Ultrastructure of Tube Formation and Basidiospore Development in Ganoderma Lucidum

Abstract

Light microscopy and scanning and transmission electron microscopy were used to study tube for? mation and basidiospore development in Ganoderma lucidum. Young tubes appeared as slight depressions in the tramal surface. Extensive hyphal death and disintegration occurred in association with tube formation. Surviving hyphae in developing tubes became coated with an extracellular matrix. Mature tubes were also coated with this material. Developing basidia pushed through the matrix into the tube lumen where they formed basidiospores. Nuclear migration into spores occurred only after lipid droplets within the spore had begun to coalesce and after spore wall formation had begun. The unique spore wall of G. lucidum appeared to consist of an outermost primary layer, darkly staining inter-wall pillars surrounded by electron transparent regions, and an innermost secondary wall. Wall pillars developed immediately adjacent to the plasma membrane and appeared to displace the primary wall as they developed. The secondary wall then developed between the bases of the wall pillars and the plasma membrane. Wall pillars eventually appeared to fuse with both primary and secondary wall layers but remained as conspicuous structures because of the electron transparent regions around them. Large numbers of detached basidiospores became trapped in tubes. Many were covered by the extracellular matrix and appeared to degenerate.