Developmental and Structural Section
Choat, B , Chatelet, D.S. , Sun, Q. , Rost, Thomas , Matthews, M.A. .
The role of pit membranes in the movement of Xylella fastidiosa in grape vines.
INTERVESSEL pit membranes are partially hydrolyzed primary cell walls that serve an essential protective function in vascular plants. In eudicots, the nanoscale pores in pit membranes allow the free passage of water and dissolved solutes between vessels but limit the spread of embolisms (gas) and pathogens through the vascular system. The xylem-specific bacteria Xylella fastidiosa causes Pierce’s disease, which is lethal to Vitis vinifera and considered to be one of the greatest threats to viticulture in California. A primary determinant of the ease with which Xylella can move in grape vines is the effectiveness of pit membranes as barriers to bacterial movement. Recent work has shown that long, open conduits exist in the primary xylem of grape vines suggesting that the integrity of pit membranes may have been lost. Additionally, the large scalariform intervessel pit membranes in the secondary xylem of grape vines have many times the surface area pit membranes in species with smaller pits, increasing the chance of naturally occurring large pores. We investigated the ultra-structure and integrity of pit membranes in the primary and secondary xylem of V. vinifera using scanning and transmission electron microscopy, silicon polymer casting, and air seeding. Results indicated that pit membranes of V. vinifera are weaker than those of species with alternate pitting and that this may contribute to the ability of Xylella to move rapidly through the vascular system of grape vines.
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1 - University of California, Davis, Department of Viticulture and Enology, 1 Shields Ave, Davis, California, 95616, USA
2 - University of California Davis, Section of Plant Biology, One Shields Avenue, Davis, California, 95616-8537, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 312/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 11:00 AM