During my stay at the Department of Biochemistry (Plant Molecular Biology) at University of Turku my research has concentrated on the molecular and cell biology of sexual reproduction of mushrooms (filamentous basidiomycetes). The model mushroom in the research is the wood degrading basidiomycete Schizophyllum commune. The sexual reproduction of mushrooms is regulated by the genes at A mating type locus encoding homeodomain transcription factors and those at B locus encoding a pheromone/receptor system. At mating of haploid strains with different A and B genes the pheromone-receptor interaction induces the reciprocal nuclear exchange between the mates which then results into the growth of a dikaryon (functionally diploid mycelium) regulated by A genes. My research clarifies the role of cytoskeleton in the development of dikaryotic mycelium with fruiting bodies.

At the reciprocal nuclear exchange and migration the nuclei move with a speed 10 to 20 times the hyphal growth rate between the haploid partners with different B genes. The extensive microtubule tracks seen in migration hyphae around nuclei suggest that microtubules and together with microtubule associated motors are used in the intercellular nuclear exchange and migration. The function of ten kinesins, performing mainly plus-end directed transport, and one dynein, for minus-end directed transport identified in the S. commune genome require further investigation for their role in nuclear movement at mating.
Recently, the live cell imaging has revealed that actin cytoskeleton plays a significant role in maintaining the two nuclei with different mating type genes paired and synchronously dividing in dikaryon. Actin cytoskeleton is also necessary for The immediate formation of cross wall after nuclear division. Different factors regulating the actin cytoskeleton in nuclear pairing and in signaling between karyokinesis and cytokinesis are searched for. A central question is also the interaction between actin and microtubule cytoskeleton. All these functions are regulated directly or indirectly by A and B mating type genes.
The described mating type system concerns growth and sexual reproduction of more than 5000 important fungal species recycling organic matter, forming mycorrhiza and being pathogenic for plants and human.