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

Abstract

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-b-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.

Genomic Insights into Xylella fastidiosa Interactions with Plant and Insect Hosts

“…The dramatic differences in the flow speed of different environments (100 to 10,000 times faster inside insect foregut compared to xylem in plants) will have an impact on bacterial cell attachment to surfaces and to each other, since they need to overcome the external shear force stress. In plants, X. fastidiosa multiplies within individual vessels and moves actively to adjacent vessels in the xylem network by producing enzymes that degrade pit membranes separating individual xylem vessels (Perez-Donoso et al 2010). In plant xylem vessels, X. fastidiosa also has a larger surface area to colonize compared to the foregut of leafhoppers (Newman et al 2003).…”

“…Importantly, X. fastidiosa exhibits the ability to actively move against the flow of xylem fluids in vessels by twitching motility (Meng et al 2005). The apparently high efficiency with which cells of X. fastidiosa move through the orifices of pits (Newman et al 2004), which are apparently enlarged due to the action of extracellular enzymes secreted by this pathogen (Perez-Donoso et al 2010), may be due at least in part to its ability to move along surfaces by retraction of the type IV pili. X. fastidiosa also produces relatively short type I pili, encoded by fimA, that apparently act to restrict motility (De La Fuente et al 2007).…”

Developing nanotechnology for biofuel and plant science applications

“…[29] Delivery and release of chemical substances such as phenanthrene and plant growth regulators have also been reported. [30,31] Using the interior pore volume and the exterior surface of MSN along with particle bombardment technology, we previously demonstrated that plasmid DNA carrying a chemically inducible marker gene encoding for green fluorescent protein (GFP) and a chemical inducer (β-oestradiol) could be co-delivered to plant tissues. [3] The controlled release of β-oestradiol led to the expression of GFP in plant cells.…”

“…Investigation into the removal of CO 2 in the presence of water has been an area of active research in recent years. [31][32][33][34] Hicks et al discovered that an interaction between basic surface-bound groups and acidic CO 2 groups resulted in the formation of ammonium bicarbonate and carbonate species. Also being studied was the removal of H 2 S, 35 Cu 2+ , 36 Hg 2+ , 37,38 and Pb 2+ , Mn 2+ , Zn 2+ , Fe 2+ , Cd 2+ , and Ni 2+ .…”

“…Even though bombardment [9][10] , injection [11][12] and ultrasonication [13][14] methods have been used for NP delivery into plant cells, the most common methods involve passive introduction, such as leaf uptake [12,[15][16] , protoplast or tissue incubation and root uptake [17][18][19][20][21][22][23][24][25][26][27][28][29][30] . Because the passive uptake processes of NPs can vary depending on the size [11][12][15][16]31] and properties [32] of NPs and the types of plant tissues or cell structures [33] , it is challenging to control the delivery and function of the NPs in the particular tissues or cells that are targeted.…”