Transgenic expression of <i>Dendrolimus kikuchii</i> nucleopolyhedrovirus enhancin in tobacco enhances the mortality and affects the development of <i>Spodoptera exigua</i> larvae

A novel 2551-bp enhancin gene designated <i>En-Dk</i> was isolated from the <i>Dendrolimus kikuchii</i> nucleopolyhedrovirus genome<i>.</i> Sequence analysis revealed that <i>En-Dk</i> encodes a polypeptide chain of 792 amino acid residues containing a conserved enhancin domain and an α-helical transmembrane domain, but no signal peptide. Compared with wild-type tobacco (<i>Nicotiana tabacum</i> L.), transgenic tobacco showed significant phenotypic changes following <i>En-Dk</i> overexpression with slower growth and delayed initial flowering. An interesting finding is that the transgenic tobacco exerted a toxic effect on newly hatched <i>Spodoptera exigua</i> larvae, with a significant inhibitory effect on third-instar larvae in terms of body weight, pupal weight, pupation and the emergence process.