Fungal Life Cycle - Summary General Biology PDF

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This review will follow the life cycle of a basidiomycete as a guide to the generalized fungal life cycle...

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Fungal Life Cycle This review will follow the life cycle of a basidiomycete as a guide to the generalized fungal life cycle General Terms  Mycelium – the main body of the fungus (located under ground)  Hyphae – filaments/ thread-like structures of the fungus which grow together into a kind of mat, which we call the mycelium  Spore – the generative product of fungal reproduction; it is haploid and can grow into another mycelium when it lands on a suitable substrate  Haploid – term referring to the state in which cell nuclei contain only one set of the organism’s chromosomes (often abbreviated as “n” or “1n” )  Diploid – term referring to the state in which cell nuclei contain two sets of the organism’s chromosomes (often abbreviated as “2n”)  Dikaryotic – term referring to the state in which the organism’s cells contain two nuclei (each with one set of chromosomes) that are not fused (often abbreviated as “n+n”  Plasmogamy – the reproductive process by which mycelia of appropriate mating types contact each other and fuse their cytoplasm  Karyogamy – the reproductive process by which the complimentary haploid nuclei of a dikaryotic fungus fuse together to produce diploid nuclei Life Cycle 1. The fungal life cycle begins when two haploid hyphae of appropriate mating types (often depicted as + and –) come into contact with each other. 2. The two hyphae then undergo plasmogamy, fusing their cytoplasm and creating cells with two haploid nuclei- one with the “+” set of genetic information and one with the “–” set. The product of this process is dikaryotic, and the fused dikaryotic hyphae grow into a mycelium. 3. When conditions are correct, the dikaryotic mycelium sprouts a mushroom (basidiocarp) which grows above the ground. 4. In the gills on the underside of the mushroom cap, there are structures called basidia. In each basidium, there are two haploid nuclei, one each with the genetic information from the “+” and “–” mating type. 5. Inside the basidia, the “+” and “–” haploid nuclei fuse to create diploid nuclei in the process called karyogamy. 6. The diploid product of karyogamy then divides by meiosis to produce four haploid nuclei which develop into spores. The meiosis in this step provides the genetic shuffling which is the goal of sexual reproduction. 7. Eventually, the basidia release the spores which are carried by the wind and dispersed.

8. When the spores land on an appropriate substrate, they germinate and grow into haploid hyphae. The hyphae grow and eventually contact hyphae of the opposite mating type, beginning the cycle again.

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