|Hanson, Jr., Ronald|
Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2004
Publication Date: 6/1/2004
Citation: McLaughlin, D.L., Hanson, Jr., R.W., Frieders, E.M., Swann, E.C., Szabo, L.J. 2004. Mitosis in the yeast phase of the basidiomycetes Bensingtonia yuccicola and Stilbum vulgare and its phylogenetic implications. American Journal of Botany. 91:808-815. Interpretive Summary: There has been a rapid expansion of the known diversity of yeasts as the range of their potential habitats is being explored. Although generally considered to be ascomycetous fungi, yeasts are also found widely distributed in all three classes of the basidiomycetes. Because their simplicity yields few structural characters, most data used to classify yeasts are molecular or physiological. Microscopic analyses of fungal cells have provided informative characters, such as spindle pole body form, nuclear division features and cytoplasmic organization. Therefore, we have been exploring the mitotic and cytoskeletal patterns of basidiomycetous yeasts as a source of additional phylogenetic characters. Two general mitotic patterns have been found to distinguish ascomycetous and basidiomycetous budding yeasts. In ascomycetous yeasts, mitosis in budding cells occur in the parent, while in basidiomycetous yeasts it occurs in the bud, except in Agaricostilbum pulcherrimum. Phylogenetic analysis of the nuclear small subunit rDNA region showed that A. pulcherrimum as well as two other yeasts (Sterigmatomyces elviase and Stilbum vulgare) are related and all belong in the Agaricostilbomycetidae a subclass of Urediniomycetes. The rust fungi are the largest group within the Urediniomycetes. Immunofluorescence studies showed that S. vulgare had the same mitotic pattern as A. pulcherrimum and supports the molecular analysis. Mitosis in more distantly related yeast, Bensingtonia yuccicola, was shown to occur in the bud. This study provides additional evidence that mitotic and cytoskeletal characters provide phylogenetic information within this group of fungi. Scientists working on the phylogenetics and taxonomy of fungi will use this information.
Technical Abstract: Mitosis in budding cells of ascomycetous yeasts occurs in the parent, while in basidiomyceteous yeasts it occurs in the bud, except in Agaricostilbum pulcherrimum. Investigation of additional yeasts in the Agaricostilbomycetidae of the Urediniomycetes utilized immunofluorescence localization of freeze-substituted material to visualize mitosis. In Stilbum vulgare mitosis occurred in the parent, but in Bensingtonia yuccicola it occurred in the bud as in all other basidiomycetous yeasts studied to date. Stilbum vulgare also exhibited predominantly binucleate yeast cells. Nuclear small subunit rDNA sequence data showed that A. pulcherrimum and S. vulgare are more closely related to each other than to B. yuccicola within the Agaricostilbomycetidae. Based on the few taxa examined, mitotic and cytoskeletal characters provide phylogenetic information.