title: Vitellogenin RNAi halts ovarian growth and diverts reproductive proteins and lipids in young grasshoppers.
abstract: Reduced reproduction extends lifespan of females in many animals. To test the effects of reproduction on storage of macronutrients, we block reproductive output in the lubber grasshopper by injecting RNAi against the precursor to egg-yolk protein, vitellogenin, in early adulthood. Controls were injected with either buffer or RNAi against the major storage protein in the hemolymph, hexamerin-90. Vitellogenin RNAi greatly reduced both levels of mRNA for vitellogenin and ovarian growth, in comparison to both controls. Fat body mass was increased upon vitellogenin RNAi, but concentrations of the three hexameric storage proteins from the hemolymph were not. Surprisingly, hemolymph vitellogenin levels were increased upon vitellogenin RNAi. Total reproductive protein (hemolymph vitellogenin plus ovarian vitellin) was unchanged by vitellogenin RNAi, as reproductive protein was diverted to the hemolymph. Similarly, the increased lipid storage upon vitellogenin RNAi was largely attributable to the reduction in lipid in the ovary, due to decreased ovarian growth. A BLAST search revealed that the 515 bp sequence of vitellogenin used for RNAi had three 11 bp regions identical to the vitellogenin receptor of the cockroach Leucophaea maderae. This suggests that our treatment, in addition to reducing levels of vitellogenin transcript, may have also blocked transport of vitellogenin from the hemolymph to the ovary. This would be consistent with halted ovarian growth simultaneous with high levels of vitellogenin in the hemolymph. Nonetheless, the accumulation of vitellogenin, instead of hexameric storage proteins, is inconsistent with a simple model of the trade-off between reproduction and storage. This was observed in young females; future studies will address whether investment of proteins may shift to the soma as individuals age. Overall, our results suggest that blockage of reproduction in young grasshoppers redirects lipids to storage and reproductive proteins to the hemolymph.
authors.affiliation: *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA.
authors.forename: Derek R
authors.initials: DR
authors.lastname: Tokar
authors.affiliation: *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Veleta
authors.affiliation: *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Canzano
authors.affiliation: *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hahn
authors.affiliation: *Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Entomology and Nematology, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611, USA jhatle@unf.edu.
authors.forename: John D
authors.initials: JD
authors.lastname: Hatle
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D005216:Fat Body / Q000254:growth & development / Q000378:metabolism; D005260:Female; D055785:Gene Knockdown Techniques; D006110:Grasshoppers / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D006458:Hemolymph / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D009758:Nymph / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D010053:Ovary / Q000254:growth & development / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014819:Vitellogenins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D019476:Insect Proteins; D012333:RNA, Messenger; D014819:Vitellogenins; C041137:storage proteins, Insecta