Progression through pupariation behaviours requires Dilp8-Lgr3 signalling between the epidermis and brain

ANDRÉS GARELLI

Buenos Aires

Congreso; LASDB Meeting - 2019; 2019

Sociedad Latinoamericana de Biología del Desarrollo

Holometabolan insects have evolved different behaviors and processes that promote survival during metamorphosis. Muscomorpha flies, such as Drosophila, metamorphose within a puparium, a protective structure consisting of the hardened cuticle of the last larval instar. Puparium formation (pupariation) is associated with additional survival-promoting behaviors, including the selection of a favorable pupariation site, extrusion of anterior spiracles for gas exchange, and attachment of the puparium to the substrate via expulsion of a salivary-gland-derived ?glue?. Proper survival through metamorphosis therefore requires tight coordination between these associated behavioral programs and the morphogenetic processes of pupariation: a set of body-reshaping motor programs and a cuticle sclerotization program that fixes the achieved morphological changes. Although the whole pupariation process is known to be triggered by the Ecdysone hormone, the downstream programs are thought to be mediated by specific neuroendocrine signals and circuits, most of which remain to be characterized. Here, we show that proper progression through a cascade of morphogenetic and behavioral pupariation programs, requires relaxin-like Dilp8-Lgr3 signaling between the cuticle epidermis and a novel subpopulation of thoracic neurons. This new role of the Dilp8-Lgr3 pathway is spatially and temporally independent of its known role in controlling the timing of the onset of pupariation in third instar larvae carrying abnormally growing imaginal discs. Detection of strong ilp8 expression in the cuticle of pupariating Ceratitis capitata larvae suggests this new pupariation-facilitating interorgan signaling event is conserved in Muscomorpha flies.