Wnt Signaling Cross-Talks with JH Signaling by Suppressing Met and gce Expression

Abstract

Juvenile hormone (JH) plays key roles in controlling insect growth and metamorphosis. However, relatively little is known about the JH signaling pathways. Until recent years, increasing evidence has suggested that JH modulates the action of 20-hydroxyecdysone (20E) by regulating expression of broad (br), a 20E early response gene, through Met/Gce and Kr-h1. To identify other genes involved in JH signaling, we designed a novel Drosophila genetic screen to isolate mutations that derepress JH-mediated br suppression at early larval stages. We found that mutations in three Wnt signaling negative regulators in Drosophila, Axin (Axn), supernumerary limbs (slmb), and naked cuticle (nkd), caused precocious br expression, which could not be blocked by exogenous JHA. A similar phenotype was observed when armadillo (arm), the mediator of Wnt signaling, was overexpressed. qRT-PCR revealed that Met, gce and Kr-h1expression was suppressed in the Axn, slmb and nkd mutants as well as in arm gain-of-function larvae. Furthermore, ectopic expression of gce restored Kr-h1 expression but not Met expression in the arm gain-of-function larvae. Taken together, we conclude that Wnt signaling cross-talks with JH signaling by suppressing transcription of Met and gce, genes that encode for putative JH receptors. The reduced JH activity further induces down-regulation of Kr-h1expression and eventually derepresses br expression in the Drosophila early larval stages.

Comparative proteomic analysis of the silkworm middle silk gland reveals the importance of ribosome biogenesis in silk protein production

“…For example, the Wnt signaling pathway is involved in animal development. In Drosophila, it has been shown that Wnt signaling involves cross-talk with JH signaling by suppressing the transcription of genes that encode putative JH receptors [45]. This result further supports the role of MSG-A in silk gland development.…”

Comparative transcriptome analysis among parental inbred and crosses reveals the role of dominance gene expression in heterosis in Drosophila melanogaster

“…Approximately 90 cytochrome P450 genes exist in the Drosophila melanogaster genome 36 and are involved in hormone biosynthesis and metabolism, (e.g., insect juvenile hormone (JH)) 37 38 39 . JH plays an essential role in insect development, metamorphosis, and reproduction 40 41 . The heterosis for body weight may therefore be modulated by these pathways.…”

Transcriptomic analysis of developmental features of Bombyx mori wing disc during metamorphosis

“…Insect metamorphosis is mediated by 20E and JH signals. During larval stage, JH exhibits its "status quo" function probably through two transcription factors, E75A and Kr-h1, to prevent the activation of BR-C , a 20E signal transduction gene for larvae-pupae transition [ 7 , 47 ]. Though a relative high titer of JH was present in hemolymph of B. mori at the end of the final instar larvae [ 48 ], the JH does not inhibit the wing disc transformation.…”