The FOXO transcription factor controls insect growth and development by regulating juvenile hormone degradation in the silkworm, Bombyx mori

Abstract

Forkhead box O (FOXO) functions as the terminal transcription factor of the insulin signaling pathway and regulates multiple physiological processes in many organisms, including lifespan in insects. However, how FOXO interacts with hormone signaling to modulate insect growth and development is largely unknown. Here, using the transgene-based CRISPR/Cas9 system, we generated and characterized mutants of the silkworm FOXO () to elucidate its physiological functions during development of this lepidopteran insect. The mutant (FOXO-M) exhibited growth delays from the first larval stage and showed precocious metamorphosis, pupating at the end of the fourth instar (trimolter) rather than at the end of the fifth instar as in the wild-type (WT) animals. However, different from previous reports on precocious metamorphosis caused by juvenile hormone (JH) deficiency in silkworm mutants, the total developmental time of the larval period in the FOXO-M was comparable with that of the WT. Exogenous application of 20-hydroxyecdysone (20E) or of the JH analog rescued the trimolter phenotype. RNA-seq and gene expression analyses indicated that genes involved in JH degradation but not in JH biosynthesis were up-regulated in the FOXO-M compared with the WT animals. Moreover, we identified several FOXO-binding sites in the promoter of genes coding for JH-degradation enzymes. These results suggest that FOXO regulates JH degradation rather than its biosynthesis, which further modulates hormone homeostasis to control growth and development in In conclusion, we have uncovered a pivotal role for FOXO in regulating JH signaling to control insect development.

Genotype to phenotype: Diet-by-mitochondrial DNA haplotype interactions drive metabolic flexibility and organismal fitness

“…There were 14 differentially upregulated KEGG pathways (p< 0.01) and eight differentially downregulated KEGG pathways (p< 0.01) in Dahomey compared to Alstonville larvae ( Fig 7B and S3C & S3D Table ). Of the 14 differentially upregulated pathways in Dahomey at least three (replication, Notch, and FOXO signalling) have been associated with development [ 127 , 128 ]. Gene Ontology analyses of the two mitotypes on the two diets shows annotations with low probability ( S4C & S4D Table ).…”

Monarch butterflies use an environmentally sensitive, internal timer to control overwintering dynamics

“…JH promotes IIS in Tribolium castaneum (Xu, Sheng, & Palli, ), which may provide a mechanism by which IIS is reduced via dp‐foxo . FOXO has been shown to regulate JH degradation in B. mori (Zeng et al, ), which suggests an additional, orthologous mechanism by which JH accumulates slowly in summer conditions when met during diapause. This model highlights how extensive crosstalk between these developmental hormones can render this integrated network vulnerable to a single perturbation, leading to a completely reorganized hormonal landscape that changes organismal function.…”

A palmitoyltransferase Approximated gene Bm‐app regulates wing development in Bombyx mori

“…In Drosophila , the existence of the Hippo pathway coordinates multiple physiological processes, including developmental patterning, proliferation, apoptosis and cell growth, to regulate overall organ size (Boggiano & Fehon, ; Enderle & McNeill, ; Hariharan, ). In B. mori , all key components of the Hippo pathway exist (Liu et al ., ; Zeng et al ., ) and genes involved in the Hippo pathway are particularly enriched in several mitotic tissues, including the ovary, testis and wing disc in B. mori (Zeng et al ., ; Cao et al ., ). In the current study, although expressions of Ds and Ft did not show significant alteration, the Hippo kinase cassette genes Hippo , Warts and Mats , which play a part for inhibiting excessive cell proliferation, were significantly up‐regulated.…”

“…Recently, genome‐editing tools such as ZFN (zinc‐finger nucleases), TALEN (transcription‐activator like effector nucleases) and the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA‐guided Cas9 nucleases) systems have been applied in functional gene analysis in different organisms (Hruscha et al ., ; Wang et al ., ). In B. mori , these techniques have also been successfully established (Wang et al ., ; Li et al ., ; Xu et al ., ; Zeng et al ., ), providing effective loss‐of‐function toolkits to explore the mechanisms for silkworm natural mutants such as mw .…”