title: Genotype effect on lifespan following vitellogenin knockdown.
abstract: Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely tied to behavioral maturation. Workers who initiate foraging behavior at earlier ages have shorter lifespans, and much of the variation in total lifespan can be explained by differences in pre-foraging lifespan. Vitellogenin (Vg), a yolk precursor protein, influences worker lifespan both as a regulator of behavioral maturation and through anti-oxidant and immune functions. Experimental reduction of Vg mRNA, and thus Vg protein levels, in wild-type bees results in precocious foraging behavior, decreased lifespan, and increased susceptibility to oxidative damage. We sought to separate the effects of Vg on lifespan due to behavioral maturation from those due to immune and antioxidant function using two selected strains of honey bees that differ in their phenotypic responsiveness to Vg gene knockdown. Surprisingly, we found that lifespans lengthen in the strain described as behaviorally and hormonally insensitive to Vg reduction. We then performed targeted gene expression analyses on genes hypothesized to mediate aging and lifespan: the insulin-like peptides (Ilp1 and 2) and manganese superoxide dismutase (mnSOD). The two honey bee Ilps are the most upstream components in the insulin-signaling pathway, which influences lifespan in Drosophila melanogaster and other organisms, while manganese superoxide dismutase encodes an enzyme with antioxidant functions in animals. We found expression differences in the llps in fat body related to behavior (llp1 and 2) and genetic background (Ilp2), but did not find strain by treatment effects. Expression of mnSOD was also affected by behavior and genetic background. Additionally, we observed a differential response to Vg knockdown in fat body expression of mnSOD, suggesting that antioxidant pathways may partially explain the strain-specific lifespan responses to Vg knockdown.
authors.affiliation: Arizona State University, School of Life Sciences, Tempe, AZ 85287, USA; Smithsonian Tropical Research Institute, Panama City, Panama, Apartado Postal 0843-03092, Panama. Electronic address: kateihle@gmail.com.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Ihle
authors.affiliation: Arizona State University, School of Life Sciences, Tempe, AZ 85287, USA; University of California, Davis, Department of Entomology and Nematology, Shields Avenue, Davis, CA 95616-5270, USA. Electronic address: mkfondrk@ucdavis.edu.
authors.forename: M Kim
authors.initials: MK
authors.lastname: Fondrk
authors.affiliation: Arizona State University, School of Life Sciences, Tempe, AZ 85287, USA. Electronic address: Robert.Page@asu.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Page
authors.affiliation: Arizona State University, School of Life Sciences, Tempe, AZ 85287, USA; Norwegian University of Life Sciences, Department of Chemistry, Biotechnology and Food Science, Aas 1432, Norway. Electronic address: Gro.Amdam@asu.edu.
authors.forename: Gro V
authors.initials: GV
authors.lastname: Amdam
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001516:Bees / Q000502:physiology*; D001921:Brain / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005838:Genotype; D019476:Insect Proteins / Q000502:physiology; D008136:Longevity; D013045:Species Specificity; D013482:Superoxide Dismutase / Q000502:physiology; D014819:Vitellogenins / Q000235:genetics / Q000502:physiology*
chemical_list: D019476:Insect Proteins; D014819:Vitellogenins; D013482:Superoxide Dismutase
keywords: Apis mellifera; Foraging; Longevity; RNA-interference; Vitellogenin