Presenter: Laura C. Hudson
Advisor(s): Eric L. Davis
Author(s): Laura C. Hudson, Candace H. Haigler, and Eric L. Davis
Graduate Program: Plant Pathology, Crop Science, Plant Pathology

Title: ANALYSIS OF CELL WALL SYNTHESIS IN FEEDING CELLS FORMED BY ROOT-KNOT NEMATODES

Abstract: Root-knot nematodes (Meloidogyne sp.) are sedentary endoparasites that infect a wide range of plant species and cause considerable economic loss to many crops. Root-knot nematodes transform selected root vascular cells into enlarged, multinucleate feeding sites called giant-cells that arise from repeated karyokinesis without cytokinesis. Giant-cells undergo extensive modifications of the cell wall architecture including cell wall thickening and the formation of ingrowths that act to increase the surface area of the plasma membrane to facilitate solute uptake. The cell wall growth, expansion, and integrity of giant-cells are hypothesized to be mediated by both cell wall-loosening and cell wall biosynthetic enzymes of plant origin. While the up-regulation of plant genes encoding proteins to promote wall loosening in giant-cells such as endoglucanases, pectinases, extensins, and expansins has been detected, little is known about the process of cell wall deposition in giant-cells. Expression patterns of the plant cellulose synthase (CesA) gene family, whose primary responsibility is cellulose anabolism, are being investigated in feeding site formation during compatible plant-nematode interactions. Ten members of the CesA gene family from Arabidopsis thaliana are being analyzed for expression in giant-cells using RT-PCR. Transgenic Arabidopsis that contain different CesA gene promoter::GUS constructs (kindly provided by M. Doblin and D. Delmer) are also being assayed to monitor CesA expression in giant-cells. Roots of available CesA mutants of Arabidopsis have been infected by root-knot nematodes for functional analyses of the effects of different CesA mutations on the parasitic interaction. The data generated on cell wall deposition can subsequently be integrated with the data on cell wall loosening to provide not only a more comprehensive understanding of the wall architecture of giant-cells, but potentially to serve as a model of the fundamental biology of wall formation in plant cells.