Arjuna Rajakumar

McGill University
The DNA damage response pathway reinforces social harmony in ant societies.

Arjuna Rajakumar, Jane Ding, Dr. Ehab Abouheif

A key feature of eusociality in ant colonies is their reproductive division of labor, where queens reproduce and workers perform most other tasks. However, in the majority of ant genera, workers have retained their ovaries creating a potential conflict between queens and workers over reproduction. In advanced ant societies, this conflict is reduced through an adaptive developmental mechanism called ‘Reproductive Constraint,’ which causes the mislocalization of mRNA’s and proteins that regulate germline and axis specification in worker ovaries. This mechanism results in ‘failed’ eggs reducing production of viable embryos. At the same time, Reproducive constraint facilitates production of trophic embryos for nutrition. Despite the importance of reproductive constraint in reducing conflict over reproduction and transforming ovaries into a food producing organ to feed the colony, little is known about its underlying molecular mechanism. Therefore, we examine the role of the DNA-damage response (DDR) pathway, a highly conserved pathway that regulates fertility, in regulating Reproductive Constraint in worker ovaries. We uncovered differential regulation of the DNA-damage response pathway between queens and worker ovaries, where workers show overall upregulation and sustained activation of DDR proteins throughout gametogenesis. Furthermore, we identified the DDR kinase Checkpoint kinase 2 (Chk2) as being almost exclusively active in worker ovaries and found that targeting its activity through a small-molecule Chk2 inhibitor is able to increase worker reproductive activity and potential, and partially rescue the effects of Reproductive Constraint. Overall, our findings suggest that the DNA-damage response pathway was coopted to regulate Reproductive Constraint in advanced ant societies.