Pollination in Arabidopsis thaliana: Cell-Cell Interaction During Pollen Tube Growth

Abstract

Pollination and the guidance of the pollen tube through the transmitting tract of the gynoecium to the ovule involve a series of complex cell communication events. In this study, we demonstrate that while within the central transmitting tract of the gynoecium, these pollen tubes are tightly adherent to the transmitting tract cells. Once these tubes leave the extracellular matrix (ECM) of the central septum, they adhere to and travel along the ECM of the septum epidermis. The epidermal ECM, which surrounds the pollen tubes, is secreted through breaks in the cuticle of the septum surface. The transmitting tract ECM stains strongly for acidic polysaccharides and stains lightly with the (β-D-Glc)₃ Yariv reagent. Monoclonal antibodies to esterified and low-esterified homogalacturonans do not bind to this ECM. Monoclonal antibodies to arabinogalactan-proteins (AGPs) provide evidence that AGPs may be a component of the septum epidermal ECM (Lennon et al 1998). Preliminary data indicate that in vitro pollen tube growth is inhibited by the addition of the (β-D-Glc)₃ Yariv reagent to the germination medium, though little binding is seen between monoclonal antibodies to AGPs and pollen tubes.