Mitosis and the phylogeny of Taphrina

Abstract

Details of mitosis are described by serial-section EM of synchronized yeast-phase cultures of 5 spp. of Taphrina [T. californica, T. cerasi, T. deformans, T. faulliana and T. polystichi]. Based primarily on the morphology and behavior of the nucleus-associated organelles (NAO) and modes of spindle formation it was concluded that 3 spp. are typical ascomycetes which have some significant differences in their mitotic systems. Each of 2 cultures of a 4th spp., T. deformans, was apparently a mixed culture. An ascomycete type of mitosis was shared by cells of both cultures, but one culture also had cells with another ascomycete mitotic system characterized by elaborate and unique NAO, whereas other cells of the second culture contained a basidiomycete mitotic apparatus. The 5th spp. contained a typical basidiomycetous mitotis system, which indicates that it is misidentified. The detailed differences among the mitotic systems of the true Taphrina species suggest that the genus as a whole is polyphyletic but undoubtedly ascomycetous. However, a previously unreported pattern of spindle formation found in 3 spp. is only otherwise known in a red alga, which may support a common ancestry for the red algae and the ascomycetes. New observations pertinent to the mechanisms of mitosis include, in various species, evidence for splitting of NAO, and their attendant spindle microtubule arrays, during prophase; spindle microtubules polymerization adjacent to the nuclear envelope prior to NAO insertion into the envelope and presence of only 2-4 nonkinetochore microtubules during anaphase-telophase.