RNA-seq reveals disruption of gene regulation when honey bees are caged and deprived of hive conditions

Abstract

In this study, we present phenotypic and genetic data characterizing the impact of imidacloprid and caging stress on honey bee Apis mellifera physiological responses and regulation of 45 genes using targeted-RNA seq. The term 'caging stress' characterizes the effects of depriving honey bees of all hive aspects and conditions. Two cohorts of 1 day old sister bees were subjected to different conditions. One cohort was caged and fed different imidacloprid-tainted sugar solutions and the second was marked and introduced back to its natal hive. Physiological bee parameters and diet behavior were monitored daily for caged bees over several weeks. Bee samples from both cohorts were sampled weekly for RNA sequencing and oxidative stress analyses. Imidacloprid induced significant protein damage and post-ingestive aversion responses in caged bees, leading to lower tainted syrup consumption and higher water intake compared with the controls. No differentially expressed genes were observed among caged bees in regards to imidacloprid treatment. However, significant upregulation in antioxidant genes was recorded in caged bees as compared with hive bees, with overwhelming downregulation in all gene categories in caged bees at week 4. We identified two sets of genes that were constantly regulated in caged bees, including Rsod with unknown function in insects that could potentially characterize caging stress in honey bees.

Keywords: Cage stress; Gene regulation; Honey bee; Imidacloprid; Oxidative stress; RNA-seq.