An insulin-like growth factor-like peptide promotes ovarian development in the silkmoth Bombyx mori

Insulin family peptides are known to be key regulators of growth and metabolism in insects and vertebrates. Insects have two types of insulin family peptides: insulin-like peptides and insulin-like growth factor (IGF)-like peptides (IGFLPs). We recently demonstrated that an IGFLP in the silkmoth, Bombyx mori (BIGFLP) promotes the growth of the genital imaginal disc ex vivo. However, the role of BIGFLP in the regulation of insect growth remains unclear because no in vivo study has been performed. Therefore, we analysed the functions of BIGFLP in vivo by constructing BIGFLP knock-out (KO) B. mori using the clustered regularly interspaced palindromic repeats (CRISPR) and CRISPR-associated protein 9 (CRISPR-Cas9) system. The KO moths exhibited decreased body weights and size of the appendages compared wild-type (wt) moths. Interestingly, KO females also had drastically lower ovary weights and number of eggs than wt females. However, mutant ovaries that were transplanted into wt host pupae reached a similar weight to wt ovaries that were transplanted into the wt hosts, suggesting that IGFLP in the haemolymph promotes ovarian development. These findings show that BIGFLP regulates the growth and development of adult organs, particularly the ovaries, in B. mori.

The Drosophila sex determination hierarchy modulates wingless and decapentaplegic signaling to deploy dachshund sex-specifically in the genital imaginal disc

The integration of multiple developmental cues is crucial to the combinatorial strategies for cell specification that underlie metazoan development. In the Drosophila genital imaginal disc, which gives rise to the sexually dimorphic genitalia and analia, sexual identity must be integrated with positional cues, in order to direct the appropriate sexually dimorphic developmental program. Sex determination in Drosophila is controlled by a hierarchy of regulatory genes. The last known gene in the somatic branch of this hierarchy is the transcription factor doublesex (dsx); however, targets of the hierarchy that play a role in sexually dimorphic development have remained elusive. We show that the gene dachshund (dac) is differentially expressed in the male and female genital discs, and plays sex-specific roles in the development of the genitalia. Furthermore, the sex determination hierarchy mediates this sex-specific deployment of dac by modulating the regulation of dac by the pattern formation genes wingless (wg) and decapentaplegic (dpp). We find that the sex determination pathway acts cell-autonomously to determine whether dac is activated by wg signaling, as in females, or by dpp signaling, as in males.

Compartmental organization of the Drosophila genital imaginal discs

We have investigated the anterior and posterior compartmental organization of the genital imaginal disc. Unlike the thoracic discs, the genital disc is a compound disc consisting of three primordia--the female genital, male genital, and anal primordia. Here we provide evidence that each primordium is divided into anterior and posterior compartments. Genes that are known to be expressed in compartment-specific manners in other discs (engrailed, hedgehog, patched, decapentaplegic, wingless and cubitus interruptus) are expressed in analogous patterns in each primordium of the genital disc. Specifically, engrailed and cubitus interruptus are expressed in complementary domains, while patched, decapentaplegic and wingless are expressed along the border between the two domains. Mitotic clones induced at the beginning of the second larval instar do not cross the boundary between the engrailed-expressing and cubitus interruptus-expressing domains, indicating that these domains are true genetic compartments. Furthermore, we examined the phenotypes of mutant clones of the cAMP-dependent protein kinase A and engrailed-invected, genes that are known to play compartment-specific functions in other discs. These experiments demonstrate that the anterior/posterior patterning functions of these genes are conserved in the genital disc. The adult clonal phenotypes of protein kinase A and engrailed-invected mutants also provide a more detailed map of the adult genitalia and analia with respect to the anterior/posterior compartmental subdivision. Our results lead us to propose a new model to describe the anterior and posterior compartmental organization of the genital disc.

Developmental expression of the glucose dehydrogenase gene in Drosophila melanogaster.

The Gld gene of Drosophila melanogaster is transiently expressed during every stage of development. The temporal pattern of Gld expression is highly correlated with that of ecdysteroids. Exogeneous treatment of third instar larvae with 20-hydroxyecdysone induces the accumulation of Gld mRNA in the hypoderm and anterior spiracular gland cells. During metamorphosis Gld is expressed in a variety of tissues derived from the ectoderm. In the developing reproductive tract, Gld mRNA accumulates in the female spermathecae and oviduct and in the male ejaculatory duct and ejaculatory bulb. These four organs are derived from closely related cell lineages in the genital imaginal disc. Since the expression of Gld is not required for the development of these reproductive structures, this spatial pattern of expression is most likely a fortuitous consequence of a shared regulatory factor in this cell lineage. At the adult stage a high level of the Gld mRNA is only observed in the male ejaculatory duct.