The Planet's Oldest Farmers: Sequencing the Genome of Ant-Grown Fungi.
Human civilization turned to agriculture around 10,000 years ago; however, farming had already been invented millions of years prior to this point. Ants in the group Attini evolved to cultivate fungus for their consumption around 60 million years ago. These remarkable insects collect plant matter to help their fungus farms grow and depend on these farms for their survival.
Researchers sequenced the genome of one species of cultivated fungus (Leucoagaricus gongylophorus) to see if domestication had caused changes in its DNA. In human-grown crops, there are some clear changes with domestication, such as polyploidy1, increased nutritional value, and reduced genetic diversity. It was expected that similar changes would be observed in the genomes of these ant-grown fungi.
These new findings revealed that these fungi carried genes involved in the production of new metabolites that could be useful for their relationship with ants. For example, the researchers predicted that some of these new metabolites could be antimicrobial or help enhance iron uptake in ants2.
These changes in the genome were driven by an increase in transposable elements. Transposable elements are segments of the genome that can move to a new location, acting as drivers of evolution. Around two-thirds of the fungus's genome was composed of transposable elements! This was much higher than in other fungi and was likely the cause of the massive changes in the genome associated with domestication2.
Ants with fungi farms are an incredible example of the diversity of animal behaviors out there. Further research on the specific new metabolites and genes in the fungi will tell us more about how the two species have coevolved. Finding hints of a mutualistic relationship in a fungus's genome makes me wonder what other evolutionary signatures we could find if we keep exploring the genomes of other species.
Polyploidy refers to a condition where a cell carries more than two copies of the genome. This increase in genetic material can give crops better adaptability to changing environments or cultivation practices↩
Leal-Dutra, C. A., Vizueta, J., Baril, T., Kooij, P. W., Rødsgaard-Jørgensen, A., Conlon, B. H., Croll, D., & Shik, J. Z. (2024). Genomic Signatures of Domestication in a Fungus Obligately Farmed by Leafcutter Ants. Molecular Biology and Evolution, 41(10)↩