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 as
one of the most destructive agricultural lepidopterous pests. It is a true generalist
species with a promiscuous feeding strategy which enables it to attack numerous
economically important crops all year round including vegetables, ornamental
plants, and cotton. Recently, chemical control has been commonly used to suppress
populations of S. littoralis; however, a very large number of insecticides have ledto
the emergence ofresistance. An extensive use of insecticides also has other side
effects, including the elimination of non-targeted organisms, environmental
damage and harm to human health. Genome-wide high-throughput technologies
help developing resistance management strategies, especially identifying genetic
mechanisms of resistance. The aim of the present study was to produce a de novo
transcriptome for S. littoralis as a resource for current and future studies of this
pest species by using next-generation sequencing. This resource was then used as a
reference for identifying genes by encoding the target sites of insecticides currently
in use for Egyptian cotton leaf worm control. To achieve this, a cDNA library was
sequenced using 454 FLX Titanium Sequencing on the Roche platform which
revealed good coverage of genes encoding insecticide target sites and
detoxification enzymes using a manual annotation. Annotations of assembled
sequences were carried out by BLASTx against NCBI non-redundant protein
sequence databases using the software Blast2GO. The genesencoding
enzymesinvolvedin insecticide detoxification such as Acetylcholinesterase,
Cytochrome p450, Glutathione S-transferase were characterized. Furthermore, a
phylogenetic analyses based on three protein sequences were generated in order to
give evolutionary insights into insecticide resistance gene families of S. littoralis.