Can You Feel the Love? (Reproduction)

Reproduction in the fungi is really neat, but also very complex. This is especially true of the members of the Ascomycota, like Claviceps purpurea, because they reproduce both sexually and asexually. To give you a better understanding of the general reproduction in the Ascomycota, I'll talk about the general methods of reproduction in this phylum. Sexual reproduction occurs when two compatible mycelia undergo plasmogamy. This just means that they fuse their cytoplasm together, but they DO NOT fuse their nuclei quite yet. This means that the cells are in the dikaryotic, or "N+N" stage; a state found only in the fungi. From here, the fungi grow until an environmental factor tells them to make a fruiting body. Within the fruiting body we have karyogamy, the fusion of the nuclei, and then the ascospores are produced in the ascus after the newly diploid cell undergoes one round of meiosis followed by one round of mitosis to form eight ascospores. These spores are then released into the environment where they can germinate. Like I stated above, there is also asexual reproduction that takes place. When we have asexual reproduction, the fungi produces conidia where they produce spores by simple mitosis.

The lifecycle of this organism is quite complex, like that of most members of the fungi. To describe the lifecycle, I will start with the sclerotium, which is the hardened mass of the fungus' mycelia. The sclerotium is more resistant that normal mycelia, which is important because this is the structure that needs to survive through the winter months. Winter is an important season for this organism and it does best when it has one to two months of cold. When the birds start to chirp and the soil is very moist, the "ergots" start germinating and creating the club-headed fruiting bodies, called stroma. In the fruiting bodies, we have karyogamy and sexual reproduction as described above. These spores are then released through a small hole, called the ostiole, in the perithecium. The spores are then carried by the wind to the flowers of the the open-pollinated grasses. If the plant has not yet been fertilized, Claviceps purpurea infects its host. Once it gets settled in to its new home, it starts to produce structures, called conidia, about a week after infection. Conidia are where the asexual spores are produced externally. Claviceps purpurea produces them in abundance so it can spread to as many plants as possible. It also produces a thick, sticky liquid called honeydew that mixes with the spores so the spores can also be spread by insects. When their time is up, the hardened ergots fall to the ground and start the whole process over again!

Claviceps purpurea is a very serious human pathogen and history shows us how it can create HUGE problems if left unchecked, which makes it important to know when to be most on our guard to watch out for this fungus. Having cool, wet springs is not good because it signals the ergots to germinate and it also delays the process of fertilization. Delaying fertilization is bad because the unfertilized ovaries are the most susceptible to becoming infected with the ergot fungus, in comparison to the pollinated ovaries. For this same reason, having a lot of male sterile plants is bad because there is no pollen being produced. Male sterility is most common in soils that are copper deficient.  

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