title: The molecular correlates of organ loss: the case of insect Malpighian tubules.
abstract: Malpighian tubules play an essential role in excretion, osmoregulation and immunity of most insects. Exceptionally, aphids lack Malpighian tubules, providing the opportunity to investigate the fate of genes expressed in an organ that has undergone evolutionary reduction and loss. Making use of the sequenced genomes of Drosophila melanogaster and the pea aphid Acyrthosiphon pisum, we demonstrated that more than 50% of Drosophila genes expressed specifically in the Malpighian tubules had orthologues in the pea aphid genome and that most of the pea aphid orthologues with detectable expression were identified in the gut transcriptome. Relative to the whole genome, genes functioning in amino acid metabolism are significantly over-represented among the pea aphid orthologues of Malpighian tubule genes, likely reflecting the central importance of amino acid acquisition and metabolism in aphids. This study demonstrates that the evolutionary loss of a key insect organ, the Malpighian tubules, has not been associated with the coupled loss of molecular functions.
authors.affiliation: Department of Entomology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Jing
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: White
authors.affiliation: Department of Entomology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Entomology, Cornell University, Ithaca, NY 14853, USA Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA aes326@cornell.edu.
authors.forename: Angela E
authors.initials: AE
authors.lastname: Douglas
mesh_terms: D000818:Animals; D001042:Aphids / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D005075:Biological Evolution; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D019143:Evolution, Molecular; D015870:Gene Expression; D008317:Malpighian Tubules / Q000254:growth & development* / Q000378:metabolism
keywords: Acyrthosiphon pisum; Drosophila melanogaster; Malpighian tubules; gene orthologue; organ loss