The potential role of FoxO transcription factor during postembryonic periods in the silkworm, Bombyx mori (Lepidoptera: Bombycidae).

The Forkhead box O (FoxO) transcription factors, including FoxO1, FoxO3a, and FoxO4, have been implicated in the regulation of several biological processes, including stress resistance, metabolism, and apoptosis. In the present study, FoxO1 and FoxO3a patterns and their role in the regulation of the insulin signalling and mitogen-activated protein kinase (MAPK) pathways were analyzed after starvation in the fat body cells of the silkworm, Bombyx mori. FoxO1 and FoxO3a are localized to the nuclei. It was found that the levels of the insulin receptor and phosphoryated kinase Akt (p-Akt) increased when the animals ceased feeding. Starvation conditions caused a decrease in extracellular-signal-regulated kinase (ERK) phosphorylation, and an increase in c-Jun N-terminal kinase (JNK) and p38 (MAP kinase) phosphorylation. This implies that the FoxO transcription factors are activated by starvation and that starvation leads to changes in the insulin signalling and MAPK pathways in B. mori. These results strongly suggest that the FoxO transcription factor may be involved in the regulation of the insulin signalling and MAPK pathways in B. mori. As such, the findings provide molecular entomologists with valuable information on the molecular mechanism of the signalling pathways in postembryonic development ofthe silkworm. [ABSTRACT FROM AUTHOR]