title: Large-scale label-free quantitative proteomics of the pea aphid-Buchnera symbiosis.
abstract: Many insects are nutritionally dependent on symbiotic microorganisms that have tiny genomes and are housed in specialized host cells called bacteriocytes. The obligate symbiosis between the pea aphid Acyrthosiphon pisum and the γ-proteobacterium Buchnera aphidicola (only 584 predicted proteins) is particularly amenable for molecular analysis because the genomes of both partners have been sequenced. To better define the symbiotic relationship between this aphid and Buchnera, we used large-scale, high accuracy tandem mass spectrometry (nanoLC-LTQ-Orbtrap) to identify aphid and Buchnera proteins in the whole aphid body, purified bacteriocytes, isolated Buchnera cells and the residual bacteriocyte fraction. More than 1900 aphid and 400 Buchnera proteins were identified. All enzymes in amino acid metabolism annotated in the Buchnera genome were detected, reflecting the high (68%) coverage of the proteome and supporting the core function of Buchnera in the aphid symbiosis. Transporters mediating the transport of predicted metabolites were present in the bacteriocyte. Label-free spectral counting combined with hierarchical clustering, allowed to define the quantitative distribution of a subset of these proteins across both symbiotic partners, yielding no evidence for the selective transfer of protein among the partners in either direction. This is the first quantitative proteome analysis of bacteriocyte symbiosis, providing a wealth of information about molecular function of both the host cell and bacterial symbiont.
authors.affiliation: Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Anton
authors.initials: A
authors.lastname: Poliakov
authors.forename: Calum W
authors.initials: CW
authors.lastname: Russell
authors.forename: Lalit
authors.initials: L
authors.lastname: Ponnala
authors.forename: Harold J
authors.initials: HJ
authors.lastname: Hoops
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.forename: Angela E
authors.initials: AE
authors.lastname: Douglas
authors.forename: Klaas J
authors.initials: KJ
authors.lastname: van Wijk
mesh_terms: D000465:Algorithms; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001042:Aphids / Q000201:enzymology / Q000378:metabolism* / Q000382:microbiology; D001426:Bacterial Proteins / Q000378:metabolism*; D020635:Buchnera / Q000201:enzymology / Q000378:metabolism*; D002458:Cell Fractionation; D018834:Chaperonin 60 / Q000378:metabolism; D016000:Cluster Analysis; D005943:Gluconeogenesis; D019476:Insect Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D018532:Pisum sativum; D020543:Proteome / Q000378:metabolism*; D011687:Purines / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013559:Symbiosis; D053719:Tandem Mass Spectrometry
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D018834:Chaperonin 60; D019476:Insect Proteins; D026901:Membrane Transport Proteins; D020543:Proteome; D011687:Purines