In filamentous fungi, vegetative compatibility among individuals of the same species is
determined by the genes encoded at the heterokaryon incompatibility (het) loci. The hyphae of
genetically similar individuals that share the same allelic specificities at their het loci are able to
fuse and intermingle, while different allelic specificities at the het loci result in cell death of the
interacting hyphae. In this study, suppression subtractive hybridization (SSH) followed by
pyrosequencing and quantitative reverse transcription PCR were used to identify genes that are
selectively expressed when vegetatively incompatible individuals of Amylostereum areolatum
interact. The SSH library contained genes associated with various cellular processes, including
cell-cell adhesion, stress and defence responses, as well as cell death. Some of the transcripts
encoded proteins that were previously implicated in the stress and defence responses associated
with vegetative incompatibility. Other transcripts encoded proteins known to be associated with
programmed cell death, but have not previously been linked with vegetative incompatibility.
Results of this study have considerably increased our knowledge of the processes underlying
vegetative incompatibility in Basidiomycetes in general and A. areolatum in particular.