Chemistry and physiology of an induced plasma membrane cell fusion receptor in the myxomycetes Didymium iridis

Abstract

Cellular fusion is a relatively poorly understood phenomenon. Our efforts to help elucidate membrane components involved in cellular fusion have led us to utilize a model system consisting of haploid myxamoebae of the species "Didymium iridis." Myxamoebae have shown an ability to undergo fusion with cells of the opposite mating type upon obtaining a critical cell density of 1x10 E+5 cells/ml. At this critical density, myxamoebae produce a substance, similar to trisporic acid, that induces the plasma membranes of the cells in such a way as to allow fusion to occur. The resultant fusion yields diploid zygotes which later give rise to free flowing plasmodia. Our research centers on the differences shown between the plasma membrane proteins of the induced (competent to fuse and mate) and the uninduced (incompetent to fuse and mate) haploid myxamoebae. Our laboratory has made antibodies against the induced myxamoebae. Isolated plasma membranes used in conjunction with the aforementioned antibodies have allowed us to form Ab-cell surface protein complexes. Complex formation has been determined by HPLC, electrophoresis, and fluorescence microscopy. Examination of these complexes has allowed us to ascertain which cell surface proteins (glycoproteins) are apparently involved in the process of cellular fusion between haploid myxamoebae of "D. iridis."