ketoacyl-CoA thiolase 2 (KAT2) in natural and dark-induced senescing leaves of Arabidopsis thaliana is reported here. By using KAT2::GUS and KAT2::LUC transgenic plants, it was observed that dark-induced KAT2 activation occurred both in excised leaves as well as in whole darkened plants. The KAT2 activation associated with dark-induced senescence occurred soon after a move to darkness, and it preceded the detection of symptoms and the expression of senescence-associated gene (SAG) markers. Transgenic plants with reduced expression of the KAT2 gene showed a significant delayed senescence both in natural and dark-induced processes. The rapid induction of the KAT2 gene in senescence-promoting conditions as well as the delayed senescence phenotype and the reduced SAG expression in KAT2 antisense transgenic plants, point to KAT2 as an essential component for the timely onset of leaf senescence in Arabidopsis.

Key words: Arabidopsis, β-oxidation, jasmonic acid, KAT2, leaf senescence

Received 8 January 2008; Revised 22 February 2008 Accepted 25 February 2008


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