Structural character evolution in Pucciniomycotina: mitosis, septa, and hyphal branch initiation in two Helicogloea species

ABSTRACT

Early diverging taxa of Ascomycota and Basidiomycota share similarities in subcellular characters of the spindle pole body (SPB), nuclear division, and septal pore apparatus, but our understanding of character evolution is incomplete because of the limited number of structural studies within the earliest diverging subphyla of Dikarya, Taphrinomycotina and Pucciniomycotina. Two species of Helicogloea (Atractiellomycetes) were analyzed for these characters and provide data on SPB and nuclear division for an additional class of Pucciniomycotina. A detailed analysis of septal pore apparatus for the Helicogloea species permits comparisons with those of other Pucciniomycotina and Ascomycota. The endogenous origin of hyphal branches is shown to occur in a third class of Pucciniomycotina. The full set of characters supports a close relationship between Atractiellomycetes and Pucciniomycetes.

KEY WORDS:

• fungal evolution
• hypha
• microbody
• mitosis
• molecular phylogeny
• septal pore
• ultrastructure

ACKNOWLEDGMENTS

We thank Margaret Birse, Nancy L. Kleven, Eric W.A. Boehm, and the late James C. Doublés for assistance with specimen preparation and data collection, Gail Celio for assistance with figures, Minnesota Supercomputing Institute for support of the AFTOL Structural and Biochemical Database, and University Imaging Centers, University of Minnesota, and acknowledge the contribution of cultures from the late Kenneth Wells and Robert Bandoni. This work was supported by NSF award DEB-0732550 to D.J.M. and DEB-0732968 to M.C.A. as part of the Assembling the Fungal Tree of Life project.

SUPPLEMENTAL MATERIAL

Supplemental data for this article can be accessed on the publisher’s Website.