摘要
Nine piggyBac-like elements （PLEs） were identified from the cotton aphid Aphis gossypii Glover. All the PLEs shared high sequence similarity with each other. However, eight of the nine PLEs were unlikely to encode functional transposase due to the existence of disruptive mutations within the coding regions. The other one PLE contained major characteristics of members in the piggyBac family, including TTAA target site duplications, inverted terminal repeats （ITRs）, and an open reading frame （ORF） coding for a transposase with a putative DDD domain. This one with an intact transposase ORF was named AgoPLE1.1. The predicted transposase shared 47% similarity with that of Trichoplusia ni piggyBac IFP2. Phylogenetic analyses showed that AgoPLE1.1 was most related to the Heliothis virescens PLE1.1 （HvPLE1.1） element, with 45% and 60% similarity at the nucleotide and amino acid levels, respectively. A functional assay demonstrated that AgoPLE1.1 encoded a functional transposase and was able to cause precise excision in cell cultures. On the other hand, few genomic insertion polymorphisms of AgoPLEI were observed in the genome of the cotton aphid. These observations suggested that AgoPLE1.1 was a PLE that invaded the cotton aphid genome in recent periods and retained its activity.
Nine piggyBac-like elements （PLEs） were identified from the cotton aphid Aphis gossypii Glover. All the PLEs shared high sequence similarity with each other. However, eight of the nine PLEs were unlikely to encode functional transposase due to the existence of disruptive mutations within the coding regions. The other one PLE contained major characteristics of members in the piggyBac family, including TTAA target site duplications, inverted terminal repeats （ITRs）, and an open reading frame （ORF） coding for a transposase with a putative DDD domain. This one with an intact transposase ORF was named AgoPLE1.1. The predicted transposase shared 47% similarity with that of Trichoplusia ni piggyBac IFP2. Phylogenetic analyses showed that AgoPLE1.1 was most related to the Heliothis virescens PLE1.1 （HvPLE1.1） element, with 45% and 60% similarity at the nucleotide and amino acid levels, respectively. A functional assay demonstrated that AgoPLE1.1 encoded a functional transposase and was able to cause precise excision in cell cultures. On the other hand, few genomic insertion polymorphisms of AgoPLEI were observed in the genome of the cotton aphid. These observations suggested that AgoPLE1.1 was a PLE that invaded the cotton aphid genome in recent periods and retained its activity.
基金
Acknowledgments We thank Professor T. A. Miller from the University of California, Riverside, CA for his kindness in providing the helper pBacHsp and donor pB[KOα] plasmid. This work was supported by a national project for basic research （2006CB 102003）, China postdoctoral science foundation （20090451226）, and IAEA project （15686/RO/RBF）.
