Seminal fluid components alone stimulate post-mating changes in honey bee queens (Apis mellifera)

Honey bee queens undergo dramatic behavioral (e.g., reduced sexual receptivity), physiological (e.g., ovary activation, ovulation, and modulation of pheromone production) and molecular changes after they complete mating. To elucidate how queen post-mating changes are influenced by seminal fluid, a non-spermatozoa-containing component of semen, we injected queens with semen or seminal fluid alone. We assessed queen sexual receptivity, ovary development, worker retinue response (which is influenced by queen pheromone production), and transcriptional changes in queen abdominal fat body and brain tissues. Injection with either seminal fluid or semen resulted in decreased sexual receptivity, increased attractiveness of queens to workers, and altered expression of several genes that are also regulated in naturally mated queens. The post-mating and transcriptional changes of queens receiving seminal fluid were not significantly different from queens treated with seminal fluid, suggesting that components in seminal fluid, such as seminal fluid proteins, are largely responsible for stimulating post-mating changes in queens. 38 samples total were analyzed. These samples comprised 20 fat body RNAseq libraries and 18 brain RNAseq libraries from 20 queens. Queens were injected in the abdomen with Hayes solution (fat body n=5;brain n=5 ), semen (fat body n=5;brain n=5), or seminal fluid ((fat body n=5;brain n=3), or were not treated at all (controls, fat body n=5;brain n=5).