Year-end Sale % OFF 
Abstract
BackgroundSpecific genomic loci, termed Piwi-interacting RNA (piRNA) clusters, manufacture piRNAs that serve as guides for the inactivation of complementary transposable elements (TEs). The piRNA pathway has been accurately detailed in Drosophila melanogaster, while it remains poorly examined in other insects. This pathway is increasingly recognized as critical for germline development and reproduction. Understanding of the piRNA functions in mosquitoes could offer an opportunity for disease vector control by the reduction of their reproductive potential.ResultsTo analyze the similarities and differences in this pathway between Drosophila and mosquito, we performed an in-depth analysis of the genomic loci producing piRNAs and their targets in the African malaria vector Anopheles gambiae. We identified 187 piRNA clusters in the An. gambiae genome and 155 piRNA clusters in the D. melanogaster genome. We demonstrate that many more piRNA clusters in the mosquito compared with the fruit fly are uni-directionally transcribed and are located outside pericentromeric heterochromatin. About 11 % of the An. gambiae piRNA population map to gene transcripts. This is a noticeable increase compared with the ~6 % of the piRNA population mapped to genes in D. melanogaster. A subset of the piRNA-enriched genes in An. gambiae has functions related to reproduction and development. At least 24 and 65 % of the mapped piRNAs correspond to genomic TE sequences in An. gambiae and D. melanogaster, respectively. DNA transposons and non-LTR retrotransposons are more abundant in An. gambiae, while LTR retrotransposons are more abundant in D. melanogaster. Yet, piRNAs predominantly target LTR retrotransposons in both species, which may point to a distinct feature of these elements compared to the other classes of TEs concerning their silencing by the piRNA pathway.ConclusionsHere, we demonstrate that piRNA-producing loci have more ubiquitous distribution in the An. gambiae genome than in the genome of D. melanogaster. Also, protein-coding genes have an increased role in production of piRNAs in the germline of this mosquito. Genes involved in germline and embryonic development of An. gambiae generate a substantial portion of piRNAs, suggesting a role of the piRNA pathway in the epigenetic regulation of the reproductive processes in the African malaria vector.Electronic supplementary materialThe online version of this article (doi:10.1186/s13072-015-0041-5) contains supplementary material, which is available to authorized users.
Highlights
Specific genomic loci, termed Piwi-interacting RNA clusters, manufacture Piwi-interacting RNAs (piRNAs) that serve as guides for the inactivation of complementary transposable elements (TEs)
We discovered a noticeable shift in piRNA cluster location in An. gambiae compared with D. melanogaster; the 15 most productive piRNA clusters are less confined to the pericentromeric heterochromatin, but can be found in intercalary heterochromatin and euchromatin
The piRNA population in the ovarian tissue of An. gambiae To accurately characterize the sequence and genomic location of piRNAs produced by the African malaria vector, we isolated and sequenced small RNAs from blood-fed ovaries of the Mali strain of An. gambiae using the Illumina Small RNA TruSeq technology
Summary
Specific genomic loci, termed Piwi-interacting RNA (piRNA) clusters, manufacture piRNAs that serve as guides for the inactivation of complementary transposable elements (TEs). The piRNA pathway has been accurately detailed in Drosophila melanogaster, while it remains poorly examined in other insects This pathway is increasingly recognized as critical for germline development and reproduction. A mutation of any of the three key PIWI proteins—Piwi, Aubergine (Aub), and Argonaute 3 (Ago3)—results in de-repression of TEs with mutagenic or disruptive consequences in the Drosophila melanogaster germline [3,4,5], indicating the necessity of these proteins in functional TE silencing. Trimming of the piRNA to the 24–30 nt characteristic size of these small RNAs requires the cytoplasmic endonuclease Zucchini [6, 7] In another mechanism, secondary piRNAs, responsible for a large portion of the total piRNA pool in the germline, are generated through an amplification loop referred to as the ping-pong cycle [2] and loaded onto Ago. Many piRNAs associating with the Aubergine and Piwi proteins are antisense to TEs and show a typical 1U feature, while piRNAs associated with Argonaute 3 are sense to the TE transcripts and show a 10A feature
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
