title: Expansion of genes encoding piRNA-associated argonaute proteins in the pea aphid: diversification of expression profiles in different plastic morphs.
abstract: Piwi-interacting RNAs (piRNAs) are known to regulate transposon activity in germ cells of several animal models that propagate sexually. However, the role of piRNAs during asexual reproduction remains almost unknown. Aphids that can alternate sexual and asexual reproduction cycles in response to seasonal changes of photoperiod provide a unique opportunity to study piRNAs and the piRNA pathway in both reproductive modes. Taking advantage of the recently sequenced genome of the pea aphid Acyrthosiphon pisum, we found an unusually large lineage-specific expansion of genes encoding the Piwi sub-clade of Argonaute proteins. In situ hybridisation showed differential expressions between the duplicated piwi copies: while Api-piwi2 and Api-piwi6 are "specialised" in germ cells their most closely related copy, respectively Api-piwi5 and Api-piwi3, are expressed in the somatic cells. The differential expression was also identified in duplicated ago3: Api-ago3a in germ cells and Api-ago3b in somatic cells. Moreover, analyses of expression profiles of the expanded piwi and ago3 genes by semi-quantitative RT-PCR showed that expressions varied according to the reproductive types. These specific expression patterns suggest that expanded aphid piwi and ago3 genes have distinct roles in asexual and sexual reproduction.
authors.affiliation: Department of Entomology/Institute of Biotechnology, College of Bioresources and Agriculture, National Taiwan University, Taipei, Taiwan.
authors.forename: Hsiao-Ling
authors.initials: HL
authors.lastname: Lu
authors.forename: Sylvie
authors.initials: S
authors.lastname: Tanguy
authors.forename: Claude
authors.initials: C
authors.lastname: Rispe
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Gauthier
authors.forename: Tom
authors.initials: T
authors.lastname: Walsh
authors.forename: Karl
authors.initials: K
authors.lastname: Gordon
authors.forename: Owain
authors.initials: O
authors.lastname: Edwards
authors.forename: Denis
authors.initials: D
authors.lastname: Tagu
authors.forename: Chun-che
authors.initials: CC
authors.lastname: Chang
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Jaubert-Possamai
mesh_terms: D000818:Animals; D001042:Aphids / Q000378:metabolism*; D060565:Argonaute Proteins / Q000378:metabolism*; D019070:Cell Lineage; D003001:Cloning, Molecular; D018388:Codon, Terminator; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018745:Genome, Plant; D017403:In Situ Hybridization; D008954:Models, Biological; D008957:Models, Genetic; D016376:Oligonucleotides, Antisense / Q000235:genetics; D010802:Phylogeny; D034741:RNA, Small Interfering / Q000378:metabolism*; D012098:Reproduction; D012621:Seasons
chemical_list: D060565:Argonaute Proteins; D018388:Codon, Terminator; D016376:Oligonucleotides, Antisense; D034741:RNA, Small Interfering