RNAi Control of Tobacco Thrips: Ilumina Transcriptomics

The whole-body transcriptome for nymphs of the tobacco thrips was sequenced on an Illumina® Genome Analyzer IIx sequencer.  Illumina sequences produced 6.6 gigabases of sequence data distributed across 66 million 101-base reads.  Approximately 55% of these reads had a minimum quality score of Q20 across the entire length of the read and 85% of the bases among all reads had a minimum quality score of Q30.  The reads were assembled with Trinity® software into 64,280 contiguous sequences (contigs).  The contig lengths ranged from approximately 100 bps (base pairs) to greater than 2,000 bps.  The assembled contigs were batched BLASTed, mapped and annotated with Blast2GO® software.  The number of contigs with BLAST hits was 22,174.  The vast majority of these were associated in the order of highest to lowest number of GO (Gene Ontology) assignments to binding, catalytic activity, transporter activity, structural molecular activity and molecular transducer activity.  To illustrate the depth of contig information in our global putative functional analysis, messages are further characterized which are involved in hormonal regulation of development, steps in juvenile hormone (JH) biosynthesis, critical messages involved in JH degradation and ecdysteroid metabolism, known commercial insecticide targets, and enzymes involved in general in insecticide detoxification. There results provide many new leads for the development of both RNAi and artificial antibody approaches of control of this important insect pest of cotton and other crops where currently there is no commercial plant transgenic approach to tobacco thrips control.  In addition, this transcriptome provides opportunities for the global evaluation of risk to insecticide resistance, the study of plant virus transmission and insect vectored-plant diseases in general, and the study of the basic physiology and ecology of tobacco thrips and the crops on which they feed.