Schizophyllum mating type test crosses
Test for mating type in Schizophyllum commune This is based on the paper by Papazian (Papazian 1950). Mating type in Schizophyllum is defined by two unlinked loci (matA and matB). Each mating type is multiallelic. A dikaryon thus carries two alleles of each mating type locus and can produce 4 different types of spores (matA-1+matB-1), (matA-2+matB-1), (matA-1+matB-2) and (matA2+matB-2). To test which mating type a spore has, crosses can be performed.
- Use rather thinly poured SMM plates for this.
- Place two monokaryon mycelium plugs about 5mm from each other.
- incubate until the two mycelia together are about 3cm in diameter.
- Check the phenotype.
There are four possibilities:
- No mating type shared (Dikaryon): this can be seen by rugged edges and non-homogeneous growth of the mycelium, often an interaction zone (barrage) between the two mycelia and a the microscopic level clamps.
- same A, different B (common A): no aerial mycelium is formed. Microscopically the mycelium grows with many bumps on it.
- different A, same B (common B): like monokaryon but with barrage between the colonies.
- both A and B same (monokaryon): the two mycelia grow without interaction, and are round and with a smooth edge, with white fluffy mycelium.
The microscopic features can be observed by placing the plate upside down under a microscope with 100x to 200x magnification, depending on the microscope (we have one with a 16x objective that has a larger than normal focal distance which can be used with almost all plates with not too much medium). Or use an inverted microscope.
- Look at the edge of the colony where the mycelium is not too thick.
- Check for clamps at the places where a hypha branches. A clamp is often observable at the opposite side as the branch but in the same plane.
- Common A: bumps and blips are not always present on all hyphae, so scroll around a bit before considering it is not an common A.