SEQUENTIAL DEPOSITION OF PLANT GLYCOPROTEINS AND POLYSACCHARIDES AT THE HOST-PARASITE INTERFACE OF UROMYCES-VIGNAE AND VIGNA-SINENSIS - EVIDENCE FOR ENDOCYTOSIS AND SECRETION

Monokaryotic haustoria (M-haustoria) of Uromyces vignae in Vigna sinen sis cells are surrounded by an extrahaustorial matrix (ema) and the in vaginated host plasmalemma, the extrahaustorial membrane (ehm). The em a was characterized with antibodies against components of the plant ce ll wall; the ema contained hydroxyproline-rich glycoproteins and arabi nogalactans/arabinogalactan proteins, both at a higher concentration c lose to the ehm. Haustoria with large vacuoles had the ema encased by additional layers. An electron-translucent inner layer deposited on to p of the ema contained arabinogalactans/arabinogalactan proteins, hydr oxyproline-rich glycoproteins, and callose. The inner layer was surrou nded by an electron-translucent middle layer with numerous dark inclus ions, rich in pectin and fucose bound to xyloglucans. Finally, a more electron-dense outer layer containing arabinogalactans/arabinogalactan proteins and hydroxyproline-rich glycoproteins encased the whole stru cture. These polysaccharides, with the exception of callose and un-est erified pectin, were also found in the plant Golgi apparatus. The poly saccharides were synthesized in the trans Golgi cisternae and secreted into the host-parasite interface. The secretory events seem to be cou pled to endocytosis since numerous coated pits were found on the ehm t oo. The pits were elongated, sometimes formed tubules and the coat rea cted with an antibody against plant clathrin. Our results suggest inte nsive membrane recycling around haustoria, together with the secretion of cell wall material, which in the case of more or less vacuolated h austoria seems to be responsible for encasement