A study of cellular proliferation and apoptosis in short- and long-lived honey bees, Apis mellifera.

摘要

Replicative senescence and apoptosis are two cellular processes that have been linked repeatedly to life expectancy in many organisms. However, aging research at the cellular level in the novel model Apis mellifera (honey bees) has been limited. This study tests the hypothesis that cellular proliferation will be higher and apoptosis will be lower in bees with high natural life expectancy (queens, reproductive workers and workers in the winter) than in bees with low life expectancy (drones, normal summer workers). The DeadEnd Colorimetric TUNEL assay was used to investigate apoptosis, but I observed no quantifiable results. A 5-bromo-2'-deoxyuridine (BrdU) incorporation assay was used to examine cellular proliferation in relation to age, caste, season, and reproductive status. I focused on the midgut because it was the only tissue that showed consistent cellular proliferation and is crucial for organismal survival. Cellular proliferation decreased significantly with age in summer workers and queens but it was highest in drones at an intermediate age. In winter workers, cellular proliferation was most similar to that of middle-aged summer workers, which is also true for their behavior and physiology. No direct link was found between reproduction and cellular proliferation in workers. These results suggest that there is no direct link between the amount of cellular proliferation in the midgut and honey bee longevity. Instead, the observed patterns in proliferation may reflect the variation in intestinal activity. I propose the new digestive demand hypothesis. However, the results do not exclude replicative senescence of the intestinal stem cells over time as an important determinant of honey bee life expectancy.