THE DEVELOPMENT OF PIERCES DISEASE IN XYLEM: THE ROLES OF VESSEL CAVITATION, CELL WALL METABOLISM AND VESSEL OCCLUSION

• Author(s): Labavitch, John; Matthews, Mark; Greve, Carl; Lurie, Susan; Perez, Alonso; Roper, Caroline; Rost, Thomas; Stevenson, Joshua; Thorne, Eleanor;
• Abstract: This proposal is directed toward discovering the plant responses to infection that are fundamental to the progression of Pierce's disease (PD) in grapevine. The disease is caused by the growth of the bacterium Xylella fastidiosa (X.f.) in the xylem vessels of stems, petioles and leaf blades. The disease progresses rapidly, causing severe water deficits in infected shoots (Goodwin et al., 1988) and vine death-often within two years. However the progression of the disease and the mechanism(s) by which the disease produces water deficits and death in infected tissues have not been well established. The prevailing notion has been that vessels become occluded with bacteria or products of metabolism. However, we have shown that PD symptoms appear in grapevines prior to the development of a large Xf population. However, how the bacterium moves through and between vessels, whether vessels cavitate upon introduction of the bacterium by the insect vector or artificial inoculation, the nature and origin of the materials that occlude the vessels of infected vines, and the nature of the plant regulators that influence the vines response to Xf are not known. We have continued our work testing the model (below) that proposes answers to these important questions about the development and progression of PD symptoms in grapevines. X.f. introduction to vesselsvessel cavitation initial water deficit X.f. population increase production of enzymes by X.f. (signals ?) cell wall digestion oligosaccharide signals ethylene synthesis rise a "wave" of vessel occlusion beyond the infection site global collapse of vine water transport leaf abscissionvine death
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium