Expressed Sequence Tags (ESTs) analysis of Tenebrio molitor larvae

Abstract

Tenebrio molitor has been seriously investigated as a model insect in elucidating Toll signaling pathway and related regulators of innate immunity. However, little is known with regards to the genomic information in T.molitor. In an attempt towards exploiting the rich transcriptomics data that would offer further insights into the study on insect immunity through potential screening of immune-related genes in the model insect, we constructed a cDNA library (library titer = 5.0 x 105pfu/ml) of T.molitor larvae and analyzed expressed sequence tag (EST) sequences from 1056 clones. The base calling and quality check of obtained chromatogram files were performed by using the Phred program (trim_alt 0.05 (P-score>20). After removal of vector and 100 bp and less sequences, 1023 sequences were generated having an average insert size of 792 bp, including 160 clusters, 164 contigs and 387 singletons through clustering and assembling process using the TGI Clustering Tools (TGICL) package. The unique EST sequences were searched against the NCBI nr database by local BLAST (blastx, E < e5) with 940 sequences showing significant hits. Subsequently, KOG (clusters of orthologous groups for eukaryotic complete genomes) analysis was conducted (blastx, E < e10) towards prediction of transcriptomal functions, leading to the categorization of 638 genes. The majority of genes belonged to Z category (cytoskeleton-related genes), R category (general function prediction), and C category (energy production and conversion related genes). These basic EST datasets and their bioinformatics analysis will be helpful in investigating the biological mechanism and molecular pathway related genes involved in innate immunity mechanisms of T.molitor.