[correction: When the genome paper first emerged I stated that the genomes would not be made public. This impression- due to a lag time between online publication and data release- was erroneous, and I hope the authors accept my apology.]
A few days have passed since the publication by Bonasio et al of the first ant genomes, those of the Florida Carpenter ant Camponotus floridanus and the Indian jumping ant Harpegnathos saltator. After reading over the paper and the supplemental information, here are my thoughts.
- Although the paper is initially framed as a comparison between the two species, that aspect of the research is not as informative as you might think.
The temptation to contrast a socially “primitive” with an “advanced” ant is strong, but ultimately the two species differ in so many other respects that such comparisons are premature. For example, Harpegnathos is more visually oriented. Camponotus is trophically intertwined with a gut endosymbiont. Harpegnathos nests in soil; Camponotus in rotting wood. These and other other trait differences cloud our ability to make sense of which genomic features track the social organization and which are involved in other aspects of the ants’ biology. This is not a flaw of the research- the authors explicitly mention this limitation- but just a note of caution against reading too much into the initial contrasts.
- While the inter-species comparisons are perhaps not so useful (yet!), the inter-caste comparisons within species are fascinating. What makes this a high-value Science paper rather than a lesser effort is that the authors did not just describe the genome. Rather, they used it as a tool to test hypotheses about how gene activity differs between queens and workers.
Here’s one example. Ant reproductives can be extraordinarily long-lived animals. Some laboratory queens have survived more than 30 years. That, I’m guessing, is older than some of my readers. Yet workers of the same species burn through their lives in just a fraction of the time. A few months, or maybe a couple years.
It has long been thought for most animals that degradation of the repetitive ends of chromosomes- the telomeres- is related to cell aging. A cell with tattered telomores isn’t long for the world. So we might expect that reproductives and workers have differ in the regulation of enzymes that maintain the telomeres. And sure enough, when Bonasio et al compared the levels of telomerase activity in Harpegnathos they found that gamergates (workers that have become reproductive) showed a much higher level than workers. These genomes are helping to show- at a molecular level- how it is that some individuals live longer.
- As is too often the case with articles appearing in the high-impact journals, some of the most interesting bits are relegated to the supplemental material. Among the banished treasures are bits on bacterial endosymbionts (the team recovered nearly the entire Blochmannia genome out of the Camponotus and they discovered an unexpected Rhizobiales in the Harpegnathos), and sex determination (neither ant apparently uses the csd locus from the other completed eusocial genome, the honey bee). The selection of what made the primary paper and what was cut appears to reflect the medical focus of the PIs and the funding source rather that what we ant bloggers like to think of as important.
- Back in ancient genomics history, two or maybe even three years ago, a eukaryotic genome couldn’t be published without 100 authors in a massive international collaboration. Bonasio et al, with a scant 16 authors, is a tribute to how far genomics has advanced. At this rate of technology streamlining, masters students will be single-authoring genomes within a decade.
These are the first two ant genomes, but more are on the way. The end of the year should see publication of the genomes of four additional ants, including a leafcutter ant, a fire ant, the Argentine ant, and a harvester ant. When pooled, we should have a sample size large enough to draw significant comparative conclusions. Regardless, the Bonasio et al paper is a strong opening salvo to the new era of ant genomics.
source: Roberto Bonasio, Guojie Zhang, Chaoyang Ye, Navdeep S. Mutti, Xiaodong Fang, Nan Qin, Greg Donahue, Pengcheng Yang, Qiye Li, Cai Li, Pei Zhang, Zhiyong Huang, Shelley L. Berger, Danny Reinberg, Jun Wang, and Jürgen Liebig. Genomic Comparison of the Ants Camponotus floridanus and Harpegnathos saltator. Science, 2010: 329 (5995): 1068-1071 DOI: 10.1126/science.1192428