Today's Picture comes from ScienceDaily.comFungi, Basidiomycota, Agaricomycetes, Hymenomycetes, Agaricales, Hydnangiaceae, Laccaria, L. bicolor
Laccaria bicolor is a common and cosmopolitan fungi that is best known for its ability to form a type of symbiotic relationship with plants known as an ectomycorrhizal associations. This type of partnership is characterized by the fine hyphal sheath the fungus grows around root tips of woody plants, some times referred to as a Hartig net. This complex network of hyphae allows the fungus to absorb nutrients (generally nitrogen and phosphorus) from the surrounding soil, and exchanges it with the host plant. Ectomycorrhizal (EM) fungi can be contrasted with Arbuscularmycorrizal (AM) fungi, whose hyphae actually penetrate into the root cells instead of just the intracellular space. In return for environmental nutrients, the fungi have improved access to carbon sources of the plant, which can sometimes produce a carbohydrate rich exudate to encourage fungal colonization.
Ectomycorrizal associations are found in about 10% of all plants, with L. bicolor most often found associated with birch, fir, pine, and poplar trees. One of the most amazing things about L. bicolor is that is has been found to release a toxin to hunt, immobilize, and kill springtails, a small invertebrate in the collembola subclass of arthropods. Investigators were able to show that L. bicolor was able to procure up to 25% of its total nitrogen intake from these soil arthropods. This finding could have significant impacts on the way ecologists understand the flow of carbon and nitrogen through these ecosystems.
L. bicolor was also the first symbiotic fungi to be sequenced and has one of the largest fungal genomes to date, with over 65 million nucleotides (65Mb) coding over 20,000 proteins. By comparison, the human genome has around 3 billion nucleotides but only around 20,000-25,000 genes. It is of specific interest to me, because I'm interested in they types of ecological factors influence genome size and gene family expansion/contraction. L. bicolor represents an opportunity to test some of the hypotheses I've had rolling around the back of my head.
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