Mating in fungi

Mating in fungi is a complex process governed by mating types. Research on fungal mating has focused on several model species with different behaviour. Not all fungi reproduce sexually and many that do are isogamous; thus, the terms "male" and "female" do not apply to many members of the fungal kingdom. Homothallic species are able to mate with themselves, while in heterothallic species only isolates of opposite mating types can mate.

Mating between isogamous fungi may consist only of a transfer of nuclei from one cell to another. Vegetative incompatibility within species often prevent a fungal isolate from mating with another isolate. Isolates of the same incompatibility group do not mate or mating does not lead to successful offspring. High variation has been reported including same chemotype mating, sporophyte to gametophyte mating and biparental transfer of mitochondria.

A zygomycete hypha grows towards a compatible mate and they both form a bridge, called a progametangia, by joining at the hyphal tips via plasmogamy. A pair of septa forms around the merged tips, enclosing nuclei from both isolates. A second pair of septa forms two adjacent cells, one on each side. These adjacent cells, called suspensors provide structural support. The central cell is destined to become a spore. The nuclei join in a process called karyogamy to form a zygote.

As it approaches a mate, a haploid sac fungus develops one of two complementary organs, a "female" ascogonium or a "male" antheridium. These organs resemble gametangia except that they contain only nuclei. A bridge, the trichogyne forms, that provides a passage for nuclei to travel from the antheridium to the ascogonium. A dikaryote grows from the ascogonium, and karyogamy occurs in the fruiting body.

Neurospora crassa is a type of red bread mold of the phylum Ascomycota. N. crassa is used as a model organism because it is easy to grow and has a haploid life cycle that makes genetic analysis simple since recessive traits will show up in the offspring. Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis within a sac-like structure called an ascus (pl. asci). In its natural environment, N. crassa lives mainly in tropical and sub-tropical regions. It often can be found growing on dead plant matter after fires.

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