Short communication Changes in oxylipin synthesis after Phytophthora infestans infection of potato leaves do not correlate with resistance Marie-Laure Fauconnier a, * , Jorge Rojas-Beltran a , Brice Dupuis b , Pierre Delaplace a , Patrick Frettinger a , Virginie Gosset a , Patrick du Jardin a a Plant Biology Unit, Gembloux Agricultural University, Passage des De ´porte ´s 2, 5030 Gembloux, Belgium b Farming Systems Department, Walloon Agricultural Research Centre, Rue de Serpont 100, 6800 Libramont, Belgium Received 30 October 2007 Available online 23 April 2008 Abstract Oxylipins constitute a class of molecules notably involved in hostepathogen interactions. In the potato-Phytophthora infestans (Mont.) De Barry (P. infestans) relationships, the role of colneleic and colnelenic acids, two oxylipins resulting from the consecutive action of lipoxygenase (EC 1.13.11.12) and divinyl ether synthase (EC 1.-) on respectively linoleic and linolenic acids have been previously reported. In the present paper, five potato cultivars with contrasting resistance to P. infestans were submitted to infection. Lipoxygenase pathway response was studied at both transcriptional and metabolic levels. A Northern blot preliminary study revealed that lipoxygenase (lox1 and lox3) and divinyl ether syn- thase genes were clearly up-regulated 96 h after leaf inoculation with P. infestans. Profiling of free and esterified oxylipins performed 24 h, 48 h, 72 h and 96 h after inoculation, showed that esterified oxylipins are mainly produced with 9-derivatives in higher concentrations (esterified forms of colnelenic acid, 9-hydroxy octadecatrienoic acid, 9-hydroperoxy octadecatrienoic acid). Oxylipin accumulation is undetectable 24 h after infection, slightly detectable after 48 h, reaching highest concentrations after 96 h. Cultivars show slightly different oxylipin profiles but the concentration of individual oxylipins differs markedly 96 h after infection. No correlation was found between P. infestans resistance levels and oxylipin synthesis rates or concentration. To assess local and systemic effects of colneleic acid application before P. infestans infection, Bintje cultivar was sprayed with colneleic acid 72 h before inoculation. Both application modes (local and systemic) resulted in lipoxygenase pathway activation without affecting the resistance level to the pathogen. Ó 2008 Elsevier Masson SAS. All rights reserved. Keywords: Lipoxygenase; Oxylipin; Phytophthora infestans; Potato; Solanum tuberosum 1. Introduction Among the various diseases affecting potato crop, late blight is considered as a major threat. Its causing agent is Phy- tophthora infestans (Mont.) De Barry (P. infestans), an oomy- cete fungus [4]. Oxylipins have been shown to be involved in the P. infestans-potato relation [26]. Oxylipin is a collective name for oxidized polyunsaturated fatty acids and their metab- olites. The first step of their metabolic pathway leads to the synthesis of polyunsaturated fatty acid hydroperoxides (HPO) that can be formed enzymatically by lipoxygenase (LOX, EC 1.13.11.12) or a-dioxygenase (EC 1.13.11) or non-enzymatically. Oxygenation of polyunsaturated fatty acids (PUFA) by LOX can occur either at the carbon 9 Abbreviations: CA, colneleic acid; CnA, colnelenic acid; DES, divinyl ether synthase (enzyme); des, divinyl ether synthase (gene); FW, fresh weight; HOD, hydroxyoctadecadienoic acid; HOT, hydroxyoctadecatrienoic acid; HPL, hydroperoxide lyase (enzyme); hpl, hydroperoxide lyase (gene); HPLC, high-performance liquid chromatography; HPO, polyunsaturated fatty acid hydroperoxide; HPOD, hydroperoxy octadecadienoic acid; HPOT, hydro- peroxy octadecatrienoic acid; LOX, lipoxygenase (enzyme); lox1, lipoxyge- nase 1 (gene); lox2, lipoxygenase 2 (gene); lox3, lipoxygenase 3 (gene); Me, esterified form; P. infestans, Phytophthora infestans; PUFA, polyunsaturated fatty acid. * Corresponding author. Tel: þ32 81 622460; fax: þ32 81 600727. E-mail address: fauconnier.ml@fsagx.ac.be (M.-L. Fauconnier). 0981-9428/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2008.04.010 Available online at www.sciencedirect.com Plant Physiology and Biochemistry 46 (2008) 823e831 www.elsevier.com/locate/plaphy