Periodic deposition of arabinogalactan epitopes in the cell wall of pollen tubes of Nicotiana tabacum L.

The monoclonal antibodies MAC 207 and JIM 8, recognizing arabinogalactan epitopes, were used to localize the corresponding antigenic sites in pollen tubes of Nicotiana tabacum L. grown in vitro or semi in vivo. The analysis of the immunofluorescence labelling was performed by means of confocal laser scanning microscopy. Most pollen tubes were labelled along their length, with the exception of the tip region, in a ring-like pattern with remarkable periodicity. The diameter of the rings was approx. 12 μm and the distance between two rings was about 6 μm. No labelling of the cytoplasm, the vegetative nucleus or the generative cell was observed. The presence of labelling in the non-apical tube wall after pectinase and cellulase digestion indicates that the epitopes for MAC 207 and JIM 8 are located in the inner callosic sheath of the pollen-tube wall.