Golgi vesicles fused with invaginated plasma membranes in host cells treated with a host-specific toxin from the Japanese pear pathotype of Alternaria alternata.

Abstract

The secretory activity of Golgi bodies in Japanese pear leaves treated with AK-toxin was examined with an electron microscope by staining sections with alkaline bismuth stain as a tracer of Golgi vesicles to discern the viability of the toxin-treated susceptible cells. The toxin caused the invaginations of plasma membranes and the loss of abundant membranous fragments from the invaginated plasma membranes in the susceptible cells. In the susceptible cells treated with the toxin for 1, 3, and 6hr, many Golgi vesicles which were positive to alkaline bismuth stain were present at the peripheral cytoplasm beneath invaginated plasma membranes and some of them fused with the invaginated plasma membranes. The accumulation and fusion of the Golgi vesicles were rarely found in cells of the necrotic susceptible leaves treated with the toxin for 10hr. However, the phenomena were not observed in the toxin-treated resistant cells and the water-treated susceptible ones. The susceptible cells were viable within 6hr after the toxin treatment because the cells had the high activity of Golgi bodies and the high ability of plasma membranes to fuse with many Golgi vesicles. On the contrary, the susceptible cells appeared not to be viable 10hr after the treatment because they had both the low activity of Golgi bodies and the poor ability of plasma membranes. The results indicate that the enhanced production of Golgi vesicles may be associated with the viability of cells in the toxin-treated susceptible leaves, and that the produced Golgi vesicles may be supplied for repairing the damaged plasma membranes.