Pectin distribution at the surface of potato parenchyma cells in relation to cell-cell adhesion

The crispness of fruits and vegetables is dependent, predominantly, on the maintenance of cell adhesion. There is a growing body of evidence to sugges t that cell adhesion in plants is controlled at the edge of cell faces rath er than across the entire cell surface. The aim of the current study has be en to exploit antibody-labeling techniques in conjunction with methods that induce cell separation to explore the distribution of highly esterified an d weakly esterified pectic polysaccharides on the cell surface. Potato pare nchyma tissue was subjected to cooking and chemical treatments, which induc ed softening through cell separation. Scanning electron microscopy (SEM) re vealed characteristic patterns on the surface of these separated cells, whi ch outlined the imprint of neighboring cells. Monoclonal antibodies, JIM5 a nd JIM7, were used to locate weakly esterified and highly esterified pectin by silver-enhanced immunogold SEM. The edge-of-face structures labeled str ongly with JIM5 but not JIM7, indicating that they contained polygalacturon ic acid of low ester content. In addition, adhesion of the middle lamella t o the face of the primary wall was found to differ from adhesion at the edg e of each cell face. This, in conjunction with the antibody-labeling observ ations, complements previous transmission electron microscopy studies and i s consistent with the edge-of-face regions having a specialist role in cell adhesion.