Reporting on the sequencing of the first two ant genomes, scientists say their work can help them understand variations in appearance, biology and social roles within colonies as well as differences between ant species. The research, they say, could also clear a path to better understanding genes’ effects on social behavior, neurobiology and life-span in other animals.
“This study opens doors for a completely new system where now we can study behavior among ants and social insects,” says study coauthor Danny Reinberg, a biochemist at the New York University School of Medicine. The research appears in the Aug. 27 Science.
Ants live in colonies with queens and specialized workers of various types, each of which has a different set of biological and behavioral traits. Queens are larger than worker ants, can live 10 years or more and lay eggs all their lives. Shorter-lived workers have more complex behaviors and use more brainpower to forage and maintain the colony.
But all the individuals in a colony have the same genetic blueprints. That means differences among individuals depend on how genes are turned on and off, or cranked up or down, rather than the actual DNA. So scientists want to use ants to study how differences in genes and gene activity bring about changes in aging, behavior and brain activity.
The researchers, from institutions in the United States and China, chose two socially different ant species to sequence so that they could study a variety of ant lifestyles and behaviors. The Florida carpenter ant, Camponotus floridanus, lives in large colonies with one egg-laying queen that is crucial to the colony’s survival. Workers come in two sizes, have specialized tasks, and use smell to recognize each other and tell their peers where to find food.
In contrast, the jumping ant Harpegnathos saltator, from India, lives in smaller colonies that can replace a queen if she dies. Workers aren’t as highly specialized as carpenter ant workers and don’t recognize each other as easily.
Now that both genomes are sequenced, the scientists will start studying the differences among individuals and between species to find out whether ants’ actions, brain activity and life-span can be linked to gene activity. The researchers have already found some tantalizing tidbits that they’ll study further.
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Within jumping ants, the team found major gene-expression differences among colony members. For instance, worker ants that stepped up to replace a dead queen showed boosted levels of two antiaging enzymes, which may relate to queens’ longer lifespans. The researchers will study how the activity of these genes gets cranked up and how the genes affect aging.
Among the carpenter ants, the two types of workers had different gene-expression levels affecting brain function. Minor workers go out and find food, while major workers stay behind to defend the nest. Minor workers showed higher gene expression for some brain signaling molecules, possibly because these workers need more brainpower to find food, lay chemical trails to lead others, and find the nest again, says geneticist Roberto Bonasio of NYU School of Medicine, a coauthor of the study. The finding suggests workers’ different behaviors arise from differences in genes controlling brain signaling.
The researchers are just beginning to learn how gene activity modifies neurobiology in social insects.
“These kinds of things give clues to what kind of inputs are important for these species …to see how they control developmental strategies, social behavior, social responses,” says developmental biologist Vincenzo Pirrotta of Rutgers University in Piscataway, N.J., who was not involved in the research. “Particularly interesting is the pattern of development that can lead to such different body size and shapes as the body of a queen, for example.” While significant findings will come down the road, he sees this project as a great beginning.
In the future, Reinberg, Bonasio and colleagues plan to study the details of how environmental changes affect gene expression in these ants.
“This study is a beginning of what we want to do,” says Reinberg.