Inscet cytokine growth-blocking peptide (GBP) regulates density-dependent cuticular melanism in armyworm, Pseudaletia separate

Cuticular melanization is one of the forms of phase polyphenism in lepidopteran insects in which the expression of a variety of traits can be affected by local population density. We tested for the expression of density-dependent cuticular melanization in the armyworm, Mythimna separata. When reared at high densities, the larvae exhibited darker cuticular melanization than larvae reared at low densities. The functional regulation of insect cytokine growth-blocking peptide (GBP) in the density-dependent color change was investigated. It demonstrated that the gene expression of GBP in armyworm increased with the population density of larvae. In order to confirm further the regulation mechanisms of GBP in cuticular melanization, we used direct injection of protein GBP into the body of larvae and compared the difference of cuticular melanization before and after the treatments. Other studies including the silencing of gene GBP with RNAi techniques were also under investigation.

Key words: Mythimna separate, Growth blocking peptide (GBP), Density-dependent, Cuticular melanization, RNAi