Notes: This is a compilation of information derived from another post I started at another board about a year ago (11.2002). I hope someone finds it to be useful.
An Explanation: The intent of this post is to produce an understandable explanation and outline of the natural reproduction process of mushrooms. Included with the text is a glossary which should define some of the difficult terminology.
A Quick Analogy: A spore is much like a seed. It contains all of the genetic information that will grow and produce the fruit of the mushroom. The mushroom is the sex organ of the mushroom that will produce spores or "seeds".
The Definition: A spore is a nearly microscopic, sometimes single-celled reproductive body that is extremely resistant to desiccation and heat and is capable of growing into a new organism, produced especially by certain bacteria, fungi, algae, and nonflowering plants.
Mycelial Reproduction: When spores germinate (reproduce) a thread emerges from the spore casing. When two threads from different spore bodies intersect, they attempt to mate through a hook and clamp connection. A tiny pipe is opened between threads and genetic material is exchanged. The genetically complete threads become hyphae and begin to grow.
Spores have four combinations of sexes. Not all intersecting threads are able to mate. Not all matings will produce fertile mycelia.
Spores form as swellings on one or more subtending hypha in the soil or in roots. These structures contain lipids, cytoplasm and many nuclei. Spores usually develop thick walls with more than one layer and can function as propagules. Spores may be aggregated into groups called sporocarps. Sporocarps may contain specialized hyphae and can be encased in an outer layer (peridium). Spores apparently form when nutrients are remobilised from roots where associations are senescing. They function as storage structures, resting stages and propagules. Spores may form specialized germination structures, or hyphae may emerge through the subtending hyphae or grow directly through the wall.
A single spore contains a half set of chromosomes (known as haploid), much like any reproductive cell (ova or sperm). The spore has a protein sheath (the colored part that we can see) which encases the cell. When optimal conditions surround the spore, it will germinate. This is when it pushes its cellular mass through the protein sheath (at the germ pore) by expansion from re-absorbed water. This mass is a fine filament called the monokaryote (aka: the primary mycelium). It still has a half set of chromosomes. This monokaryote grows (still a single cell with a single nucleus) until it finds a compatible monokaryote to mate with. It does this by touching and dissolving its cell wall while the mate does the same. They effectively just merge to become one cell with 2 nuclei.
A Related Quote: "Asymmetric genome shuffling involves a fusion between a dikaryotic protoplast and a monokaryotic protoplast. Because only the cytoplasm of the monokaryon is inherited by the progeny, and one of either of the haplotypes of the dikaryon migrates into the progeny, the monokaryon is called a"recipient" and the dikaryon is called a "donor." Accordingly, the resulting fused dikaryotic progenies are heterokaryotic, but their cytoplasm is of the recipient monokaryon." (Tan)
Though the clamp connection serves a different function.
This is where things get strange. After the mating, the resultant cell can now reproduce by mitosis, but the cell still has 2 nuclei, as mentioned. So, when it mitoses, the 2 nuclei split for a total of 4 nuclei, but still only 2 cells. Speed of growth is much greater in these dikaryotic mycelial threads, because they don't have to stretch a single cell over a long gap. They simply split into more cells to spread.
Clamp connections form between 2 dikaryotic mycelial masses. This is how one of those little fuzzy white patches (aka mycelium) mates with the other white patches. The dikaryotic mycelia "clamps" together. Thus, reproduction is complete.
Chromosome: A threadlike linear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information.
Cytoplasm: The protoplasm outside the nucleus of a cell.
Dikaryotic: Having two different and distinct nuclei per cell; found in the fungi. A dikaryotic individual is called a dikaryon.
Hyphae: Any of the threadlike filaments forming the mycelium of a fungus.
Lipids: Biological molecules soluble in apolar solvents.
Mitosis: The process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes. Also called karyokinesis. The entire process of cell division including division of the nucleus and the cytoplasm.
Monokaryote: A cell having only one haploid nucleus.
Mycelia: The vegetative part of a fungus, consisting of a mass of branching, threadlike hyphae.
Nuclei: A plural of nucleus. Biology. A large, membrane-bound, usually spherical protoplasmic structure within a living cell, containing the cell's hereditary material and controlling its metabolism, growth, and reproduction.
Peridium: The covering of the spore-bearing organ in many fungi.
Propagule: Any of various usually vegetative portions of a plant, such as a bud or other offshoot, that aid in dispersal of the species and from which a new individual may develop.
Sporocarps: A multicellular structure in which spores are formed, especially in red algae and certain fungi and slime molds. A receptacle containing sporangia, as in the pepperwort.
Sporulation: To produce or release spores.
Subtending: To be opposite to and delimit: The side of a triangle subtends the opposite angle.