Search

Root-knot nematodes, Meloidogyne spp., are sedentary biotrophic parasites which are able to infest > 2000 plant species. After root invasion they settle sedentarily inside the vascular cylinder and maintain a compatible interaction for up to 8 weeks. Plant cells respond to pathogen attacks by producing reactive oxygen species (ROS). These ROS, in particular hydroperoxides, are important regulators of host-parasite interactions and partly govern the success or failure of disease. ROS producing and ROS scavenging enzymes from both the pathogen and the host finely tune the redox state at the host-pathogen interface. We have analysed the gene structure and organization of peroxiredoxins (prx) in Meloidogyne incognita and analysed their role in the establishment of the nematode in its host. Meloidogyne incognita has seven prx genes that can be grouped with other nematode prx into three clades. Clade B prx genes are more actively transcribed in parasitic stages compared with free-living pre-parasitic juveniles. We confirmed in vitro the activity of one of these, Mi-prx2.1, on hydrogen peroxide and butylhydroperoxide. We showed by ultrastructural immunocytochemistry the expression of clade B PRX proteins in the hypodermis and pseudocoelum beneath the tissues directly in contact with the environment, both in free-living and parasitic stages. Finally, knock-down of clade B prx genes led to a significant reduction in the ability of the nematodes to complete their life cycle in the host. The expression of clade B PRX proteins in the tissues in close contact with plant cells during parasitism and the impaired development of nematodes inside the host after clade B prx knock-down suggest an important role for these genes during infection., (Copyright © 2010 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

14-3-3 proteins are highly conserved ubiquitous proteins found in all eukaryotic organisms. They are involved in various cellular processes including signal transduction, cell-cycle control, apoptosis, stress response and cytoskeleton organisation. We report here the cloning of two genes encoding 14-3-3 isoforms from the plant parasitic root-knot nematode Meloidogyne incognita, together with an analysis of their expression. Both genes were shown to be transcribed in unhatched second stage larvae, infective second stage larvae, adult males and females. The Mi-14-3-3-a gene was shown to be specifically transcribed in the germinal primordium of infective larvae, whereas Mi-14-3-3-b was transcribed in the dorsal oesophageal gland in larvae of this stage. The MI-14-3-3-B protein was identified by mass spectrometry in in vitro-induced stylet secretions from infective larvae. The stability and distribution of MI-14-3-3 proteins in host plant cells was assessed after stable expression of the corresponding genes in tobacco BY2 cells.