Biochemical characterization of Medicago truncatula root knots induced by Meloidogyne incognita
Date
2006
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Root knot nematodes (Meloidogyne spp.) are microscopic endoparasites that infect a broad range of host plants. The goal of this project was to identify protein components of the plant cell wall that are important in root knot formation. The characteristic root knot results from the differentiation of vascular parenchyma into specialized giant cells, as well as the proliferation of adjacent cortical and pericycle cells. The multinucleate giant cells serve as permanent feeding sites within the root and provide nourishment for the developing nematode. Plant cell surface rearrangement occurs during giant cell formation; therefore, I hypothesize these changes are required for the development of giant cells and, thus, are necessary for disease progression. To better study the plant-nematode interaction, a root culture method was developed as a model system for biochemical purification. Using this experimental technique, proteomic analysis was performed to determine how the plant cell wall protein composition changed during the infection process. Proteins were isolated from root knots and uninoculated roots, and separated using 2Dpolyacrylamide gel electrophoresis. Five gel regions were excised and analyzed with tandem mass spectrometry resulting in the identification of thirty-seven proteins whose abundance changes as a result of nematode infection. These proteins mainly represented stress response proteins including PR10-1, glycine-rich RNA binding protein and other proteins involved in plant-microbe interactions. The subcellular localization of a protein, Mt PR10-1, identified in the proteomic study was tested. In addition, the cellular distribution of MtENOD16, an early nodulin involved in the endosymbiotic rhizobia-legume symbiosis, was characterized in root galls using MtENOD/GUS promoter analysis. Furthermore, MtENOD16 was identified in knot cell wall protein fractions suggesting a role in knot formation. These findings have identified and defined protein changes during the course of nematode infection, resulting in an increased understanding of disease progress.