Abstract
Innate behaviors consist of a succession of genetically-hardwired motor and physiological subprograms that can be coupled to drastic morphogenetic changes. How these integrative responses are orchestrated is not completely understood. Here, we provide insight into these mechanisms by studying pupariation, a multi-step innate behavior of fly larvae that is critical for survival during metamorphosis. We find that the steroid-hormone ecdysone triggers parallel pupariation neuromotor and morphogenetic subprograms, which include the induction of the relaxin-peptide hormone, Dilp8, in the epidermis. Dilp8 acts on six Lgr3-positive thoracic interneurons to couple both subprograms in time and to instruct neuromotor subprogram switching during behavior. Our work reveals that interorgan feedback gates progression between subunits of an innate behavior and points to an ancestral neuromodulatory function of relaxin signaling.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Figures and Supplementary Figures revised and updated as described below. Results, Discussion, and reference (9 new references added) sections revised to account for new data. New author included (Juliane Menezes). Text revised to improve clarity. Supplementary Fig. S1e was corrected form the inadvertent duplication of 1c. In total, we have added 30 new figure panels and new data to 7 panels. We now have 7 main Figures and 12 Extended Data Figures. Some Figures and Extended Data Figures had to be split as they became too large. The new Figure panels are: Fig. 2e, f, g, h (epidermal ecdysone receptor RNAi effects on puparium AR and dilp8 mRNA levels) Fig. 3d, e (epidermal dilp8 RNAi effects on puparium AR) Fig. 5i (epidermal dilp8 RNAi effects on GSB) Fig. 7n (effect of Lgr3 RNAi on ecdysone biosynthesis genes and genes downstream of ecdysone) Supplementary Fig. S1f, g, j, k. (new dilp8 RNAi line effects on AR, and CRM expression patterns) Supplementary Fig. S2g (lineage expression analysis of GAL4 lines in the epidermis) Supplementary Fig. S3c, d, i (no effect of fat-body dilp8 RNAi on AR and anterior retraction; no effect of pupal viability on puparium aspect ratio) Supplementary Fig. S4l (effect of Lgr3 on first and last pre-GSB contractions) Supplementary Fig. S5c, d (new Lgr3 background data) Supplementary Fig. S6d, e, f, g, h (post-GSB effects of Lgr3 mutation and post-GSB1-2 transition criteria) Supplementary Fig. S7a (epidermal EcR knockdown effect on GSB) Supplementary Fig. S11 (mhc>>GCaMP-fluorescence WT profile examples) Supplementary Fig. S12a, b, c, e (mhc>>GCaMP-fluorescence Lgr3 mutant profile examples) New data was added to panels: Fig. 5c, d, e (new Lgr3 data) Supplementary Fig. S4e, f, g, h (new Lgr3 background data)
