Oxylipins constitute a class of molecules notably involved in host-pathogen 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 synthase genes were clearly up-regulated 96h after leaf inoculation with P. infestans. Profiling of free and esterified
oxylipins performed 24h, 48h, 72h and 96h 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 24h after
infection, slightly detectable after 48h, reaching highest concentrations after 96h. Cultivars show slightly different
oxylipin profiles but the concentration of individual
oxylipins differs markedly 96h 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 72h before inoculation. Both application modes (local and systemic) resulted in
lipoxygenase pathway activation without affecting the resistance level to the pathogen.