Mitochondrial capacity, oxidative damage and hypoxia gene expression are associated with age-related division of labor in honey bee, Apis mellifera L., workers

Abstract

During adult life, honeybee workers undergo a succession of behavioral states. Nurses bees perform tasks inside the nest, and when they are about 2-3 weeks old they initiate foraging. This switch is associated with alterations in diet, and with the levels of juvenile hormone and vitellogenin circulating in hemolymph. Less clear is whether this behavioral maturation involves major changes at the cellular level, such as mitochondrial activity and the redox environment in the head, thorax and abdomen. Using high-resolution respirometry, biochemical assays and RT-qPCR, we evaluated the association of these parameters with this behavioral change. We found that tissues from the head and abdomen of nurses have a higher OXPHOS capacity than those of foragers, while for the thorax we found an opposite situation. Since higher mitochondrial activity tends to generate more H2O2 and H2O2 is known to stabilize HIF-1α, this would be expected to stimulate hypoxia signaling. The positive correlation that we observed between mitochondrial activity and hif-1α gene expression in abdomen and head tissue of nurses would be in line with this hypothesis. Higher expression of antioxidant enzyme genes was observed in foragers, which could explain their low levels of protein carbonylation. No alterations were seen in NO levels, suggesting that NO signaling is unlikely to be involved in behavioral maturation. We conclude that the behavioral change seen in honeybee workers is reflected in differential mitochondrial activities and redox parameters, and we consider that this can provide insights into the underlying aging process.