Nuclear architecture and DNA location in two VAM fungi

The ultrastructural organization of nuclei in Glomus versiforme and G. mosseae hyphae was examined by sampling at different times during the fungus life cycle. In young and active hyphae, the nucleus is chromocentric with dispersed chromatin and a well-developed nucleolus. On aging, and particularly during arbuscule collapse, the chromatin condenses to give a pyk-notic nucleus with blebs in the envelope and conspicuous spaces between this and the nucleoplasm. DNA location by immunogold or enzyme-gold techniques resulted in uniform labelling over the chromatin. Nuclear degeneration is mirrored by decreased gold labelling and may thus be regarded as an important parameter for evaluation of fungus viability and the ephemeral life of the arbuscule.