De novo transcriptomics based identification and characterization of genes involved in spinosad resistance in the egg parasitoid, Trichogramma chilonis Ishii

Trichogramma
chilonis (Hymenoptera:
Trichogrammatidae), an effective egg parasitoid, commonly
used as an innundative biocontrol agent for the management of many lepidopteron
pests worldwide. However, its biocontrol potential is severely hampered due to application
of broad spectrum of insecticides against insect pests on different crops. Therefore,
development of an insecticide tolerant T.
chilonis would be very useful and compatible with
chemical control to manage the insect pests under insecticide stressed
conditions especially in Integrated Pest management Programmes. Furthermore
such strategy would reduce the pesticide load on the crops and would protect
the non target organisms. Therefore, a spinosad (45% SC) resistant T.
chilonis was selected by continuously exposing to
the spinosad for 35 generations and its dosage mortality and quantification of
detoxifying enxymes viz., glutathione S-transferases and cytochrome p-450
monooxygenases was done in comparison
with susceptible laboratory strain. Furthermore, the spinosad
susceptible and resistance strain of T. chilonis were sequenced using high
throughput RNA sequencing with
the aim to identify the molecular mechanism associated with spinosad resistance.
De
novo transcriptome analysis showed 1026
differentially expressed genes including 654 and 332 up and down-regulated genes,
respectively in the spinosad resistant strain of T. chilonis. Multiple transcripts were associated with already known
insecticide targets including cuticle, oxidative phosphorylation and metabolic
process. qRT-PCR analysis of 10 differentially expressed genes confirmed the pattern observed in the
transcriptome sequencing expression profiles. These finding provide a valuable
resource for future studies into the molecular mechanisms underlying
insecticide resistance in biocontrol agents like parasitoids and predators.