plant surface microbiology.pdf

5 Cellular Interactions
14 Cellular Ustilaginomycete – Plant Interactions 229
Information concerning the cellular interaction of the Ustilaginomycetes has
come from only a few studies (Mims 1982, 1991; Mims and Nickerson 1986;
Luttrell 1987; Nagler 1989; Nagler et al. 1990; Snetselaar and Tiffany 1990;
Mims et al. 1992; Snetselaar and Mims 1994; Bauer et al. 1995, 1997; Martinez
et al. 1999). Hyphae of the Ustilaginomycetes in contact with host plant cells
possess zones of host–parasite interaction with fungal deposits resulting
from exocytosis of primary interactive vesicles. These zones provide ultrastructural
characters diagnostic for higher groups in the Ustilaginomycetes
(Bauer et al. 1997). Initially, primary interactive vesicles with electron-opaque
contents accumulate in the fungal cell (Fig. 1). Depending on the fungal
species, the primary interactive vesicles may fuse with one another before
being exocytosed from the fungal cytoplasm. Electron-opaque deposits also
Fig. 1. Interactive
vesicles in a hypha of
Exobasidium pachysporum.
Scale bar
0.2 mm