Developmental and Structural Section
Sun, Qiang , Gorzek, Joseph , Sun, Yuliang , Schmitz, Robert , Walker, Andy , Labavitch, John .
Polysaccharide Compositions of Pit Membranes in Grapevines with Different Pierce's Disease Resistance.
Pit membranes (PMs) are the porous cell wall regions (no secondary cell walls) found where two cells contact and communicate with one another. PMs are structurally composed of two thin primary cell walls and one middle lamella. In grapevines, intervessel PMs are the barriers that Xylella fastidiosa cells must pass to achieve intervessel movement and eventual systemic spread in infected vines. Vessel-parenchyma PMs are involved in the formation of vascular occlusions that may contribute to a vine's Pierce's disease (PD) symptom development or resistance. Despite their important role, information about the structure and chemical composition of PMs is still incomplete. We recently developed an immunogold transmission electron microscopy (immunogold-TEM) technique to investigate the ultrastructure and cell wall polysaccharide composition of grapevine PMs. Our data indicate that three types of PMs (i.e., intervessel, interfiber and vessel-parenchyma PMs) have some structural differences. Intervessel PM regions may be compact in appearance as their extended, secondary wall covered regions and may also become swollen or appear loose. Interfiber PMs are also compact but appear thinner than the primary wall extensions that are under the secondary walls. Vessel-parenchyma PMs have a thinner and loose-appearing region facing the vessel lumen, but a compact region toward the parenchyma cell side. With the immunogold-TEM technique, we found that the three PM types in PD-susceptible U0505-35 grapevines differed in the distribution and quantity of fucosylated xyloglucan (XyG). The largest amount of XyG was found at some depth in the interfiber PMs and only a small amount of XyG was detected in the intervessel PMs and in the vessel-parenchyma PMs where the XyG was found toward the vessel side of each PM. Application of our immunogold-TEM technique to intervessel PMs of different grape genotypes has revealed that the intervessel PMs of Chardonnay vines contained a small amount of weakly methyl-esterified homogalacturonans (Me-HGs) randomly distributed across the PMs' width and thickness and that intervessel PMs of U0505-35 and U0505-01 vines have weakly and heavily Me-HGs, respectively, these being restricted to the PM's peripheral regions connecting the wall regions that extend under the secondary walls. These results also demonstrate the immunogold-TEM technique's effectiveness for analysis of the composition and distribution of cell wall polysaccharides across the thickness of a PM.
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1 - University Of Wisconsin-Stevens Point, Department Of Biology, 237 TNR Building, 800 Reserve Street, Stevens Point, WI, 54481, USA
2 - University of Wisconsin-Stevens Point, Department of Biology, Stevens Point, WI, 54481, USA
3 - University of Wisconsin-Madison, Department of Biochemistry, Madison, WI, 53715, USA
4 - University of California-Davis, Department of Viticulture and Enology, Davis, CA, 95616, USA
5 - University of California-Davis, Department of Plant Sciences, Davis, CA, 95616, USA
Cell wall polysaccharides
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM