EFFECTS OF YARIV PHENYLGLYCOSIDE ON CELL-WALL ASSEMBLY IN THE LILY POLLEN-TUBE

Arabinogalactan-proteins (ACPs) are proteoglycans with a high level of galactose and arabinose. Their current functions in plant development remain speculative. In this study, (beta-D-glucosyl)(3) Yariv phenylg lycoside [(beta-D-Glc)(3)] was used to perturb AGPs at the plasmalemma -cell wall interface in order to understand their functional significa nce in cell wall assembly during pollen tube growth. Lily (Lilium long iflorum Thunb.) pollen tubes, in which AGPs are deposited at the tip, were used as a model. Yariv phenylglycoside destabilizes the normal in tercalation of new-cell wall subunits, while exocytosis of the secreto ry vesicles still occurs. The accumulated components at the tip are se gregated between fibrillar areas of homogalacturonans and translucent domains containing callose and AGPs. We propose that the formation of AGP/(beta-D-Glc)(3) complexes is responsible for the lack of proper ce ll wall assembly. Pectin accumulation and callose synthesis at the tip may also change the molecular architecture of the cell wall and expla in the lack of proper cell wall assembly. The data confirm the importa nce of AGPs in pollen tube growth and emphasize their role in the depo sition of cell wall subunits within the previously synthesized cell wa ll.