Transcription Factor FOXO Regulates Juvenile Hormone Degradation in Insects
Juvenile hormone (JH), ecdysone and insulin are major hormones which control most of insect physiological processes. Their homeostasis is thus critical for properly controlling insect growth and development. In previous studies, the insulin signaling downstream transcription factor FOXO has been reported to be involved in multiple physiological processes. However, the mechanism of how FOXO coordinates major hormone signaling pathways to regulate insect growth and development remains uncovered.
In the present study, Professor TAN Anjiang and his colleagues at Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, investigated the role of FOXO in JH signaling using the silkworm, Bombyx mori, a lepidopteran model insect with economic importance as a model.
Generating somatic FOXO mutants via the transgenic CRISPR/Cas9 system to exploit biological functions of silkworm FOXO, they found that depletion of FOXO induced growth delay and precocious metamorphosis, which is a typical JH-deficient consequence. Mutant larvae underwent only three times of ecdysis before entering pupal stage, comparing with four times of ecdysis in wild type animals.
However, this consequence can be rescued by application of either JH or ecdysteroids, indicating more complicated mechanism than previous reported ones. Using RNA-seq analysis, researchers identified that expression of several key genes in JH inactivation pathway were significantly up-regulated in FOXO mutants. EMSA analysis further revealed that FOXO-responsible elements were presented in the promoter regions of these genes.
Overall, these findings provide the first evidence that FOXO interacts with JH degradation, revealing the complexity of hormone regulation on insect growth and development.
TAN Anjiang, Ph.D.,
Key Laboratory of Insect Developmental and Evolutionary Biology
Institute of Plant Physiology and Ecology (SIPPE)
Chinese Academy of Sciences (CAS)
300 Fenglin Road, Shanghai 200032, China