SEQUENCE ANALYSIS OF INSECTICIDE RESISTANCE AND DETOXIFICATION RELATED GENES IN Spodoptera littoralis(LEPIDOPTERA: NOCTUIDAE)

Abstract

The Egyptian cotton leaf worm, Spodoptera littoralis (Boisd. ) is a well-known asone of the most destructive agricultural lepidopterous pests. It is a true generalistspecies with a promiscuous feeding strategy which enables it to attack numerouseconomically important crops all year round including vegetables, ornamentalplants, and cotton. Recently, chemical control has been commonly used to suppresspopulations of S. littoralis; however, a very large number of insecticides have ledtothe emergence ofresistance. An extensive use of insecticides also has other sideeffects, including the elimination of non-targeted organisms, environmentaldamage and harm to human health. Genome-wide high-throughput technologieshelp developing resistance management strategies, especially identifying geneticmechanisms of resistance. The aim of the present study was to produce a de novotranscriptome for S. littoralis as a resource for current and future studies of thispest species by using next-generation sequencing. This resource was then used as areference for identifying genes by encoding the target sites of insecticides currentlyin use for Egyptian cotton leaf worm control. To achieve this, a cDNA library wassequenced using 454 FLX Titanium Sequencing on the Roche platform whichrevealed good coverage of genes encoding insecticide target sites anddetoxification enzymes using a manual annotation. Annotations of assembledsequences were carried out by BLASTx against NCBI non-redundant proteinsequence databases using the software Blast2GO. The genesencodingenzymesinvolvedin insecticide detoxification such as Acetylcholinesterase,Cytochrome p450, Glutathione S-transferase were characterized. Furthermore, aphylogenetic analyses based on three protein sequences were generated in order togive evolutionary insights into insecticide resistance gene families of S. littoralis.