In fungi, sexual reproduction consists of three stages: plasmogamy, karyogamy, and meiosis. While the traditional understanding of sexual reproduction in fungi is that karyogamy occurs immediately after plasmogamy, recent research has demonstrated that this is not always the case.
What is Plasmogamy?
Plasmogamy is the union of two haploid cells. It occurs when cells of two different mating types come into contact and the cell walls dissolve, allowing the two cells to fuse together. In the process, the cytoplasm of the two cells mixes and the nuclei remain separate. This is the first step of sexual reproduction in fungi, and it sets the stage for karyogamy.
What is Karyogamy?
Karyogamy is the fusion of the two nuclei of the two cells that were joined together during plasmogamy. This fusion produces a single cell which contains the genetic content from both of the parent cells. It has twice the amount of genetic material as a haploid cell. This completes the sexual reproduction process in fungi and can lead to the formation of a basidiocarp, or the fruiting body of a fungus.
Why Doesn’t Karyogamy Always Follow Plasmogamy?
Karyogamy does not always immediately follow plasmogamy. This is due to the fact that the two cells often require additional time to prepare for the fusion of their nuclei. This period of time allows for the cells to finish differentiating and for genetic material to be exchanged between the two cells. Furthermore, the surrounding environmental conditions may also have an effect on the timing of karyogamy.
Consequences
The fact that karyogamy does not always immediately follow plasmogamy has many implications. For example, it increases the number of pathways for the evolution of species in fungi. It also allows for a greater amount of genetic diversity within a species as different genetic material is being exchanged between the cells. Finally, this process also provides an additional level of protection against environmental pressures as cells must be physiologically prepared to undergo karyogamy and if they are not, they can delay the process until conditions are more favourable.
Conclusion
In most fungi, karyogamy does not immediately follow plasmogamy. This process has many implications for the evolution of species and the amount of genetic diversity within them. Furthermore, it provides an additional level of protection against environmental pressures, allowing the cells to wait until conditions are more favourable before undergoing karyogamy.