Pectins in the cell wall of Arabidopsis thaliana pollen tube and pistil.

Plant sexual reproduction involves the growth of tip-polarized pollen tubes through the female tissues in order to deliver the sperm nuclei to the egg cells. Despite the importance of this crucial step, little is known about the molecular mechanisms involved in this spatial and temporal control of the tube growth. In order to study this process and to characterize the structural composition of the extracellular matrix of the male gametophyte, immunocytochemical and biochemical analyses of Arabidopsis pollen tube wall have been carried out. Results showed a well defined localization of cell wall epitopes with highly esterified homogalacturonan and arabinogalactan-protein mainly in the tip region, weakly methylesterified homogalacturonan back from the tip and xyloglucan and (1→5)-α-L-arabinan all along the tube. Here, we present complementary data regarding 1) the ultrastructure of the pollen tube cell wall and 2) the immunolocalization of homogalacturonan and arabinan epitopes in 16 h-old pollen tubes and in the stigma and the transmitting tract of the female organ. Discussion regarding the pattern of the distribution of the cell wall epitopes and the possible mechanisms of cell adhesion between the pollen tubes and the female tissues is provided.