Double-membraned vesicles and their possible role in the ontogeny of microbodies of Basidiobolus haptosporus.
A concomitant but transient occurrence of large numbers of double-membraned vesicles with immature, culturally induced microbodies was demonstrated in thin sections of Basidiobolus haptosporus soon after transfer of the fungus to a defined medium containing xanthine or its catabolites as the sole source of nitrogen. Double-membraned vesicles were rapidly formed as derivatives of endoplasmic cisternae later to occur free in the cytoplasm, often as the most predominant cytoplasmic inclusion. Densitometric measurements revealed that heavy metal-binding cytoplasmic constituents were concentrated within the vesicular lumen. Most of the double-membraned vesicles appeared to undergo degeneration; they were rare to absent in thin sections of older cells. At times, double-membraned vesicles were seen connected to newly formed microbodies in a manner suggesting ontogenic relationships. The outer vesicular membrane was continuous with the single limiting membrane of the microbody via a short tubule. We interpret these observations as empirical ultrastructural evidence to suggest that some double-membraned vesicles become specialized and function as precursor inclusions in the biogenesis of new microbody populations committed to purine salvage.
Fiskin
A M
AM
Research Service, Veterans Administration Medical Center, Kansas City, MO 64128.
Garrison
R G
RG
D001487:Basidiomycota / Q000648:ultrastructure*; D003720:Densitometry; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D008566:Membranes / Q000648:ultrastructure*; D008830:Microbodies / Q000648:ultrastructure*; D008854:Microscopy, Electron; D001678:Organelle Biogenesis; D011687:Purines / Q000378:metabolism
D011687:Purines