Expressed sequence tag analysis of the predatory mite Phytoseiulus persimilis Athias Henriot (Acari: Phytoseiidae)

We present results from an analysis of cDNA sequences from Phytoseiulus persimilis, a predatory mite specialist on spider mites (Tetranychidae), which are serious pests in field and greenhouse crops. Variation in several foraging traits affecting predatory efficiency of this pest control agent has been shown to be based on significant heritable differences, and we are interested in the genetic mechanisms underlying that variation. We started a genomic approach to study foraging behavior of P. persimilis, aiming development of genetic tools for applications in biological control.

A cDNA library was construction by a PCR amplification method (SMART library construction method, Clonetech). The library was normalized to enhance gene discovery rate and the identification of rare transcripts. Amplified cDNA was normalized using duplex-specific nuclease method prior to library cloning. A total of 960 randomly selected clones were sequenced for both directions (average insert size of 1.2 Kb). The sequences were pre-joined for each direction of the sequences for the clone. Assembly of these sequences revealed 767 UniEST with 59 contigs. Putative functions were assigned to 400 uniESTs that exhibited strong similarity to genes in public databases. About 32% of annotated sequences are involved in protein binding activity. At least 15 putative genes are related to chemosensory, locomotion and behavioral interactions. We also found at least 100 UniEST sequences that have respective putative orthology with the genes found in insects (Drosophila melanogaster, Apis mellifera, and Tribolium castaneum) and in Caenorhabditis elegans, which allow details of analysis of the molecular evolution.