Journal Article

Cell Wall-Degrading Enzymes Enlarge the Pore Size of Intervessel Pit Membranes in Healthy and Xylella fastidiosa-Infected Grapevines

Kirkpatrick, Bruce, Sun, Qiang, Pérez-Donoso, Alonso G, Greve, L. Carl, Labavitch, John M, Roper, M. Caroline

2010

Overview

The pit membrane (PM) is a primary cell wall barrier that separates adjacent xylem water conduits, limiting the spread of xylem-localized pathogens and air embolisms from one conduit to the next. This paper provides a characterization of the size of the pores in the PMs of grapevine (Vitis vinifera). The PM porosity (PMP) of stems infected with the bacterium Xylella fastidiosa was compared with the PMP of healthy stems. Stems were infused with pressurized water and flow rates were determined; gold particles of known size were introduced with the water to assist in determining the size of PM pores. The effect of introducing trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA), oligogalacturonides, and polygalacturonic acid into stems on water flux via the xylem was also measured. The possibility that cell wall-degrading enzymes could alter the pore sizes, thus facilitating the ability of X. fastidiosa to cross the PMs, was tested. Two cell wall-degrading enzymes likely to be produced by X. fastidiosa (polygalactuoronase and endo-1,4- β -glucanase) were infused into stems, and particle passage tests were performed to check for changes in PMP. Scanning electron microscopy of control and enzyme-infused stem segments revealed that the combination of enzymes opened holes in PMs, probably explaining enzyme impacts on PMP and how a small X. fastidiosa population, introduced into grapevines by insect vectors, can multiply and spread throughout the vine and cause Pierce's disease.

• Publisher: American Society of Plant Biologists
• Subject: acids / air / analogs & derivatives / Bacterial plant pathogens / Biological and medical sciences / Cell Membrane / Cell Membrane - ultrastructure / Cell Wall / Cell Wall - ultrastructure / Cell walls / Cellulase / Cellulase - genetics / Cellulase - metabolism / Edetic Acid / Edetic Acid - analogs & derivatives / embolism / Enzyme Inhibitors / Enzyme Inhibitors - metabolism / Enzymes / enzymology / Fundamental and applied biological sciences. Psychology / genetics / gold / Gold collolid / insect vectors / metabolism / microbiology / Microscopy, Electron, Scanning / particle size / pathogenicity / Phytopathology. Animal pests. Plant and forest protection / Pierce's disease / Plant cells / Plant Diseases / Plant physiology and development / Plant Proteins / Plant Proteins - metabolism / Plant Stems / Plant Stems - microbiology / Plant Stems - ultrastructure / Plants / PLANTS INTERACTING WITH OTHER ORGANISMS / Plants, Genetically Modified / Plants, Genetically Modified - microbiology / Plants, Genetically Modified - ultrastructure / Polygalacturonase / Polygalacturonase - genetics / Polygalacturonase - metabolism / Polysaccharides / Porosity / scanning electron microscopy / stems / ultrastructure / Uronic acids / Vitis / Vitis - metabolism / Vitis - microbiology / Vitis - ultrastructure / Vitis vinifera / Water / Water flow / Xylella / Xylella - enzymology / Xylella - genetics / Xylella - pathogenicity / Xylella fastidiosa / Xylem / Xylem - microbiology / Xylem - ultrastructure