Progression Through Pupariation Behaviors Requires Dilp8-Lgr3 Signaling Between the Cuticle Epidermis and Thoracic CNS Neurons

ANDRES GARELLI,; PEREIRINHA, JOANA; HEREDIA, FABIANA; CASIMIRO, ANDREA; YANEL A VOLONTE; ALISSON M GONTIJO

Kolymbari, Creta

Congreso; Insect Hormones 2019; 2019

Higher dipterans undergo metamorphosis within a puparium, a protective capsulemade up of the reshaped and hardened cuticle of the last larval instar. Pupariumformation (pupariation) in Drosophila starts when wandering stage larvae reduce theirlocomotion and initiate increasingly strong whole body contractions that together withthe internalization of the three anteriormost body segments remodel the body andcuticle, reducing their length/width ratio from ~5 to ~3. This behavior lasts 5-10 minand culminates with the extrusion of a proteinaceous mix (glue) produced by thesalivary glands. The animal then slowly moves forward in a caterpillar-like fashion,traveling about half its length for ~1 min to its final pupariation site. We call thisbehavior glue-spreading behavior (GSB), as it helps to spread the glue over the ventralpart of the animal, promoting its attachment to the underlying substrate. FollowingGSB, the final shape of the puparium is set, even though weak and periodic contractionsoccur over the next 40-50 min (post-GSB), the operculum becomes defined, and thecuticle (i.e., the future puparium) starts to gradually sclerotize and tan. Here, we showthat proper progression through three pupariation behaviors (pre-GSB, GSB, and post-GSB) requires the Dilp8-Lgr3 pathway, a relaxin-like pathway that has been previouslyimplicated in controlling the timing of pupariation in animals carrying aberrantlygrowing imaginal discs. During pupariation, however, Dilp8-Lgr3 signaling is spatiallyandtemporally-distinct: a strong, epidermis-derived dilp8 expression peak that starts atthe pre-GSB phase of pupariation appears to signal via Lgr3 in a novel subpopulation ofthoracic CNS neurons. While this signaling ensures partial progression through the pre-GSB phase, and total progression through GSB and post-GSB phases, it is not requiredfor sclerotization and tanning. These results demonstrate a new transient epidermis toneuron signaling event that facilitates progression through the cascade of pupariationassociatedbehaviors.