Omphalotus olearius (The Jack O'Lantern Mushroom)



As humans, we are naturally driven to find a mate. Typically at the beginning of early adulthood, the search for a match begins. At the beginning of this search, a sign that you havyoung e met your match could be the connection you feel when he asks you to the camp dance. Another person may know it’s the one when their partner shares a common interest in chickens. Whatever it may be, we all have specific criteria for determining compatibility. Fungi use genetic codes instead of social cues in order to know when they have met their mate. While a love of chickens may be a standard for a human, a specific allele is a standard for a fungus. A mating type locus, sometimes simplified as MAT, is the gene that controls the mating identity for fungi. Omphalotus olearius undergoes a unique process called tetrapolar mating. The opposite of this process is bgillsipolar mating. Bipolar mating utilizes 1 locus, while tetrapolar mating utilizes 2 loci. In order for the two mating types to be sexually compatible during tetrapolar mating, the 2 strains need to have different alleles at both loci. The number of mating types varies with each organism that possesses this trait. Omphalotus olearius is known to have hundreds of mating types. (Ni et al. 2011) The purpose of having mating types is so that a fungi can determine sexually compatible mates, since they don’t have sexual differentiation. The advantage for having a large number of mating types is to increase chances of finding a compatible mate. Also, it creates genetic diversity in a population. Genetic diversity helps organisms to have a better chance of survival. For example, consider that there is a bacteria infecting mushrooms with a type A gene. If there are both type A genes and type B genes, then the type A gene will be affected while the type B gene will not. In contrast, if all of the mushrooms were simply type A, then the bacteria will affect them all. O. olearius has even shown to possess the skill to allow opposite mating types the ability to reproduce and mate when environmental stressors are present. (Ni et al. 2011)

Omphalotus olearius is a Basidiomycete meaning that its spores are produced externally on a basidium. In the picture to the right, you can observe the gills that are found on the underside of the mushrooms cap. On each gill there are many basidia clumped in abasidium collection called a basidiocarp. Figure 1 shows the structure of the basidium. The spores on a basidium are called basidiospores. You can notice that the spores are found on the outside of the structure, therefore are found externally. This is a defining characteristic of the Basidiomycota.

Another defining characteristic of the Basidiomycota is their clamp connections. As previously mentioned, Basidiomycetes use spores to reproduce. However, the fruiting body, the basidiocarp, is just what is seen above the surface. The basidiocarp is the mushroom structure that you see. It is not figure 2the growth form, and is only for reproduction and spore dispersal. Below the surface, the hyphae are working to decompose matter and expand. Hyphae are structures which excrete enzymes to break down material and allow the fungus to grow. Clamp connections are found on the hyphae of Basidiomycetes. Figure 2 shows the basic process of clamp connections. During this process, two nuclei undergo mitotic division. One of the daughter cells from each nuclei is taken by the clamp and the other progresses forward. The two remaining nuclei are separated by a septum. This process of clamp connections is necessary to create genetic diversity. Read more about this process on my Interactions with species page.

A collection of hyphae are formed into a mycelium. The mycelium is the growth form for the fungus. They are what produce the basidiocarps.  A process called karyogamy occurs in each basidium. This is when two nuclei fuse and produce a diploid nucleus. The diploid nucleus then undergoes meiosis and produces four haploid nuclei that develop into basidiospores. The spores are borne on the basidium until they reach maturity, and then are dispersed into nature by wind. The Jack O’Lantern Mushrooms cap is rounded down completely at immaturity. As the mushroom matures, the cap opens so that by the time it has reached full maturity, the gills are fully exposed. This is to create the best possible chance for the spores to disperse.

Take a look at the image below to see the entire life cycle drawn out. One thing to note is that Basidiomycota are independent of water, meaning that they don’t need water to reproduce. This is in comparison to Curly Leaf Pondweed which is water dependent.

 figure 3


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