Abstract
Simple SummaryHoney bees play a critical role in agriculture as they provide pollination services to many agricultural crops. However, honey bee populations continue to decline due to exposure to pesticides, habitat destruction, pests, diseases and beekeeping practices. In this study, we assessed selected biological parameters associated with honey bee health in two beekeeping practices (organic and conventional). We compared total protein content in young worker bees from organically and conventionally managed apiaries. We also assessed differential gene expression at two levels of Varroa mite infestations (0% and 5%) in selected genes involved in nutrition and cellular defense (vitellogenin (Vg), malvolio (Mvl), prophenoloxidase (PPO)-, genes involved in lifespan (superoxide dismutase (Sod 1), superoxide dismutase 2 (Sod2)) and immune function genes (immune deficiency (Imd), spaetzle (Spz). Total soluble protein in young adult worker bees was similar in both beekeeping practices. The genes PPO, Vg and Mvl were upregulated in young adult bees with no mite infestations from organically managed apiaries and could mount an immune response through Spz and Sod 1 when challenged by 5% Varroa mite infestation levels. Overall, these findings provide useful insights into the genetic response of honey bees under two beekeeping practices and could help improve honey bee health.Honey bees are of great economic importance, not only for honey production but also for crop pollination. However, honey bee populations continue to decline mainly due to exposure to pesticides, pathogens and beekeeping practices. In this study, total soluble protein was measured, total RNA was extracted and first-strand cDNAs were generated. Quantitative PCR was used to assess the relative expression (transcript abundances) of immune function-related genes in honey bees collected from organically and conventionally managed hives. Honey bees collected from conventionally managed hives with 0% Varroa mite infestation levels displayed an upregulated expression of the prophenoloxidase gene (cellular defense). Similarly, honey bees collected from organically managed hives had increased levels of the vitellogenin gene (immune function and longevity). The gene expression for malvolio (sucrose responsiveness) was highest in organically managed hives with 0% Varroa mite infestations. Young adult bees collected from organically managed hives with 5% Varroa mite infestation levels had upregulated expressions of the gene spaetzle, whereas bees from similarly infested, conventionally managed hives did not, suggesting that honey bees from organically managed hives could mount an immune response. In young adult bees collected from organically managed hives only, the expression of the immune deficiency gene (antimicrobial defense) was upregulated. The relative gene expression for superoxide dismutase 1 increased in young adult bees collected from hives with 5% Varroa mite infestation levels as expected. However, for superoxide dismutase 2, there was a high level of gene expression in adult bees from both conventionally managed hives with 0% Varroa mite infestation levels and organically managed hives with 5% Varroa mite infestations. The gene CYP9Q3 (pesticide detoxification) that metabolizes coumaphos and fluvalinate was upregulated in adult bees collected from organically managed bees. Overall, these findings provide useful insights into the genetic response of honey bees to some environmental stressors and could be an important component of best beekeeping practices that intend to enhance honey bee health.
Highlights
The availability of environmental nutrients is an important determining factor of an organism’s growth and survival; malnutrition can impair immune function and affect animal health, resistance to diseases and survival [1]
We established two subsets of five colonies with 0% and 5% levels of Varroa mite infestations. These levels of mite infestations were chosen as reference points because, in previous studies, we found that most honey bee colonies with 5–10% Varroa mite infestations at the start of field trials perished before the end of the 42-day experimental period [14]
We showed that some selected genes linked to honey bee health can be affected by RNA between adult bees collected from organically and conventionally managed hives
Summary
The availability of environmental nutrients is an important determining factor of an organism’s growth and survival; malnutrition can impair immune function and affect animal health, resistance to diseases and survival [1]. Pollen and nectar are essential dietary sources for honey bees [2]. Amino acids, lipids, vitamins and minerals, all of which are vital for individual honey bee health and colony growth and development [1,2]. In the form of honey, is the carbohydrate source that provides the honey bee with energy [3]. Honey bees forage on a diversity of plants in order to receive adequate nutrition [1]. With the frequent placement of hives on monocultures, honey bees are faced with nutritional deficiencies affecting physiological development, immunocompetence (the ability to mount an immune response), or increased pesticide sensitivity [1,4]
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