IMMUNOGOLD LOCALIZATION OF ARABINOGALACTAN PROTEINS, UNESTERIFIED AND ESTERIFIED PECTINS IN POLLEN GRAINS AND POLLEN TUBES OF NICOTIANA-TABACUM-L

The monoclonal antibodies JIM 5 (against unesterified pectin), JIM 7 (against methyl esterified pectin), MAC 207 (against arabinogalactan proteins, AGPs), and JIM 8 (against a subset of AGPs) were utilized singly or in combinations for immunogold labelling of germinated pollen grains and pollen tubes of Nicotiana tabacum. Pectins were localized in the intine of pollen grain, unesterified pectin being more abundant than the esterified one. AGPs were co-localized with pectin in the intine, but were present preferably close to the plasma membrane. In pollen tubes. AGPs, unesterified and esterified pectins were co-localized in the outer and middle layers of the cell wall. The density of the epitopes was not uniform along the length of the pollen tube, but showed alterations. In the pollen tube tip wall esterified pectin was abundantly present, bur not AGPs. In the cytoplasm esterified pectin and AGPs were detected in Golgi derived vesicles, indicating their role in the pathway of the cell wall precursors. In the ''cell wall'' of generative cell only AGPs: but no pectins were localized. The co-localization of pectins and AGPs in the cell wall of pollen grain and pollen tube might play an important role, not only in maintenance of the cell shape, but also in cell-cell interaction during pollen tube growth and development.