IMMUNOLOCALIZATION OF EXTENSIN AND POTATO-TUBER LECTIN IN CARROT, TOMATO AND POTATO

Tissue-specific expression of two members of the cell wall hydroxyprol ine-rich glycoprotein (HRGP) family, extensin and potato tuber lectin, was examined by immunolocalization at the light microscope level in v arious organs (leaves, stems, roots, fruit, tuber) of carrot (Daucus c arota cv. Thumbelina), tomato (Lycopersicon esculentum cv. Pixie Hybri d II), and potato (Solanum tuberosum cv. Kennebec). Extensin was promi nently expressed in vascular tissue, particularly xylem and also phloe m, although virtually all cells displayed some degree of staining whic h varied as a function of the tissue, organ, and plant under study Ant ibodies against potato tuber lectin (PTL) displayed a localization pat tern similar to that observed for extensin; notably PTL did not stain cambium but did stain epithelial cells lining secretory cavities. Thes e distribution patterns are consistent with a role for extensin, and p ossibly PTL, in providing mechanical support in tissues subjected to c ompression or torsional stress imparted by vascular growth, or by simi lar stress brought about by transport of vascular fluids.