Interplay between Selenium, Selenoprotein genes and oxidative stress in honey bee Apis mellifera L

Authors: ALBURAKI, MOHAMED - University Of Southern Mississippi; SMITH, KRISTINA - University Of Southern Mississippi; Adamczyk, John; KARIM, SHAHID - University Of Southern Mississippi

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2019
Publication Date: 6/7/2019
Citation: Alburaki, M., Smith, K., Adamczyk Jr, J.J., Karim, S. 2019. Interplay between Selenium, Selenoprotein genes and oxidative stress in honey bee Apis mellifera L. Journal of Insect Physiology. https://doi.org/10.1016/j.jinsphys.2019.103891.
DOI: https://doi.org/10.1016/j.jinsphys.2019.103891

Interpretive Summary: The honey bee, Apis mellifera L., is a major pollinator insect that lacks ways to reduce harmful levels of Selenium (Se) naturally occurring in the environment. We investigated the effects of two inorganic forms of Se on biological traits, oxidative stress, and gene regulation. Using bioassay arenas in the laboratory, bees were fed 4 different concentrations of selenate and selenite, two common inorganic forms of Se. The levels of four honey bee antioxidant genes were evaluated, and three selenoprotein-like genes (SELENOT, SELENOK, SELENOF) were characterized as well as Sbp2; a selenium binding protein required for the translation of selenoproteins mRNA. Oxidative stress and Se residues were subsequently quantified in honey bee bodies throughout the experiment. Se induced higher oxidative stress in treated honey bees lead to significantly elevated protein carbonyl content, particularly at the highest studied concentrations. Early upregulations of Spb2 and MsrA were identified while all genes except SELENOT were upregulated substantially to alleviate the Se-induced oxidative stress levels.

Technical Abstract: The honey bee, Apis mellifera L., is a major pollinator insect that lacks novel selenoproteins genes rendering it susceptible to elevated levels of Selenium (Se) naturally occurring in the environment. We investigated the effects of two inorganic forms of Se on biological traits, oxidative stress, and gene regulation. Using bioassay arenas in the laboratory, sister bees that were 1-d old were fed ad libitum 4 different concentrations of selenate and selenite, two common inorganic forms of Se. The transcription levels of four honey bee antioxidant genes were evaluated, and three putative selenoprotein-like genes (SELENOT, SELENOK, SELENOF) were characterized as well as Sbp2; a selenium binding protein required for the translation of selenoproteins mRNA. Oxidative stress and Se residues were subsequently quantified in honey bee bodies throughout the experiment. Se induced higher oxidative stress in treated honey bees lead to significantly elevated protein carbonyl content, particularly at the highest studied concentrations. Early upregulations of Spb2 and MsrA were identified at day 2 of the treatment while all genes except SELENOT were upregulated substantially at day 8 to alleviate the Se-induced oxidative stress levels. We determined doses between 60-600 mg.Se.L-1 were acutely toxic to bees (<48h) while doses between 0.6-6 mg.Se.L-1 led to much lower morality (7 - 16)%. Furthermore, when fed ad libitum, Se residue data indicated that bees tolerated accumulation up to 0.12 µg Se bee-1 for at least 8 days with a Se LC50 of ~6 mg/L, a field realistic concentration found in pollen of certain plants in a high Se soil environment.