Flexible manipulation of Omb levels in the endogenous expression region of Drosophila wing by combinational overexpression and suppression strategy

Osiris17 is essential for stable integrin localization and function during insect wing epithelia remodeling

The dynamic adhesion between cells and their extracellular matrix is essential for the development and function of organs. During insect wing development, two epithelial sheets contact each other at their basal sites through the interaction of βPS integrins with the extracellular matrix. We report that Osiris17 contributes to the maintenance of βPS integrins localization and function in developing wing of Drosophila and locust. In flies with reduced Osiris17 expression the epithelia sheets fail to maintain the integrity of basal cytoplasmic junctional bridges and basal adhesion. In contrast to the continuous basal integrin localization in control wings, this localization is disrupted during late stages of wing development in Osiris17 depleted flies. In addition, the subcellular localization revealed that Osiris17 co-localizes with the endosomal markers Rab5 and Rab11. This observation suggests an involvement of Osiris17 in endosomal recycling of integrins. Indeed, Osiris17 depletion reduced the numbers of Rab5 and Rab11 positive endosomes. Moreover, overexpression of Osiris17 increased co-localization of Rab5 and βPS integrins and partially rescued the detachment phenotype in flies with reduced βPS integrins. Taken together, our data suggest that Osiris17 is an endosome related protein that contributes to epithelial remodeling and morphogenesis by assisting basal integrins localization in insects.

Demonstration of RNAi Yeast Insecticide Activity in Semi-Field Larvicide and Attractive Targeted Sugar Bait Trials Conducted on Aedes and Culex Mosquitoes

Eco-friendly new mosquito control innovations are critical for the ongoing success of global mosquito control programs. In this study, Sh.463_56.10R, a robust RNA interference (RNAi) yeast insecticide strain that is suitable for scaled fermentation, was evaluated under semi-field conditions. Inactivated and dried Sh.463_56.10R yeast induced significant mortality of field strain Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus larvae in semi-field larvicide trials conducted outdoors in St. Augustine, Trinidad, where 100% of the larvae were dead within 24 h. The yeast was also stably suspended in commercial bait and deployed as an active ingredient in miniature attractive targeted sugar bait (ATSB) station sachets. The yeast ATSB induced high levels of Aedes and Culex mosquito morbidity in semi-field trials conducted in Trinidad, West Indies, as well as in Bangkok, Thailand, in which the consumption of the yeast resulted in adult female mosquito death within 48 h, faster than what was observed in laboratory trials. These findings support the pursuit of large-scale field trials to further evaluate the Sh.463_56.10R insecticide, a member of a promising new class of species-specific RNAi insecticides that could help combat insecticide resistance and support effective mosquito control programs worldwide.

Chitinase 6 is required for procuticle thickening and organ shape in Drosophila wing

The polysaccharide chitin is a major scaffolding molecule in the insect cuticle. In order to be functional, both chitin amounts and chitin organization have been shown to be important parameters. Despite great advances in the past decade, the molecular mechanisms of chitin synthesis and organization are not fully understood. Here, we have characterized the function of the Chitinase 6 (Cht6) in the formation of the wing, which is a simple flat cuticle organ, in the fruit fly Drosophila melanogaster. Reduction of Cht6 function by RNA interference during wing development does not affect chitin organization, but entails a thinner cuticle suggesting reduced chitin amounts. This phenotype is opposed to the one reported recently to be caused by reduction of Cht10 expression. Probably as a consequence, cuticle permeability to xenobiotics is enhanced in Cht6-less wings. We also observed massive deformation of these wings. In addition, the shape of the abdomen is markedly changed upon abdominal suppression of Cht6. Finally, we found that suppression of Cht6 transcript levels influences the expression of genes coding for enzymes of the chitin biosynthesis pathway. This finding indicates that wing epidermal cells respond to activity changes of Cht6 probably trying to adjust chitin amounts. Together, in a working model, we propose that Cht6-introduced modifications of chitin are needed for chitin synthesis to proceed correctly. Cuticle thickness, according to our hypothesis, is in turn required for correct organ or body part shape. The molecular mechanisms of this processes shall be characterized in the future.

Decapentaplegic retards lipolysis during metamorphosis in Bombyx mori and Drosophila melanogaster

Insect morphogen decapentaplegic (Dpp) functions as one of the key extracellular ligands of the Bone Morphogenetic Protein (BMP) signaling pathway. Previous studies in insects mainly focused on the roles of Dpp during embryonic development and the formation of adult wings. In this study, we demonstrate a new role for Dpp in retarding lipolysis during metamorphosis in both Bombyx mori and Drosophila melanogaster. CRISPR/Cas9-mediated mutation of Bombyx dpp causes pupal lethality, induces an excessive and premature breakdown of lipids in the fat body, and upregulates the expressions of several lipolytic enzyme genes, including brummer (bmm), lipase 3 (lip3), and hormone-sensitive lipase (hsl), and lipid storage droplet 1 (lsd1), a lipid droplets (LD)-associated protein gene. Further investigation in Drosophila reveals that salivary gland-specific knockdown of the dpp gene and fat body-specific knockdown of Mad involved in Dpp signaling phenocopy the effects of Bombyx dpp mutation on pupal development and lipolysis. Taken together, our data indicate that the Dpp-mediated BMP signaling in the fat body maintains lipid homeostasis by retarding lipolysis, which is necessary for pupa-adult transition during insect metamorphosis.

Vestigial suppresses apoptosis and cell migration in a manner dependent on the level of JNK-Caspase signaling in the Drosophila wing disc

The Decapentaplegic (Dpp) and Wingless (Wg) signal pathways play important roles in numerous biological processes in Drosophila. The Drosophila vestigial (vg) gene is selectively required for wing imaginal disc cell proliferation, which is essential for the formation of the adult wing and halter structures, and is regulated by Dpp and Wg signaling. Using a Drosophila invasion model of wing epithelium, we showed herein that inhibition of Dpp or Wg signaling promoted cells to migrate across the cell lineage restrictive anterior/posterior (A/P) compartment boundary. Being downstream of both Dpp and Wg signaling, vg can block cell migration induced by loss of either pathway. In addition, suppression of vg is sufficient to induce cell migration across the A/P boundary. Transcriptomic analysis revealed potential downstream genes involved in the cell migration after suppressing vg in the wing disc. We further demonstrated that the c-Jun N-terminal kinase (JNK) signaling promoted cell migration induced by vg suppression by upregulating Caspase activity. Taken together, our results revealed the requirement of Vg for suppressing cell migration and clarified how developmental signals collaborate to stabilize cells along the compartment boundary.