Some bioluminescent fungi that grow on the arctic tundra have been found to have the largest fungal genomes known to science.
These mushrooms show widespread growth across their genome. This includes not only the genes that help them invade or interact with plants and break down carbon, but also genes whose functions are not yet known but are likely important.
The boffins are assuredly excited by these findings - no doubt more info will be forthcoming as they uncover the secrets of the big genomes.