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Mating behaviour of Nannizzia otae (=Microsporum canis)
Abstract:
One hundred and ninety-eight isolates of Microsporum canis, obtained from humans and animals in 12 countries, were paired with the two Japanese tester strains of Nannizzia otae (= M. canis), VUT 74037 (CDC B-2094+) and VUT 74039 (CDC B-2095-). One hundred and forty-one (72%) produced either gymnothecia or pseudogymnothecia in crosses with VUT 74037. Fifty-seven (28%) were nonreactive. None of the paired isolates reacted with VUT 74039. The number of nonreactive isolates decreased to 17% when 104 of the 198 isolates were paired with one additional tester strain of each mating type. All sexually reacting strains, however, belonged to the (-) mating type. Crosses between nonreactive isolates did not result in ascocarp formation. The F1 generations from three different strongly reactive crosses were all characterized by poor ascospore germination. Most of the monoascospore progeny that germinated to form mature colonies were nonreactive in crosses to determine their mating type. Others reacted predominantly as the (+) mating type, thereby precluding the likelihood of an associated lethal factor accounting for the lack of this mating type in our clinical isolates. Several explanations for this phenomenon are presented.
Insights
Most Microsporum canis isolates from humans and animals are sexually nonreactive, predominantly belonging to the (-) mating type. This study investigates the reasons for the lack of (+) mating type in clinical Microsporum canis isolates.
Area of Science:
- Mycology
- Medical Mycology
- Fungal Genetics
Background:
- Microsporum canis is a significant dermatophyte causing infections in humans and animals.
- Understanding the sexual reproduction of M. canis is crucial for its epidemiological and genetic studies.
- Previous research indicates a prevalence of the (-) mating type in clinical isolates.
Purpose of the Study:
- To investigate the mating compatibility and mating type distribution of M. canis isolates from global sources.
- To explore the reasons behind the observed lack of (+) mating type in clinical M. canis populations.
- To analyze the fertility and progeny characteristics of M. canis sexual crosses.
Main Methods:
- Mating compatibility tests were performed between 198 M. canis isolates and two Japanese tester strains of Nannizzia otae ( = M. canis).
- Additional crosses were conducted with an expanded set of tester strains representing both mating types.
- Ascospore germination and mating type determination of F1 progeny were analyzed.
Main Results:
- 72% of isolates produced sexual structures (gymnothecia or pseudogymnothecia) with the (-) mating type tester strain (VUT 74037).
- No isolates reacted with the (+) mating type tester strain (VUT 74039).
- All sexually reacting strains belonged to the (-) mating type; F1 progeny showed poor germination and predominantly the (+) mating type, suggesting no lethal factor.
Conclusions:
- Clinical isolates of Microsporum canis predominantly exhibit the (-) mating type.
- The lack of (+) mating type in clinical populations is not due to a lethal factor.
- Further research is needed to elucidate the genetic and environmental factors influencing mating type distribution in M. canis.