What's Killing the Buzz? The Effects of Neonicotinoids on Apis mellifera Mitochondrial Metabolism

Abstract

Honeybees, Apis mellifera, are crucial pollinators in our world today. Approximately one third of the world's agriculture depends upon pollination by insects to increase crop yields. During their flights, which can cover up to five miles, bee flight muscles oxidize carbohydrates to produce ATP, through the processes of glycolysis in the cytoplasm and Krebs cycle/oxidative phosphorylation in the mitochondria. To transport pyruvate, the product of glycolysis, from the cytoplasm through the inner mitochondrial membrane, a transporter protein known as the mitochondrial pyruvate carrier (MPC), is required. If this transporter protein is inhibited, honeybees can't produce adequate energy for flight. One way this transporter could be impaired is by a class of pesticides called neonicotinoids, particularly Imidacloprid. This pesticide is the biggest concern to the honeybee because it is used on about 95% of corn and canola crops, and many fruits and vegetables. The seeds are coated in the pesticide, and it is assimilated and incorporated into the pollen and nectar which is consumed by the bees. Previous studies have shown that neonicotinoids affect the mitochondria by depolarizing the inner mitochondrial membrane potential which disrupts the proton gradient necessary for chemiosmosis. This could potentially have other effects within the mitochondria during the process of cellular respiration. In our experiment, we are testing the potential effects of Imidacloprid on the mitochondrial function of honeybees by examining rates of respiration and the expression levels of the MPC gene. We hypothesize that honeybees will up‐regulate the MPC as a response to the pesticide in order to increase their respiration rates and maintain ATP production. To test our hypothesis, we fed bees sugar solutions containing Imidacloprid (25ppb) and a control group. After 4 days of exposure RNA was extracted and converted to cDNA for quantitative PCR for control and 25ppb treatments. The qPCR results will allow us to determine the level of MPC gene expression within the control and exposed bees which we can then compare to determine if the gene was up‐ or down‐regulated. Mitochondria isolated from each group were tested in vitro using an Oxygraphplus to examine potential effects of Imidacloprid on respiration rates. Mitochondrial respiration rates for state 4 in our control and exposed honeybees were similar, 58.9nmol O2/min*mg protein, control, and 56.93nmol O2/min*mg protein, exposed. In our state 3 respiration our exposed honeybees had a higher rate, 104.94nmol O2/min*mg protein, as compared to our control group, 92.4nmol O2/min*mg protein. No statistical difference was observed between the control and exposed honeybees state 3, p=0.22, or state 4, p=0.26, respiration rates. We are currently running qPCR to test for changes in MPC gene expression in response to Imidacloprid exposure.Support or Funding InformationWe would like to thank Henson School of Science and Technology and Salisbury University's Green Fund for all of their support and funding through out this project.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.