Lipoxygenase in pea roots subjected to biotic stress

Cyst nematode Heterodera goettingiana is a major pest for pea crop. Sources of resistance to this disease have been found in germplasm pea, although the mechanism of host resistance is still obscure. Lipoxygenases (LOX) have been proposed to be involved in the defence of host-parasite interactions. Resistant accession displayed at 24-72 h after nematode infection an incompatible interaction with H. goettingiana characterised by the induction of hypersensitive cell death and induction of LOX activity, mRNA and fatty acid hydroperoxides. In contrast, in susceptible pea roots infected with nematodes the induction of LOX activity, mRNA and fatty acid hydroperoxides was less consistent and delayed and no cell death was observed. A single polypeptide, with an apparent molecular mass of 96 kDa, was identified in both resistant and susceptible either uninfected or infected pea roots. Subcellular localisation showed that immunogold labelling was present in the cytoplasm, vacuoles., and plastids of differentiating parenchyma cells of uninfected and infected roots. Labelling increased weakly in differentiating cells of the feeding sites (syncytia) in susceptible pea at 72 h after infection, and was of greater magnitude in resistant tissues. Our results suggest that LOXs might have a role in root-nematode interaction and in resistance mechanisms. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.