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JXB Advance Access first published online on April 2, 2007
This version published online on April 10, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm039
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© 2007 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

9-Lipoxygenase metabolism is involved in the almond/Aspergillus carbonarius interaction

Giovanni Mita1, Pasqua Fasano1, Stefania De Domenico1, Giancarlo Perrone2, Filomena Epifani2, Rina Iannacone3, Rod Casey4 and Angelo Santino1,*

1Institute of Sciences of Food Production CNR Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
2Institute of Sciences of Food Production CNR, Via G. Amendola, 122/O, I-70126 Bari, Italy
3Metapontum Agrobios, SS Jonica 106, Km 448.2, I-75010 Metaponto (MT), Italy
4John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK

* To whom correspondence should be addressed. E-mail: angelo.santino{at}ispa.cnr.it

Phyto-oxylipins are a group of biologically active molecules that play an important role in plant defence. Their production begins with the oxygenation of polyunsaturated fatty acids by lipoxygenases (LOX) to form 9- or 13-hydroperoxides that are substrates for several enzymes involved in the synthesis of final oxylipins, which can act as signal molecules and/or direct antimicrobials. In the present work, the response of the 9-LOX pathway in the almond/Aspergillus carbonarius (producer of ochratoxin A) interaction was studied. Both LOX gene expression and activity are up-regulated over the course of fungal infection in immature and mature almonds. The biochemical characterization of major LOX and hydroperoxide lyase (HPL) isoforms indicated that 9-LOX metabolism is specifically induced by A. carbonarius. Lipid peroxidation profiling showed that, in infected immature almonds, enzymatically produced 9-hydro(peroxy) fatty acids (HFAs) were the main HFAs and are further metabolized by HPL into C9-aldehydes. Both HPL gene expression and C9-aldehydes increased over the course of fungal infection. In mature almonds infected with A. carbonarius, levels of LOX expression and activity were lower than those found in immature seeds, and 9-HFA represented the minority of total HFA, which consisted of mostly 13- and non-enzymatically produced HFA. In these experimental conditions, no volatile aldehydes were recorded from these samples, even though HPL was up-regulated in infected mature almonds. The effects on the growth of A. carbonarius of the aldehydes produced by these enzymes were also tested in vitro. Results reported here led to the proposal that, in almond seed, the association of 9-LOX and HPL has an important role in seed defence mechanism against pathogen infection.

Key words: Almond, Aspergillus carbonarius, lipoxygenase, oxylipins, plant/microbe interaction, volatile aldehydes

Received 21 December 2006; Revised 5 February 2007 Accepted 13 February 2007


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