title: Testes-specific hemoglobins in Drosophila evolved by a combination of sub- and neofunctionalization after gene duplication.
abstract: BACKGROUND
  For a long time the presence of respiratory proteins in most insects has been considered unnecessary. However, in recent years it has become evident that globins belong to the standard repertoire of the insect genome. Like most other insect globins, the glob1 gene of Drosophila melanogaster displays a conserved expression pattern in the tracheae, the fat body and the Malpighian tubules.
  
  
  RESULTS
  Here we show that the recently discovered D. melanogaster globin genes glob2 and glob3 both display an unusual male-specific expression in the reproductive tract during spermatogenesis. Both paralogs are transcribed at equivalent mRNA levels and largely overlap in their cellular expression patterns during spermatogenesis. Phylogenetic analyses showed that glob2 and glob3 reflect a gene duplication event that occurred in the ancestor of the Sophophora subgenus at least 40 million years ago. Therefore, flies of the Drosophila subgenus harbor only one glob2/3-like gene.
  
  
  CONCLUSIONS
  Phylogenetic and sequence analyses indicate an evolution of the glob2 and glob3 duplicates by a combination of sub- and neofunctionalization. Considering their restricted, testes-specific expression, an involvement of both globins in alleviating oxidative stress during spermatogenesis is conceivable.
authors.affiliation: Institute of Molecular Genetics, University of Mainz, 55099 Mainz, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Gleixner
authors.forename: Holger
authors.initials: H
authors.lastname: Herlyn
authors.forename: Stefan
authors.initials: S
authors.lastname: Zimmerling
authors.forename: Thorsten
authors.initials: T
authors.lastname: Burmester
authors.forename: Thomas
authors.initials: T
authors.lastname: Hankeln
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental; D006454:Hemoglobins / Q000235:genetics*; D000860:Hypoxia / Q000235:genetics; D008297:Male; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA; D013091:Spermatogenesis / Q000235:genetics; D013737:Testis / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; C508898:Glob2 protein, Drosophila; C508899:Glob3 protein, Drosophila; D006454:Hemoglobins; D012333:RNA, Messenger