III. Pollen Projects:
Pollen is a critical nutrient source for bees, serving as the primary source for protein, lipids, vitamins, and minerals. Reduced pollen quantity and diversity are both seen as critical contributors to nutritional stress experienced by bees. While engaged in the work described in sections I, II, and III, undergraduates in my lab have completed a number of projects providing new information about the biology of this key nutrition source. First, the Snow lab has produced two primary research papers and two reviews focused on the uptake of diet-derived miRNA by honey bees. Our results demonstrate that pollen-derived miRNAs are not efficiently taken up by the digestive tract or dispersed to distal tissues in honey bees. These results have implications for uptake in the context of the normal ecology of the bee and for understanding potential in the setting of genetically engineered organisms. Second, the mechanisms by which pollen is digested by honey bees are incompletely understood. We found that pollen collected by honey bees produce Reactive Oxygen Species (ROS) at robust levels upon germination, and pollen-localized ROS can be readily found in the digestive tract of honey bees. Our data provide evidence of retained metabolic activity in bee-collected pollen that lends support to pseudogermination, or the regulated partial germination of pollen, as an important mechanism for pollen digestion. In addition, they point to novel approaches for better understanding of pollen digestion in this species and beyond . Finally, in our examination of pollen from foraging bees, we observed the presence of thrips on pollen loads taken directly from the corbiculae of collecting forager bees over two summers. The observation of thrips on honey bee-collected pollen suggested that thrips could be transported by honey bee and that this may represent an example of phoresy (where one organism, the phoront, moves by attaching itself to a host organism). Based on these results, we proposed that thrips might be able to utilize honey bee-mediated transport for dispersal to distant plants, but additional study will be required to characterize this phenomenon more fully.