Insulin-like peptides (
ILPs) mediate various physiological processes in insects. Specifically,
ILP expression is required for immature development in different insects. The western flower thrips,
Frankliniella occidentalis, is polyphagous, but its occurrence and population density vary among different hosts. This study assesses
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Insulin-like peptides (
ILPs) mediate various physiological processes in insects. Specifically,
ILP expression is required for immature development in different insects. The western flower thrips,
Frankliniella occidentalis, is polyphagous, but its occurrence and population density vary among different hosts. This study assesses the developmental variations in the thrips through quantitative analysis of their
ILP expressions. Two types of
ILPs (
Fo-ILP1 and
Fo-ILP2) were identified from the genome of
F. occidentalis, and both
ILPs were predicted to have the characteristics of signal peptides and B-C-A chains linked by cysteines. A phylogenetic analysis indicates that these two
ILPs in the thrips are clustered with the
ILP1 of
Drosophila melanogaster, suggesting their physiological roles in growth. In addition, the two
ILP genes were relatively highly expressed at all feeding stages, but their expression was reduced during the nonfeeding prepupal and pupal stages. Furthermore, RNA interference of each
ILP expression led to significant developmental retardation. In validating the
ILP expression in the thrips’ development, five different varieties of host hot peppers were assessed in a choice test, along with the immature development of
F. occidentalis. The expression levels of the two
ILP genes were highly correlated with variations in the immature developmental rates of different hot pepper varieties. These suggest that
Fo-ILP1 and
Fo-ILP2 mediate the immature development of
F. occidentalis by sensing different nutritional values of hot peppers. This study is the first report on
ILPs in thysanopteran insects.
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