Camptothecin-induced expression of programmed cell death gene 11 in Spodoptera litura

Camptothecin, one of the main active components of extract from the bark of the Chinese camptotheca tree, has been reported as a potent insecticide against various insect species. However, the mechanism of action of camptothecin as a botanical pesticide is not completely understood.

In this study, the full-length cDNA (GeneBank number JF681972) of Spodoptera litura programmed cell death protein 11 (pcdp 11) isoform 1 was cloned, sequenced and characterised. Quantitative real-time PCR (qRT-PCR) data showed that pcdp 11 was differentially expressed during the developmental stages, with significantly high expression during the transition from egg to larva and larva to pupa. Furthermore, pcdp 11 was upregulated in a time-dependent manner in SL-1 cells after treatment with 1.2 µg mL(-1) of camptothecin. The induced expression profile of pcdp 11 in the larval midgut after feeding camptothecin was visualised by fluorescence in situ hybridisation (FISH) and further quantified by qRT-PCR. Apoptosis in camptothecin-treated larval midguts was confirmed using terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining.

The results reveal a clear functional link between pcdp 11 expression and camptothecin-induced apoptosis, and prove that camptothecin exhibits strong toxicity towards S. litura by inducing midgut epithelial cell apoptosis.