A Network of HMG-box Transcription Factors Regulates Sexual Cycle in the Fungus Podospora anserina
Figure 4
Crosses of HMG-box gene deletion mutants.
(A) Analysis of male and female fertility of HMG-box gene deletion mutants in crosses with wild-type tester strains. When cultures were confluent, sterile water was poured and dispersed over the surface of the mycelium. As each strain produced spermatia (male cells) and protoperithecia (female organs) regardless of its mating type, reciprocal fertilization of the mutant and wild-type strains took place and indicated whether the mutant was fertile as a male (donor) or as a female (receptor). For ΔPahmg5 some perithecia differentiated at the contact zone where mutant and wild-type mycelia fuse. In the resulting heterokaryotic mycelium, wild-type nuclei complement the male and/or female sterility defect of the mutant. Those perithecia were fertile and expelled numerous asci allowing genetic analysis. (B) Analysis of perithecium distribution in homozygous crosses of HMG-box gene deletion mutants. Fragmented mycelium from mat+ and mat− strains with the same HMG-box deletion were deposited at the center of a Petri dish and incubated until perithecia formed. Typically, the wild-type strains differentiated perithecia within a ring-like area.