HETEROTHALLISM

Heterothallism

Ehrenbergh (1829), for the first time studied zygospores in the order Mucorales.  

The American mycologist Blackslee (1904), reported that in the several genera of Mucorales the zygospores are not formed at all. He called “fungi with different mating types are called heterothallic” and fungi without mating types are called homothallic.

Heterothallic fungi are the fungal strains which bear one type of mating type. They are unisexual in nature. Sexual reproduction of heterothallic fungi occurs between two different compatible mycelia. Both mating partners contribute nuclei for the formation of zygote.

Identification of the mating partners is a complex process and it happens via mating type-specific peptide pheromones and receptors. The recognition between compatible mating types is essential for a successful sexual reproduction of heterothallic fungi. These two mating types are similar in morphology and differ genetically and physiologically.

Since heterothallic fungi rely on outcrossing, the genetic variation within the populations is high.  Some heterothallic fungi also exhibit homothallism under specific environmental conditions.  Homothalism – heterothallism transition is found in many fungal species at different environmental conditions.

Examples of heterothallic fungi include Neurospora Crassa,  Saccharomyces cerevisiae, Aspergillus fumigatus, Aspergillus flavus, etc., Neurospora crassa is considered as the most analyzed heterothallic fungal species.

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