Effects of commercial queen rearing methods on queen fecundity and genome methylation

The queen and worker castes of the honey bee are very distinct phenotypes that result from different epigenomically regulated developmental programs. In commercial queen rearing, it is common to produce queens by transplanting worker larvae to queen cells to be raised as queens. Here, we examined the consequences of this practice for queen ovary development and genome-wide methylation. Queens reared from transplanted older worker larvae weighed less and had fewer ovarioles than queens reared from transplanted eggs. Methylome analyses revealed a large number of genomic regions in comparisons of egg reared and larvae reared queens. The methylation differences became more pronounced as the age of the transplanted larva increased. Differentially methylated genes had functions in reproduction, longevity, immunity, and metabolic functions suggesting that the methylome of larval reared queens was compromised and more worker-like than the methylome of queens reared from eggs. These findings caution that queens reared from worker larvae are likely less fecund and less healthy than queens reared from transplanted eggs.