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 Drosophila 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.
Subject(s)
Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , Ecdysone/pharmacology , Epidermis/metabolism , Morphogenesis/drug effects , Neurons/metabolism , Receptors, G-Protein-Coupled/metabolism , Animals , Drosophila/metabolism , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Ecdysone/genetics , Epidermal Cells/metabolism , Intercellular Signaling Peptides and Proteins , Larva/metabolism , Metamorphosis, Biological , Morphogenesis/genetics , Receptors, G-Protein-Coupled/genetics , Relaxin/metabolismABSTRACT
The New World Screwworm fly, Cochliomyia hominivorax, is a major pest of livestock in South America and Caribbean. However, few genomic resources have been available for this species. A genome of 534 Mb was assembled from long read PacBio DNA sequencing of DNA from a highly inbred strain. Analysis of molecular evolution identified 40 genes that are likely under positive selection. Developmental RNA-seq analysis identified specific genes associated with each stage. We identify and analyze the expression of genes that are likely important for host-seeking behavior (chemosensory), development of larvae in open wounds in warm-blooded animals (heat shock protein, immune response) and for building transgenic strains for genetic control programs including gene drive (sex determination, germline). This study will underpin future experiments aimed at understanding the parasitic lifestyle of the screwworm fly and greatly facilitate future development of strains for efficient systems for genetic control of screwworm.