Computational identification and evolutional analysis of Piwi subfamily in 11 Drosophila species

• Published in: Insect science 2008-12, Vol.15 (6), p.537-544
• Main Authors: Zhou, Xue, Xu, Ya-Long, Cheng, Luo-Gen, Li, Fei
• Format: Article
• Language: English
• Subjects: Drosophila; Drosophila genome; evolution; intron; Piwi; subfamily
• ISSN: 1672-9609; 1744-7917
• DOI: 10.1111/j.1744-7917.2008.00243.x

The complete genome sequences of 11 Drosophila species provide an opportunity to investigate the gene family evolution in closely related species. Drosophila Piwi subfamily, including three members, piwi, Aub and Ago3, has attracted increasing attention as it participates in the biogenesis of piRNA. Here, we identified 33 Piwi homologs from the genome of 11 Drosophila species. The full‐length cDNA sequences of piwi and Aub genes were obtained by using New GENSCAN Web Server. The Ago3 homologs were difficult regarding full‐length information because they had long introns. The genomic structure of Piwi subfamily genes are highly conserved among diverse Drosophila species. Insect piwi and Aub genes have long first introns. The average length of the first intron is 1 284 bp for piwi and 840 bp for Aub, which is much larger than those of other introns (93 bp for Piwi and 54 bp for Aub). However, this phenomenon is not observed in mammalian piwi genes. We also found that there were abundant repeat sequences in both exons and introns of insect Ago3 genes. Due to recent insertions of long terminal repeat elements in four Drosophila species, part of the third introns exhibit higher conservation than adjacent exons and other introns. An evolutional tree created by Minimum Evolution method indicates that mammalian piwi genes are more closely related to the insect Ago3 Piwi subfamily.