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Fungus farming ant genome reveals insight into adaptation of social behavior


June 30, 2011 – The development of agriculture was a significant event in human cultural evolution, but we are not the only organisms to have adopted an agricultural way of life. In a study published online today in Genome Research (www.genome.org),researchers have sequenced the genome of a fungus farming leaf-cutting ant, revealing new insights into the genetics and molecular biology behind this unusual lifestyle.

Found in Central and South America as well as the southern United States, leaf-cutting ants have evolved a symbiotic relationship with fungus. By breaking down leaves into mulch, the ants help the fungus to grow special structures for large societies of ants to feed upon.

The Panamanian leaf-cutting ant Acromyrmex echinatior farms fungus on leaf fragments for food. Minor workers tend the fungus garden and nurse the brood, major workers defend the colony and bring in new leaf fragments. 
The Panamanian leaf-cutting ant Acromyrmex echinatior farms fungus on leaf fragments for food. Minor workers tend the fungus garden and nurse the brood, major workers defend the colony and bring in new leaf fragments. Photo: David R. Nash ´┐Ż 2011.

Since being recognized as a new Panamanian species about 15 years ago, much has been learned about the biology of the leaf-cutting ant Acromyrmex echinatior, but the genetic basis of their farming lifestyle remained largely unknown. In this report, an international team of researchers has sequenced the genome of A. echinatior, and by comparison to other ant and insect genomes, identified genomic clues to the evolution of fungus farming behavior.

The authors noted that one of the most interesting findings in the genome of this leaf-cutting ant was that there are more genes in two particularly noteworthy gene families. "Based on their function in other organisms, we expect them to be involved in mating system adaptations and symbiotic food processing with the fungus," said Dr. Sanne Nygaard of the Copenhagen Centre for Social Evolution, co-lead author of the study.

Nygaard explained that these findings are especially fascinating because known evolutionary changes in the reproductive biology and farming lifestyle of these ants can now be linked to specific genomic features.

The authors also noted a particularly surprising result when comparing genes coding for neuropeptides, the small molecules that drive many biological processes, between the leaf-cutting ant and the sequenced genes of other ants with varied habitats, diets, and behaviors. They expected that differences in neuropeptide genes would be pronounced, but they found just the opposite.

"An identical set of neuropeptide genes is present in all the ant genomes we examined," said Nygaard, "showing that these genes are remarkably conserved." The authors suggest that the neuroendocrinology of all ants may have a very similar make-up, going back to the dawn of social evolution in the ancestor of all present ants.

"We are as yet only scratching the surface of the fascinating adaptations that will likely be revealed in the coming years," added Dr. Jacobus Boomsma, Director of the Copenhagen Centre for Social Evolution and co-senior author of the report, explaining that the genome sequence and analysis performed here will set the stage for further insights into the biology of social behavior.

Scientists from the University of Copenhagen (Copenhagen, Denmark), BGI-Shenzhen (Shenzhen, China), the University of Lausanne (Lausanne, Switzerland), and the Natural History Museum of Denmark (Copenhagen, Denmark) contributed to this study.

This work was supported by the Danish National Research Foundation, the Danish Research Agency, the Novo Nordisk Foundation, and the Swiss National Science Foundation.

Media contacts:
The authors are available for more information by contacting:
Dr. Sanne Nygaard, Centre for Social Evolution, University of Copenhagen:
[email protected] ; cell phone +45 30 95 59 01
Dr. Guojie Zhang, Scientific Department, BGI-Shenzhen:
[email protected] ; cell phone +86 134 2288 3247
Prof. Jacobus J. Boomsma, Centre for Social Evolution, University of Copenhagen:
[email protected] ; cell phone +45 20436771
Interested reporters may obtain copies of the manuscript
from Peggy Calicchia, Administrative Assistant, Genome Research
( [email protected] ; +1-516-422-4012 ).

About the article:
The manuscript will be published online ahead of print on Thursday, June 30, 2011. ´┐ŻIts full citation is as follows:
Nygaard S, Zhang G, Schi´┐Żtt M, Li C, Wurm Y, Hu H, Zhou J, Ji L, Qiu F, Rasmussen M, Pan H, Hauser F, Krogh A, Grimmelikhuijzen CJP, Wang J, Boomsma JJ. The genome of the leaf-cutting ant Acromyrmex echinatior suggests key adaptations to advanced social life and fungus farming. Genome Res doi: 10.1101/gr.121392.111.

About Genome Research:
Launched in 1995, Genome Research ( www.genome.org) is an international, continuously published, peer-reviewed journal that focuses on research that provides novel insights into the genome biology of all organisms, including advances in genomic medicine. ´┐ŻAmong the topics considered by the journal are genome structure and function, comparative genomics, molecular evolution, genome-scale quantitative and population genetics, proteomics, epigenomics, and systems biology. The journal also features exciting gene discoveries and reports of cutting-edge computational biology and high-throughput methodologies.
About Cold Spring Harbor Laboratory Press:
Cold Spring Harbor Laboratory is a private, nonprofit institution in New York that conducts research in cancer and other life sciences and has a variety of educational programs. Its Press, originating in 1933, is the largest of the Laboratory’s five education divisions and is a publisher of books, journals, and electronic media for scientists, students, and the general public.
Genome Research issues press releases to highlight significant research studies that are published in the journal.

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