AN IMPROVED PROCEDURE FOR THE ISOLATION OF PLASMODESMATA EMBEDDED IN CLEAN MAIZE CELL-WALLS

A cell wall preparation of high purity was obtained using a procedure which involved repeated grindings of etiolated maize mesocotyl tissue and filtration through 200 mesh nylon cloth, followed by cell disruption via a nitrogen disruption bomb, and recovery of the cell walls via filtration. The cell wall fraction was free of particulate contaminants as determined both by phase-contrast and electron microscopy. The only membrane components found associated with the wall fraction as determined by electron microscopy were pladmodesmata embedded in the cell wall. The specific concentration of PAP26, a plasmodesmatal-associated polypeptide, was greatly increased in the cleanest cell wall fraction. A second plasmodesmatal-associated protein, PAP27, which was previously shown to be associated with the neck region of the plasmodesmata, was diminished as a result of passage through the nitrogen disruption bomb suggesting a partial fragmentation of the plasmodesmata. In addition to PAP26, the specific concentrations of at least three other cell wall-associated polypeptides with molecular weights of 80, 21 and 18 kDa, as revealed by SDS-PAGE, were also increased greatly in the cleanest cell wall fraction.