GSE184993
How experimental competition changes ovarian gene activity in free living birds: implications for steroidogenesis, maternal effects, and beyond
The ovary plays an important role in mediating both a female's response to her own social environment and communicating it to her developing offspring. However, we know little about the underlying genomic mechanisms that facilitate social responsiveness in the ovary. This issue is further complicated by mixed support linking female competition to ovarian production of testosterone, the often-evoked mechanism mediating both social aggression and maternal effects. Here, we experimentally generated social competition among wild, cavity-nesting female birds (tree swallows, Tachycineta bicolor). After territorial settlement, we reduced the availability of key breeding resources (i.e., nest boxes), generating heightened competition; within 24hr we reversed the manipulation, causing aggressive interactions to subside. We measured transcriptomic responses in the ovary during the peak of competition and 48hr after it ended, along with date-matched controls. Network analyses indicated that competing females experienced an immediate and temporary decrease in the expression of genes involved in the early stages of steroidogenesis; however, two days after competition had ended, there was a marked increase in the expression of genes involved in the final stages of sex steroid biosynthesis, including HSD17B1. In addition, ovaries that had been socially primed also displayed altered activity in gene networks related to the cell cycle, muscle performance, and extracellular matrix organization, which collectively point to social effects on future reproduction. Altogether, these findings show how the social environment shapes ovarian processes associated with both social behavior and adaptive transgenerational plasticity. Overall design: ovaries were collected from 20 female tree swallows during peak competition (Day 0; n=6 experimental and n=5 controls) and two days after (Day 2; n=4 experimental and n=5 controls); total RNA was extracted and run on a Nextseq platform.